Menu
EN

Vyhledávání

Lidé

doc. RNDr. Jan Voves, CSc.

Všechny publikace

The atomistic model of electronic properties of Al2O3 and ZnO for the calculations of Al-doped ZnO

  • Autoři: Dadashov, R., doc. RNDr. Jan Voves, CSc.,
  • Publikace: Journal of Physics: Conference Series. Madeira: IOPscience, 2024. vol. 2701. ISSN 1742-6596.
  • Rok: 2024
  • DOI: 10.1088/1742-6596/2701/1/012096
  • Odkaz: https://doi.org/10.1088/1742-6596/2701/1/012096
  • Pracoviště: Katedra mikroelektroniky
  • Anotace:
    The final aim of this work is to simulate the electronic properties of Al-doped ZnO (AZO). The density-functional theory with the Coulomb interaction potential (DFT+U) method was used to specify the electronic properties of wurtzite ZnO: band structure and the density of states. The tool for structural and electronic simulation was QuantumATK, produced by Synopsys. The first part of the simulation was based on the modeling of the wurtzite ZnO periodic cell, which consisted of 108 atoms. We tried to get reasonable value of the band structure, which is from 3.30 to 3.37 eV according to experiments. The implementation of the Hubbard U method requires setting up accurate energy values for localized atomic orbitals. These values will help to establish an estimate of the Al-doped ZnO parameters. The same process was applied to Al!O"-α (corundum) in the second step. Based on this procedure, we have obtained estimated energy values for the 2p orbital for oxygen, the 3p orbital for aluminum, and the 3d orbital for zinc. AZO is used in solar cells as a transparent conducting layer. The percentage of the aluminum doping in ZnO does change its electrical and optical properties. If we can succeed in finding the appropriate percentage of aluminum for the doped material in the model, we can compare it with the experiment and use it in the photovoltaic systems as a transparent conductive layer.

A chemiresistive sensor array based on polyaniline nanocomposites and machine learning classification

  • DOI: 10.3762/bjnano.13.34
  • Odkaz: https://doi.org/10.3762/bjnano.13.34
  • Pracoviště: Katedra mikroelektroniky
  • Anotace:
    The selective detection of ammonia (NH3), nitrogen dioxide (NO2), carbon oxides (CO2 and CO), acetone ((CH3)2CO), and toluene (C6H5CH3) is investigated by means of a gas sensor array based on polyaniline nanocomposites. The array composed by seven different conductive sensors with composite sensing layers are measured and analyzed using machine learning. Statistical tools, such as principal component analysis and linear discriminant analysis, are used as dimensionality reduction methods. Five different classification methods, namely k-nearest neighbors algorithm, support vector machine, random forest, decision tree classifier, and Gaussian process classification (GPC) are compared to evaluate the accuracy of target gas determination. We found the Gaussian process classification model trained on features extracted from the data by principal component analysis to be a highly accurate method reach to 99% of the classification of six different gases.

Effect of HCl and H2SO4 Dilutant on Emeraldine Gas Sensor for Ammonia—Numerical Model

  • DOI: 10.1109/LSENS.2022.3210400
  • Odkaz: https://doi.org/10.1109/LSENS.2022.3210400
  • Pracoviště: Katedra mikroelektroniky
  • Anotace:
    Polyaniline changes its resistivity in the presence of various gas molecules, and therefore, it is currently studied for its deployment as a gas sensor, sensitivity to very small gas concentrations (lower than 1 ppm), selectivity to ammonia, nitrogen dioxide, or hydrogen, and long-term stability for thousands of voltage cycles. The preparation of this polymer is low cost using a very low pH environment where the polyaniline variety emeraldine base can be preceded to emeraldine salt, using hydrochloric acid, sulfuric acid, and others. After oxidative polymerization in the presence of an ammonium peroxidisulfate catalytic converter, the rest of the acid can be washed out. The effect of different acids on the final product emeraldine salt gas sensor conductivity was studied. One 32-mer-long polymer of emeraldine salt was simulated using QuantumATK as an electrical device, and its I−V characteristic was computed for pure polyaniline and polyaniline polluted by hydrochloric acid and sulfuric acid ions. The pollution concentration was 3 ppm. The results show that the resistance of polluted PANI increased a little for both acids. The results were compared with the recently published experimental data showing good accordance with them. The dilutants raise the resistance of the sensors, making them slightly less sensitive.

Electronic transport properties of compressed and stretched helicene-graphene nanostructures, a theoretical study

  • DOI: 10.1016/j.physe.2021.115111
  • Odkaz: https://doi.org/10.1016/j.physe.2021.115111
  • Pracoviště: Katedra mikroelektroniky
  • Anotace:
    We present our ab initio simulations of strained helicene molecular junction. First, we present ab-initio models of [n]helicenes up to [100]helicene done by two different recent reactive force field molecular geometry optimization methods (ReaxFF CHOCsKNaClIFLi, 2019 and CHONSMgPNaCuCl, 2018). We used the [4]helicene and [10]helicene models for Density Functional Theory (DFT) electronic transport calculations of various graphene-helicene-graphene molecular junction configurations on Local Density Approximation (LDA) or Generalized Gradient Approach (GGA) level of exchange and correlation energy with Perdew-Zinger (PZ) or Per-dew–Burke–Ernzerhof (PBE) functionals and Grimme DFT-D3 van der Waals correction. The electronic transport properties are studied by using of the Green’s functions formalism. The electron transmissions and densities of states of [4]helicene (and [10]helicene) attached as a molecular junction in three different configurations to zigzag graphene nanoribbon (ZGNR) electrodes of three different widths were obtained. The structures are analyzed while relaxed, compressed or stretched. The current-voltage and current-strain characteristics are presented and results are compared and discussed. The work is supported by a short review summarizing some of the recent studies related to graphene, helicene, and molecular junctions under strain.

Low-resistance ohmic contacts on boron-doped {113} oriented homoepitaxial diamond layers

  • DOI: 10.1016/j.diamond.2021.108797
  • Odkaz: https://doi.org/10.1016/j.diamond.2021.108797
  • Pracoviště: Katedra mikroelektroniky
  • Anotace:
    Refractory metals (titanium, molybdenum, and zirconium) with a gold overlayer were used to form ohmic contacts on {113}-oriented boron doped diamond epitaxial layers (boron concentration ranging from 1019 to 1021 cm−3). Morphology and thickness of deposited layers were determined by AFM and X-SEM; resistivity, carrier concentration and mobility were determined by Hall measurement. Specific contact resistance RCsp of evaporated Ti/Au, Zr/Au, and Mo/Au contacts was measured using c-TLM structures after different annealing stages at temperatures up to 850 °C. Results show that on layers with {113} orientation it is possible to achieve ohmic contacts of comparable quality as for layers with {100} orientation. For all three metal systems, the lowest values for specific contact resistance reached 1 × 10−6 Ω.cm2. Ti/Au contacts show a stable ohmic behavior over the whole range of annealing temperatures, while Mo/Ti contacts had to be annealed above 500 °C to reduce the Schottky barrier and achieve good ohmic contact on lower B doped layers. Zr/Au contacts exhibit the lowest adhesion and required annealing to at least 700 °C to achieve ideal electrical and mechanical properties. Mo/Au and Zr/Au contacts on highly boron doped layers (~1021 cm−3) show excellent contacts when annealed at 700 °C, and therefore can be considered as improved candidates for ohmic contacts for diamond-based high-temperature power electronics than the conventional Ti/Au (Ti/Pt/Au) contact system. In summary, this study confirms the suitability of {113} oriented boron doped diamond epitaxial layers for the fabrication of diamond power electronic devices with excellent ohmic contacts.

Modeling a multiple-chain emeraldine gas sensor for NH3 and NO2 detection

  • Autoři: Šustková, H., doc. RNDr. Jan Voves, CSc.,
  • Publikace: Beilstein Journal of Nanotechnology. 2022, 13 721-729. ISSN 2190-4286.
  • Rok: 2022
  • DOI: 10.3762/bjnano.13.64
  • Odkaz: https://doi.org/10.3762/bjnano.13.64
  • Pracoviště: Katedra mikroelektroniky
  • Anotace:
    This paper describes atomistic device models of a multiple-chain polyaniline (PANI) gas sensing component, utilizing the non-equilibrium Green’s functions formalism. The numerical results are compared with experimental data of ammonia and nitrogen dioxide detection. Multiple molecules of PANI in the form of emeraldine salt were studied with more than one absorbed molecule of ammonia or nitrogen dioxide. From the I–V characteristics of the system with and without adsorbed gas molecules for gas concentrations of 3, 6, 9, and 12 ppm, the effective resistance changes, (R − R0)/R0, were obtained and compared with experimental results. A good agreement with the measured values was obtained. In summary, PANI as emeraldine salt was numerically modeled for several adsorbed gas concentrations, several gas configurations, and different PANI molecule positions, including carrier hopping between them. The results are comparable to the experiment and show good properties for the application as gas sensor device for NH3 detection and rather good properties for NO2 detection.

Characterization of the Very Low Contact Resistance on Heavily Boron Doped (113) CVD Diamond

  • DOI: 10.37904/nanocon.2021.4320
  • Odkaz: https://doi.org/10.37904/nanocon.2021.4320
  • Pracoviště: Katedra mikroelektroniky
  • Anotace:
    The low resistance of ohmic contacts on diamond layers is important for the fabrication of diamond power electronic devices with fast switching capabilities for future high voltage applications. The low barrier height between the metal and diamond, high level of boron doping and annealing at elevated temperatures are the most critical parameters to reach the lowest contact resistivity. In this work, we report on titanium/gold ohmic contacts prepared on the heavily boron-doped (113) epitaxial diamond layers. The contact resistance has been characterized by the Circular Transmission Line Model (cTLM) structures. We used the analytical model of field enhanced emission, tunneling and the image force influence including Fermi level position dependence on the boron concentration for theoretical Ti/Au contact analysis and the Silvaco TCAD 2D simulation to estimate the measurement error associated with the nonzero metal resistance. We show that the resulting simulation values are consistent with the experimental results.

Effect of the substrate crystalline orientation on the surface morphology and boron incorporation into epitaxial diamond layers

  • DOI: 10.37904/nanocon.2020.3683
  • Odkaz: https://doi.org/10.37904/nanocon.2020.3683
  • Pracoviště: Katedra mikroelektroniky
  • Anotace:
    Epitaxial growth of diamond is critically important for the fabrication of diamond-based electronic devices. The emerging study of the epitaxial diamond growth on the (113) vicinal surfaces evidences highly needed high growth rates and low structural defects concentrations with both p- and n-type doping. In this work, we compare the morphology and dopant concentration incorporation of heavily boron-doped (113) epitaxial diamond layers with conventionally studied (100) and (111) epitaxial layers. Epitaxial layers were grown using resonance cavity Microwave Plasma Enhanced Chemical Vapor Deposition (MWPECVD) system. The surface morphology of epitaxial layers was studied by optical microscopy and atomic force microscopy, whereas the boron incorporation homogeneity was determined by Raman spectroscopy mapping. Heavily boron-doped (113) epitaxial diamond layers can be grown at a high growth rate with a smooth surface, without pyramidal hillocks or non-epitaxial crystallite defects, and with homogeneous boron concentration. These results confirm that epitaxial diamond growth on (113) vicinal surfaces is a promising solution for the development and fabrication of diamond-based electronic devices. (9) (PDF) Effect of the substrate crystalline orientation on the surface morphology and boron incorporation into epitaxial diamond layers. Available from: https://www.researchgate.net/publication/349892789_Effect_of_the_substrate_crystalline_orientation_on_the_surface_morphology_and_boron_incorporation_into_epitaxial_diamond_layers [accessed Aug 25 2021].

Properties of boron-doped (113) oriented homoepitaxial diamond layers

  • DOI: 10.1016/j.diamond.2020.108223
  • Odkaz: https://doi.org/10.1016/j.diamond.2020.108223
  • Pracoviště: Katedra mikroelektroniky
  • Anotace:
    Although significant efforts have been dedicated to optimize the quality of epitaxial diamond layers, reported properties of diamond based electronic devices do not yet approach expected theoretical values. Recent works indicate that boron-doped and phosphorous-doped diamond can be grown on atomically stepped (113) surfaces (A. Tallaire et al., 2016; M.-A. Pinault-Thaury et al., 2019), however the electrical properties of these layers have not been studied in detail. In this work, we report on structural and electrical properties of boron-doped epitaxial diamond layers grown on (113) substrates. Properties of the diamond layers have been investigated by means of scanning electron microscopy, atomic force microscopy, Hall effect, secondary ion mass spectrometry and Raman spectroscopy. Our results show that boron-doped diamond layers can be grown on (113) substrates at high deposition rates with atomically flat surfaces, excellent electrical properties and high boron incorporation efficiency.

Electronic Equivalent of Consciousness with Elementary Mental Process Model

  • Autoři: Polnický, R., Paulů, F., doc. RNDr. Jan Voves, CSc.,
  • Publikace: Proceedings of the 21st EANN (Engineering Applications of Neural Networks) 2020 Conference. Cham: Springer, 2020. p. 487-496. Proceedings of the International Neural Networks Society. vol. 2. ISSN 2661-8141. ISBN 978-3-030-48790-4.
  • Rok: 2020
  • DOI: 10.1007/978-3-030-48791-1_38
  • Odkaz: https://doi.org/10.1007/978-3-030-48791-1_38
  • Pracoviště: Katedra mikroelektroniky
  • Anotace:
    We present a project to design of the simplified model of thinking located in a little-explored field between neurobiology and psychology. While neurobiology in the incredibly complex microscopic system is dedicated to the structures and signals at the molecular level and the psychology is committed at the opposite extreme with highly sophisticated, they are very abstract and, therefore, difficult to grasp these wholes. There is a vast space between these two extremes. From the perspective of the inherent observers, it is investigable without overcoming the complexity of both points of interest. The primary goal of this research is to construct a multi-layer analog configuration space, the Electronic Equivalent of Consciousness (ECC), wherein the signals have the same properties (bioelectrical) as in the human brain.

Inkjet Seeded CVD-Grown Hydrogenated Diamond Gas Sensor Under UV-LED Illumination

  • DOI: 10.1109/JSEN.2019.2946947
  • Odkaz: https://doi.org/10.1109/JSEN.2019.2946947
  • Pracoviště: Katedra mikroelektroniky
  • Anotace:
    Hydrogen-terminated diamond gas sensors have been prepared by selective deposition of nanodiamond ink using direct inkjet printing on interdigital electrodes, followed by chemical vapor deposition growth of a nanoctrystalline diamond layer. The structure of the deposited layer was characterized and analyzed by scanning electron microscopy and Raman spectroscopy. The effect of ultraviolet light-emitting diode (UV-LED) illumination on the performance of the hydrogen-terminated diamond gas sensor with regard to reducing (NH3) and oxidizing (NO2) gases at various temperatures was studied. UV-LED illumination showed a short response/recovery time to NH3 and NO2 gases, 97 s / 153 s, and 72 s / 186 s, respectively.

Modelling current transport in boron-doped diamond at high electric fields including self-heating effect

  • Autoři: Lambert, N., Taylor, A., Hubík, P., Bulíř, J., More-Chevalier, J., Karaca, H., Fleury, C., doc. RNDr. Jan Voves, CSc., Šobáň, Z., Pogany, D., Mortet, V.
  • Publikace: Diamond and Related Materials. 2020, 2020 ISSN 0925-9635.
  • Rok: 2020
  • DOI: 10.1016/j.diamond.2020.108003
  • Odkaz: https://doi.org/10.1016/j.diamond.2020.108003
  • Pracoviště: Katedra mikroelektroniky
  • Anotace:
    In this work, current multiplication at high electric field in epitaxial boron-doped diamond with high acceptor concentration is analyzed, including self-heating effect and impurity impact ionization. Quasi-static current-voltage (I-V) characteristics were measured using a transmission-line pulse setup with 100 ns pulse duration on samples with two Ohmic titanium/gold electrodes. Unambiguous exponential and super-exponential behaviors are observed in the I-V curves along with, in some cases, negative differential resistance. The self-heating effect is analyzed using transient interferometric mapping of the thermal energy distribution between electrodes with a ns time scale. Measured I-V characteristics are modeled by finite element method and by considering boron acceptor ionization due to self-heating effect and impurity impact ionization. Simulated I-V characteristics, in particular the appearance of the negative differential resistance region attributed to self-heating, are in good agreement with experimental data.

MOSFETs’ Electrical Performance in the 160-nm BCD Technology Process With the Diamond Layout Shape

  • DOI: 10.1109/TED.2020.3000744
  • Odkaz: https://doi.org/10.1109/TED.2020.3000744
  • Pracoviště: Katedra mikroelektroniky
  • Anotace:
    This article introduces an innovative approach that describes the drain–source current improvements of MOS transistors. It is based on the geometrical modification of MOSFET’s channel from a rectangular layout shape (RLS) into a diamond layout shape (DLS). In this way, the drain–source current enhancement is increased up to 11% for the DLS MOS transistors with an effective aspect ratio (W/L)eff equal to 2.0 and an angle set to 80. Moreover, we present the comparison of 3-D TCAD simulations data, analytical model data based on Schwarz–Christoffel transformation (SCT), and measurement data given by the measurement of the MOS transistors fabricated in the Bipolar- CMOS-DMOS (BCD) 160-nm technology process. For this purpose, there have been fabricated 1124 samples, which were proportionally divided into RLS MOSFETs and DLS MOSFETs with the angles equal to 120, 100, and 80. For all studied aspect ratios, the presented model has an excellent analytic description in comparison with the 3-D TCAD simulation results with an error lower than 3%. So, it proves the quality of the analytical model based on the SCT approach and it is the recommended approach to use also for modeling other MOSFET gate layout shapes.

SELECTIVE SENSING OF VOLATILE ORGANIC COMPOUNDS VIA A TEMPERATURE MODULATION OF METAL OXIDE GAS SENSORS WITH PRINCIPAL COMPONENT ANALYSIS

  • Autoři: Ahmad, A., doc. RNDr. Jan Voves, CSc.,
  • Publikace: Proceedings 11th International Conference on Nanomaterials - Research & Application. Ostrava: Tanger, 2020. p. 262-266. ISSN 2694-930X. ISBN 978-80-87294-95-6.
  • Rok: 2020
  • DOI: 10.37904/nanocon.2019.8731
  • Odkaz: https://doi.org/10.37904/nanocon.2019.8731
  • Pracoviště: Katedra mikroelektroniky
  • Anotace:
    The measurements of volatile organic compounds are becoming more important due to stringent environmental regulations and increasing health concerns. The human breath which includes many volatile organic compounds that can be used as biomarkers for different diseases as well. Metal oxide (MOX) sensors are well known as multifunction nanomaterials and employing MOX in detecting VOCs is one of the most studied areas. The advantages of metal oxide sensors are well known as low costs, short response time and versatility. Currently, these sensors are sufficiently sensitive for most applications. However, the use of them is limited due to their lack of selectivity, which has stimulated researchers to look for different strategies to overcome this drawback. Sensing mechanisms of gas sensors depend on temperature, and this is, in particular, true for metal-oxide semiconductors where the peculiar role of temperature suggested the modulation of temperature as a viable method to tune selectivity and sensitivity. In this work, a device consisted of metal oxide gas sensor array has been used to discriminate different volatile organic compounds. The device consists of three MOX commercial sensors (ASMLN, AS-MLK, AS-MLC), The behavior of these sensors was measured at different ranges of temperature. By Principal Component Analysis (PCA) as a recognition algorithm and modulated temperature, selective sensing has been accomplished.

A High Sensitivity UV Photodetector With Inkjet Printed ZnO/Nanodiamond Active Layers

  • DOI: 10.1109/JSEN.2019.2893572
  • Odkaz: https://doi.org/10.1109/JSEN.2019.2893572
  • Pracoviště: Katedra mikroelektroniky
  • Anotace:
    The single- and double-layered photodetectorsbased on ZnO and/or detonation nanodiamond (DND) have beendeveloped via a sequential inkjet printing on the interdigital elec-trode platform using a diamond and zinc oxide precursor ink. Themorphological structure of the deposited materials was visualizedand analyzed by scanning electron microscopy and atomic forcemicroscopy. The crystalline configuration and structural qualityof ZnO and nanodiamond were investigated by X-ray diffractionand Raman spectroscopy. The response, response time, andrecovery time were measured for different UV wavelengths(365, 385, and 405 nm), light intensities, temperatures, and biasvoltages. The ZnO/DND structure shows more than ten timeshigher response and faster reactivity in comparison with a single-layered photodetector. Photoresponsivity of the double-layeredphotodetector (ZnO/DND) is 0.35 A/W, whereas bare ZnOis about 0.039 A/W. The interaction between UV light andZnO/DND grains was investigated by two dimensional SilvacoTCAD simulation.

Flexible ammonia gas sensor based on polyaniline

  • Pracoviště: Katedra mikroelektroniky
  • Anotace:
    In this paper we prepared flexible ammonia (NH3) gas sensor based on polyaniline (PAni) as an active sensing thin film layer. The sensors function was based on chemiresistive principle with thin film deposited on top of interdigitated electrodes. We measured the change in resistance of the thin film under gas exposure. The PET based foil has been used as the sensors substrate. The Interdigitated electrodes (IDE) has been printed with Fujifilm Dimatix DMP 2831 inkjet printer by nanocoloid silver ink. The active thin film has been prepared by drop casting method from polyaniline nanoparticle dispersion. The morphology of thin films surface was characterized by atomic force microscopy (AFM). The sensors response was investigated in a gas chamber and the gas flow was controlled by mass flow meters. The sensitivity towards various gases under different concentration in synthetic air has been tested. The tested gases were NH3, NO2, CO2 and CO. The measurement of the sensors response to the different levels of humidity was also conducted. All the measurements were performed at room temperature, which is important feature for the sensor to be able to operate in hazardous environment and it facilitates low-power operation of the sensor as well. We also observed the long-term stability of the sensors response, as well as the effect of bending of the sensing platform on the sensors response and stability.

Improvements in the Electrical Performance of IC MOSFET Components Using Diamond Layout Style Versus Traditional Rectangular Layout Style Calculated by Conformal Mapping

  • DOI: 10.1109/TED.2019.2931090
  • Odkaz: https://doi.org/10.1109/TED.2019.2931090
  • Pracoviště: Katedra mikroelektroniky
  • Anotace:
    In the first part of this article, we have proposed an innovative approach to improve the drain current model of the MOSFETs implemented with the diamond layout style (DLS), regarding the longitudinal corner effect (LCE). The proposed model is more accurate than a previous model compared to 3-D TechnologyComputer-AidedDesign (3-D TCAD) simulation results. The new model has an innovative analytical description based on a conformal mapping theory. As a conformal mapping, there has been chosen a Schwarz–Christoffel transformation (SC). The maximal deviation values of the aspect ratio calculated by LCE are in the range from −27% to +38%. In counterpart with the new SC analytical description of DLS, the maximal deviation values are in the range from 0% to −5.5%. The second part of this article describes improvements in the electrical performance of the N-MOSFET components by using DLS counterpart to traditional rectangular layout style (RLS). Both layout style DLS, RLS, respectively, have the same process settings, as well as they are keeping the same gate area A, and an aspect ratio width to length W/L to preserve the same input conditions for their analysis. The maximal drain current increasing for the simulated DLS MOS transistor is over 20% for effective aspect ratio (W/L)eff equal to 2.0 and the angle is set to 60 grads. The presented model has a very good analytic description with the error level lower than 3%.

Polyaniline emeraldine salt as an ammonia gas sensor - Comparison of quantum-based simulation with experiment

  • DOI: 10.1016/j.physe.2019.113621
  • Odkaz: https://doi.org/10.1016/j.physe.2019.113621
  • Pracoviště: Katedra mikroelektroniky
  • Anotace:
    Polyaniline as a conducting polymer is proposed to react with gas molecules and thus change its electrical conductivity. In this paper, a polyaniline molecule, in the form of emeraldine salt, and its electrical conductivity in or without the presence of NH3 were studied using numerical modelling. From the I-V characteristic of emeraldine salt molecule in the presence and without the presence of ammonia molecule, the effective resistance (R−R0)/R0 was computed and compared with experimental data. Because of only one molecule computation, I-V characteristics come to saturation (limited amount of charge carriers). The resistance is computed for pure polyaniline (PANI) and PANI with adsorbed ammonia molecule corresponding to approximative ammonia gas concentration of 3 ppm. The relative resistance increase was compared with experimental data and it was shown to be consistent with the measured values. From the results, PANI in the form of emeraldine salt is suitable as a sensing element in NH3 gas sensors.

Effective mass approximation versus full atomistic model to calculate the output characteristics of a gate-all-around germanium nanowire field effect transistor (GAA-GeNW-FET)

  • Autoři: Bayani, A.H., doc. RNDr. Jan Voves, CSc., Dideban, D.
  • Publikace: Superlattices and Microstructures. 2018, 133 769-776. ISSN 0749-6036.
  • Rok: 2018
  • DOI: 10.1016/j.spmi.2017.12.019
  • Odkaz: https://doi.org/10.1016/j.spmi.2017.12.019
  • Pracoviště: Katedra mikroelektroniky
  • Anotace:
    Here, we compare the output characteristics of a gate-all-around germanium nanowire field effect transistor (GAA-GeNW-FET) with 2.36 nm2 square cross-section area using tight-binding (TB) sp3d5s∗ model (full atomistic model (FAM)) and effective mass approximation (EMA). Synopsys/QuantumWise Atomistix ToolKit (ATK) and Silvaco Atlas3D are used to consider the TB model and EMA, respectively. Results show that EMA predicted only one quantum state (QS) for quantum transport, whereas FAM predicted three QSs. A cosine function behavior is obtained by both methods for the first quantum state. The calculated bandgap value by EMA is almost twice smaller than that of the FAM. Also, a fluctuating current is predicted by both methods but in different oscillation values.

Gas-sensing behaviour of ZnO/diamond nanostructures

  • DOI: 10.3762/bjnano.9.4
  • Odkaz: https://doi.org/10.3762/bjnano.9.4
  • Pracoviště: Katedra mikroelektroniky
  • Anotace:
    Microstructured single- and double-layered sensor devices based on p-type hydrogen-terminated nanocrystalline diamond (NCD) films and/or n-type ZnO nanorods (NRs) have been obtained via a facile microwave-plasma-enhanced chemical vapour deposition process or a hydrothermal growth procedure. The morphology and crystal structure of the synthesized materials was analysed with scanning electron microscopy, X-ray diffraction measurements and Raman spectroscopy. The gas sensing properties of the sensors based on i) NCD films, ii) ZnO nanorods, and iii) hybrid ZnO NRs/NCD structures were evaluated with respect to oxidizing and reducing gases at 150 °C. The hybrid ZnO NRs/NCD sensor showed a remarkably enhanced NO2 response compared to the ZnO NRs sensor. Further, inspired by this special hybrid structure, the simulation of interaction between the gas molecules (NO2 and CO2) and hybrid ZnO NRs/NCD sensor was studied using DFT calculations.

Performance Evaluation of Low-Cost Flexible Gas Sensor Array with Nanocomposite Polyaniline Films

  • DOI: 10.1109/JSEN.2018.2811461
  • Odkaz: https://doi.org/10.1109/JSEN.2018.2811461
  • Pracoviště: Katedra mikroelektroniky
  • Anotace:
    The aim of this paper is to present the design of a sensor array based on a single substrate with various composite polymer films as active layers for gas detection. A low power, four element flexible sensor platform with heater and temperature sensor was designed. The advantages of resistive sensors are easy fabrication, simple operation and low production cost. Composite polymer films exhibit good sensitivity to low gas concentrations at room temperatures. The principle of the designed sensor array is a change of electrical resistance in dependence of gas concentration. PANI, PANI/CNT, PANI/SnO2 and PANI/TiO2 composites were used as active layers. Gas sensing properties of active layers for NH3, CO2, NO2, O2, acetone, toluene and relative humidity were studied. PANI composites, unlike pristine PANI, exhibit good reversibility and lower temperature dependence.

Investigation of sub-10nm Cylindrical Surrounding Gate Germanium Nanowire Field Effect Transistor with Different Cross-Section Areas.

  • Autoři: Bayani, A., Dideban, D., doc. RNDr. Jan Voves, CSc., Moezi, N.
  • Publikace: Superlattices and Microstructures. 2017, 105 110-116. ISSN 0749-6036.
  • Rok: 2017
  • DOI: 10.1016/j.spmi.2017.03.020
  • Odkaz: https://doi.org/10.1016/j.spmi.2017.03.020
  • Pracoviště: Katedra mikroelektroniky
  • Anotace:
    Germanium nanowires (GeNWs) with different cross-sectional areas are considered as the channel of a cylindrical surrounding gate field effect transistors (CSGFETs) and the electronic properties of them are calculated through the density functional method and Slater-Koster (SK) tight binding model. The corresponding transistor parameters are obtained using Non-equilibrium Green’s function (NEGF) combined by SK model. We find that SK model predicts the well-nigh same bandgap value compared to meta-GGA-DFT approximation, while GGA-DFT underestimates the value of the bandgap. CSGGeNW-FETs Transistor figure of merit shows a supreme Ion/Ioff ratio which is equal to 10to12 for one of the considered structures with a circular cross-section. The obtained subthreshold swing (SS) values for the FETs illustrate an increment trend when the supercell size of the germanium nanowire increases whereas the transconductance and ON current of the FETs decrease when the GeNW supercell size scales down due to the declining of the density of states and electron transmission spectrum.

Simulation of Epitaxially Grown Graphene on Step-Shaped SiC Surface

  • Autoři: Barulin, A., Šmarhák, J., doc. RNDr. Jan Voves, CSc.,
  • Publikace: Proceedings of the 8th International Conference on Nanomaterials - Research and Application. Ostrava: Tanger, 2017. p. 110-115. ISBN 978-80-87294-71-0.
  • Rok: 2017
  • Pracoviště: Katedra mikroelektroniky
  • Anotace:
    In this study we present calculation of molecular mechanic and electronic transport properties of epitaxially grown graphene on step-shaped SiC substrate. We simulated two types of structural arrangements. The first structure, simulated mainly for purposes of comparisson, is planar SiC with graphene bilayer. The second structure is step-shaped SiC with graphene monolayer. We analyzed effects of hydrogenization of the SiC surface and conducted a series of calculations adressing shape of the resulting graphene layers. Finally, we calculated transmission spectrum and I/V curve of resulting structures.

Analysis of Finfet Characteristics with Gate Length Scalling

  • Autoři: Šustková, H., doc. RNDr. Jan Voves, CSc.,
  • Publikace: NANOCON 2014, 6TH INTERNATIONAL CONFERENCE. Ostrava: Technická universita Ostrava - Vysoká škola báňská, 2015. p. 814-819. ISBN 978-80-87294-53-6.
  • Rok: 2015
  • Pracoviště: Katedra mikroelektroniky
  • Anotace:
    The effect of gate length variations of a FinFET device (6 x 7 nm width and height) by performing 3D Silvaco TCAD simulations was investigated. In addition, comparative Atomistics ToolKit by QuantumWise simulations were done, with a view to TCAD / ATK functionality at quantum effects. Both systems use Non-Equilibrium Green Functions (NEGF) for electron quantum transport simulation. The ATK tool uses the real atom positions in the device crystal lattice for the Density Functional Theory (DFT) based calculations moreover. It is found that the gate length influences the drain current mostly for small voltages. Short gate transistors show the saturation current for clearly lower voltages, the saturation current for longer gates is achieved for higher voltages but get lower values. Electron transmission functionality of system's energy has been analyzed as well. The ATK uses more precise quantum models, but the time consumption is enormous for the relative large structures as FinFET. 3D TCAD quantum model is sufficient for the faster analysis of quantum semiconductor device.

Electronic Transport Properties of [6+Nx12] Annulene Nets

  • Autoři: Šmarhák, J., doc. RNDr. Jan Voves, CSc.,
  • Publikace: NANOCON 2014, 6TH INTERNATIONAL CONFERENCE. Ostrava: Technická universita Ostrava - Vysoká škola báňská, 2015. p. 235-239. ISBN 978-80-87294-53-6.
  • Rok: 2015
  • Pracoviště: Katedra mikroelektroniky
  • Anotace:
    We analyzed electronic transport properties of graphene nanoribbons (GNR) patterned by [6+Nx12] annulene-like quantum antidots. We tried to simulate [18] annulene, [30] annulene and [42] annulene antidots placed on passivated graphene nanoribbon of appropriate width and length. Our results are predicting electronic transport properties similar to graphene. It is shown by analyzing the GNR transmissivities calculated by Extended Huckel self-consistent field model (EH-SCF). These structures can be used in future as a high precision molecular sieve for separation of almost any size of molecule because of its holes modifiable by using different [6+Nx12] annulenes. The sieving can be potentially controlled and/or measured by the changes of potential and/or current flow in chosen GNR layer of the sieve. These structures can be potentially usable for water desalinization, separation of industrially exhaled gases or for mining rare metals from ocean. It can be used as well as a totally new carbon-based nanomaterial with potentially interesting mechanical, optical or electronic transport properties and compatible with graphene. These structures can be prepared by the means of ion (or electron) beam lithography or by the bottom-up approach from chemical precursors in the future.

Simulation of Electron Transport in Helicenes

  • Autoři: Šmarhák, J., doc. RNDr. Jan Voves, CSc.,
  • Publikace: NANOCON 2015: 7TH INTERNATIONAL CONFERENCE ON NANOMATERIALS - RESEARCH & APPLICATION - Conference Proceedings. Ostrava: Tanger, 2015. p. 178-181. ISBN 978-80-87294-63-5.
  • Rok: 2015
  • Pracoviště: Katedra mikroelektroniky
  • Anotace:
    Helicenes attract attention as simple models for screw-shaped biomolecules, such as proteins and nucleic acids. Recently, they have been recognized as potential building blocks in nanomaterial sciences and the interest in their chemistry and physico-chemical properties has remarkably increased. Thus, helicenes represent an attractive objective for further research in various branches of chemistry and nanoscience. For mechanical and electrical simulation of helicenes we used Atomistix ToolKit licensed by QuantumWise. It is combining DFT and NEGF for ab initio and semi-empirical calculations of structure and electron transport. We simulated molecular mechanics and basic electronic properties of [49] helicene structure in standalone and two electrode configuration. Electron density and electron transmisivities of this structure has been analyzed.

A Perfect Lens for Ballistic Eectrons: An Electron-Light Wave Analogy

  • DOI: 10.1016/j.photonics.2013.08.005
  • Odkaz: https://doi.org/10.1016/j.photonics.2013.08.005
  • Pracoviště: Katedra elektromagnetického pole, Katedra mikroelektroniky
  • Anotace:
    The analogy between electromagnetic waves and ballistic electrons within the Kane's model is developed and subsequently applied to a theoretical description of a quantum version of a metamaterial planar lens. Restrictions imposed on the perfect lens and the poor man's lens by available semiconductor band structures are discussed. A realistic implementation is proposed for the quantum poor man's lens, which uses specific properties of the HgTe compound. The properties of the lens are presented on the basis of a calculated transmission of oblique electrons through the lens structure.

Analysis of Finfet Characteristics with Gate Length Scalling

  • Autoři: Šustková, H., doc. RNDr. Jan Voves, CSc.,
  • Publikace: NANOCON 2014 Conference Proceedings. Ostrava: Technická universita Ostrava - Vysoká škola báňská, 2014. ISBN 978-80-87294-55-0.
  • Rok: 2014
  • Pracoviště: Katedra mikroelektroniky
  • Anotace:
    The effect of gate length variations of a FinFET device (6 x 7 nm width and height) by performing 3D Silvaco TCAD simulations was investigated. In addition, comparative Atomistics ToolKit by QuantumWise simulations were done, with a view to TCAD / ATK functionality at quantum effects. Both systems use Non- Equilibrium Green Functions (NEGF) for electron quantum transport simulation. The ATK tool uses the real atom positions in the device crystal lattice for the Density Functional Theory (DFT) based calculations moreover. It is found that the gate length influences the drain current mostly for small voltages. Short gate transistors show the saturation current for clearly lower voltages, the saturation current for longer gates is achieved for higher voltages but get lower values. Electron transmission functionality of system's energy has been analyzed as well. The ATK uses more precise quantum models, but the time consumption is enormous for the relative large structures as FinFET. 3D TCAD quantum model is sufficient for the faster analysis of quantum semiconductor device.

SiC graphene FET with polydimethylglutharimide as a gate dielectric layer

  • Autoři: Náhlík, J., Šobáň, Z., doc. RNDr. Jan Voves, CSc., Jurka, V., Vašek, P.
  • Publikace: 10th International Conference on Advanced Semiconductor Devices and Microsystems ASDAM 2014 Conference Proceedings. Bratislava: Slovak University of Technology in Bratislava, 2014. p. 33-36. ISSN 2475-2916. ISBN 978-1-4799-5475-9.
  • Rok: 2014
  • DOI: 10.1109/ASDAM.2014.6998639
  • Odkaz: https://doi.org/10.1109/ASDAM.2014.6998639
  • Pracoviště: Katedra mikroelektroniky
  • Anotace:
    Graphene is perspective material for future carbon based electronics, flexible electronics and other applications. The necessary condition for the commercial use is the high quality graphene growth and semiconductor technology compatible process of whole field effect transistor (FET). One of suitable method for large scale graphene monolayer preparation is the thermal annealing of semi-insulating SiC substrate. One important task of graphene FET process is reliable, cheap and simple gate structure preparation. In this work we present our results of using MicroChem Lift-Off Resist (LOR) layer as a dielectric layer for SiC graphene FETs. LOR resist is based on polydimethylglutharimide. Its unique properties enable to perform exceptionally well resolution imaging, easy process tuning, high yields and superior deposition line width control. In the case of polymer based dielectric layers the breakdown voltage is important parameter. We prepared two sets of different capacitor structures with LOR dielectric layer and Au/Cr electrodes. The first set exhibits very low breakdown voltages (about 3 V). The optimisation of the LOR layer deposition process in the second set increased the breakdown voltage over 40 V keeping the leakage current lower than 2 nA. The second process with LOR layer was used for the preparation of graphene FETs on SiC substrates. The first measurements show resistivity dependence on gate voltage.

The Study of Graphene Gas Sensor

  • DOI: 10.4028/www.scientific.net/KEM.605.495
  • Odkaz: https://doi.org/10.4028/www.scientific.net/KEM.605.495
  • Pracoviště: Katedra mikroelektroniky
  • Anotace:
    The graphene is suitable for gas sensing applications for its two dimensional character which gives the best possible ratio between sensor surface and volume. The interaction between graphene surface and gas molecules can significantly change the graphene layer transport properties. Therefore graphene can serve as a sensitive layer in a gas sensor. This work is concentrated on the analysis of the conductivity of graphene layer exposed to different gases (NH3, CO2 etc.). Together with the electrical measurement on the interdigital graphene sensor a simulation based on quantum atomistic approach has been performed. We used ATK toolkit by Quantuwise based on density functional theory (DFT) models. The exchange-correlation potential is approximated within the generalized gradient approximation (GGA). The transport properties of the electrode-device-electrode geometry were calculated by means of non-equilibrium Green’s function formalism as implemented in ATK. Experimental conductivity changes are compared with the simulation results

A Perfect Lens for Ballistic Electrons

  • Autoři: Hrebíková, I., doc. Ing. Lukáš Jelínek, Ph.D., doc. RNDr. Jan Voves, CSc., Baena, J. D.
  • Publikace: Proceedings of Metamaterials´ 2013: The 7th International Congress on Advanced Electromagnetic Materials in Microwaves and Optics. Louvain-la-Neuve: UCL, Laboratoire d´Hyperfréquences, 2013. ISBN 978-952-67611-5-2.
  • Rok: 2013
  • Pracoviště: Katedra elektromagnetického pole, Katedra mikroelektroniky
  • Anotace:
    The analogy between plane electromagnetic waves and electron waves is presented and subsequently applied to the description of a quantum perfect lens. The natural constraints resulting from available semiconductor compounds are discussed. The final lens design relies on the inverted bandstructure of the HgTe compound, and uses a voltage gate to created the lens structure.

Spin Filtering Ability of Patterned Graphene Nanoribbons

  • Autoři: Šmarhák, J., doc. RNDr. Jan Voves, CSc.,
  • Publikace: 5th International Conference NANOCON 2013 Conference Proceedings. Ostrava: Technická universita Ostrava - Vysoká škola báňská, 2013. p. 113-117. ISBN 978-80-87294-47-5.
  • Rok: 2013
  • Pracoviště: Katedra mikroelektroniky
  • Anotace:
    The passivated zigzag graphene nanoribbons composed of 2 or 4 atoms wide basis (2-ZGNR or 4-ZGNR) produce strong spin-dependent behavior resulting in a large spin polarization effect. It is shown by analyzing the GNR transmissions calculated by Extended Hückel self-consistent field model (EH-SCF). Our results endorse that for the generation of spin-polarized currents, formation of spin-ordered edge-localized states along the zigzag edges is the key mechanism. We analyzed the influence of various point and planar defects as well as the influence of width and structural composition of GNRs and presented transmission, eigenstates, difference electron densities and electrostatic difference potentials of all respective structures. Since GNRs have long spin-correlation lengths and good ballistic transport characteristics they can be considered as a promising active material of spintronic devices without the need of ferromagnetic electrodes or other magnetic entities. The spin filtering structures could be prepared by the nanolithography of GNR or by the bottom-up approach in future.

AFM LOCAL ANODIC OXIDATION ON GRAPHENE

  • Autoři: Janoušek, M., Náhlík, J., Šobáň, Z., doc. RNDr. Jan Voves, CSc., Kalbáč, M., Jurka, V.
  • Publikace: Nanocon 2012. Ostrava: Technická universita Ostrava - Vysoká škola báňská, 2012. 1. ISBN 978-80-87249-32-1.
  • Rok: 2012
  • Pracoviště: Katedra mikroelektroniky
  • Anotace:
    Graphene is extensively studied attractive material for its remarkable electronic and mechanical properties. Local anodic oxidation (LAO) by means of atomic force microscope (AFM) with a conductive tip is a method used for device patterning in the nanometer scale at laboratory conditions. It represents a clean alternative to up-to-date nano-lithographic techniques as electron beam lithography (EBL) and nanoimprint lithography (NIL). Oxidation reaction between the tip and a conductive substrate creates an oxide line, which acts as a potential barrier. It enables to make narrow constrictions of 20 nm in width. We applied LAO on single-layer graphene CVD grown on copper foil and graphene grown on SiC prepared by high temperature annealing. Under optimum conditions for LAO the graphene oxide is created. The thickness of the oxide line depends on various parameters e.g. a tip bias, speed of the tip and ambient relative humidity.

Hydrogen silsesquioxane as a gate dielectric layer for SiC graphene FET

  • Autoři: Náhlík, J., Janoušek, M., Šobáň, Z., doc. RNDr. Jan Voves, CSc., Jurka, V., Macháč, P.
  • Publikace: ASDAM 2012. Bratislava: STU v Bratislave, FEI, 2012. p. 251-254. ISBN 978-1-4673-1195-3.
  • Rok: 2012
  • Pracoviště: Katedra mikroelektroniky
  • Anotace:
    Graphene can be prepared by annealing of SiC wafer. That allows large scale patterning by standard UV photolithography. Unfortunately SiC substrate does not allow back-gating in contrast to graphene on silicon substrate (with thin silicon dioxide layer). The major challenge is to find suitable dielectric layer that can be used for electrostatic gating without significant influence on carrier mobility or another properties of graphene. We examined electrical behavior of electron exposed hydrogen silsesquioxane (HSQ) layer used as dielectric layer of top-gated SiC graphene.

ELECTRICAL AND AFM STUDY OF DIFFERENT TYPES OF GRAPHENE

  • Autoři: Náhlík, J., Janoušek, M., doc. RNDr. Jan Voves, CSc.,
  • Publikace: NANOCON 2011 Conference Proceedings. Ostrava: Technická universita Ostrava - Vysoká škola báňská, 2011. pp. 481-485. ISBN 978-80-87294-23-9.
  • Rok: 2011
  • Pracoviště: Katedra mikroelektroniky
  • Anotace:
    We present our results of the atomic force microscope (AFM) surface analysis of graphene layers prepared by different methods. We compared surfaces of exfoliated graphene, graphene grown CVD on copper foil and graphene prepared by high temperature annealing of SiC. The CVD grown graphene layers were characterized electrically. We measured the sheet resistance of the layers in the presence of gate voltage applied on the bottom electrode realized by the conducting silicon substrate isolated by the silicon oxide layer.

Litografie nové generace pro nanometrové rozměry

  • Pracoviště: Katedra mikroelektroniky
  • Anotace:
    Přehled moderních litografických metod od fotolitografie přes bezmaskové a alternativní metody.

Metamaterial-inspired Perfect Tunnelling in Semiconductor Heterostructures

  • DOI: 10.1088/1367-2630/13/8/083011
  • Odkaz: https://doi.org/10.1088/1367-2630/13/8/083011
  • Pracoviště: Katedra elektromagnetického pole, Katedra mikroelektroniky
  • Anotace:
    In this paper, we use a formal analogy of the electromagnetic wave equation and the Schrödinger equation in order to study the phenomenon of perfect tunnelling (tunnelling with unitary transmittance) in a one-dimensional semiconductor heterostructure. Using the Kane model of a semiconductor, we show that this phenomenon can indeed exist, resembling all the interesting features of the corresponding phenomenon in classical electromagnetism in which metamaterials (substances with negative material parameters) are involved. We believe that these results can pave the way toward interesting applications in which metamaterial ideas are transferred into the semiconductor domain.

Perfect Tunneling in Semiconductor Heterostructures

  • Autoři: doc. Ing. Lukáš Jelínek, Ph.D., Baena, J.D., doc. RNDr. Jan Voves, CSc., Marques, R.
  • Publikace: Proceedings of Metamaterials´ 2011: The Fifth International Congress on Advanced Electromagnetic Materials in Microwaves and Optics. Louvain-la-Neuve: UCL, Laboratoire d´Hyperfréquences, 2011. pp. 1021-1023. ISBN 978-952-67611-0-7.
  • Rok: 2011
  • Pracoviště: Katedra elektromagnetického pole, Katedra mikroelektroniky
  • Anotace:
    We study the phenomenon of perfect tunneling (tunneling with unitary transmittance) in a 1D semiconductor heterostructure using a formal analogy of the electromagnetic wave equation and the Schrodinger equation. The Kane model of a semiconductor is used and it is shown that this phenomenon can indeed exist, resembling all the interesting features of the corresponding phenomenon in classical electromagnetism in which metamaterials are involved.

Spin-Dependent Transport Properties of Graphene Nanoribbons

  • Autoři: doc. RNDr. Jan Voves, CSc.,
  • Publikace: 17th Conference of Czech and Slovak Physisists. Bratislava: Slovenská fyzikálna spoločnosť, 2011. pp. 147-148. ISBN 978-80-970625-4-5.
  • Rok: 2011
  • Pracoviště: Katedra mikroelektroniky
  • Anotace:
    The graphene nanoribbons (GNR) lateral asymmetry produces strong spin-dependent behavior resulting in a large spin polarisation effect. It is shown by analyzing the GNR trasmissivities calculated by density-functional theory. Our results endorse that for the generation of spin-polarized currents, formation of spin-ordered edge-localized states along the zigzag edges is the key mechanism.

Graphene Nanoribbons Transport Properties Calculation

  • Autoři: doc. RNDr. Jan Voves, CSc.,
  • Publikace: NANOCON 2010 WoS. Ostrava: Technická universita Ostrava - Vysoká škola báňská, 2010. pp. 83-88. 1. ISBN 978-80-87294-19-2.
  • Rok: 2010
  • Pracoviště: Katedra mikroelektroniky
  • Anotace:
    We performed density-functional theory (DFT) based calculations to obtain electronic structure of both zig-zag and armchair GNRs with lateral constrictions. The spin-dependent exchange-correlation potential is approximated within the generalized gradient approximation using the QuantumWise toolkit ATK, which employs local numerical double-zeta polarized basis orbitals. The spin-dependent transport properties of the electrode-device-electrode geometry were calculated by means of non-equilibrium Green's function formalism as implemented in ATK. Band structures calculated by the DFT were compared with results of the semi-empirical method (Extended Huckel model). Our results show that GNRs with the constrictions exhibit novel transport properties. The horizontal layout of the GNR constrictions determines main features important for electrical and spintronic applications of these structures.

Graphene Nanoribbons Transport Properties Calculation

  • Pracoviště: Katedra mikroelektroniky
  • Anotace:
    The spin-dependent exchange-correlation potential is approximated within the generalized gradient approximation using the QuantumWise toolkit ATK, which employs local numerical double-zeta polarized basis orbitals. The spin-dependent transport properties of the electrode-device-electrode geometry were calculated by means of non-equilibrium Green's function formalism as implemented in ATK. Band structures calculated by the DFT were compared with results of the semi-empirical method (Extended Huckel model). Our results show that GNRs with the constrictions exhibit novel transport properties. The horizontal layout of the GNR constrictions determines main features important for electrical and spintronic applications of these structures. The constrictions could be realized by means of local anodic oxidation using scanning probe microscope.

Lithography on GaMnAs layer by AFM local anodic oxidation in the AC mode

  • Autoři: Janoušek, M., Halada, J., doc. RNDr. Jan Voves, CSc.,
  • Publikace: Microelectronic Engineering. 2010, 87(5-8), 1066-1069. ISSN 0167-9317.
  • Rok: 2010
  • DOI: 10.1016/j.mee.2009.11.085
  • Odkaz: https://doi.org/10.1016/j.mee.2009.11.085
  • Pracoviště: Katedra mikroelektroniky
  • Anotace:
    The results on the local anodic oxidation (LAO) by conductive coated tip of an atomic force microscope (AFM) are presented. AFM LAO with modulated voltage (AC mode) on thin GaMnAs layer is performed. Oxide lines produce potential barrier capable to make narrow constrictions for charge carriers. Oxide line height dependence on various parameters of the oxidation process is studied. Improvement in the homogeneity and reproducibility of oxide lines is observed. Lines up to 30 nm high are obtained. Magnetotransport measurement on constricted samples is realized.

Analysis of the resonant tunneling diode with the stepped prebarrier

  • Autoři: Yatskiv, R., doc. RNDr. Jan Voves, CSc.,
  • Publikace: Journal of Physics: Conference Series. 2009, 193(1), 012007-012010. ISSN 1742-6588.
  • Rok: 2009
  • DOI: 10.1088/1742-6596/193/1/012007
  • Odkaz: https://doi.org/10.1088/1742-6596/193/1/012007
  • Pracoviště: Katedra mikroelektroniky
  • Anotace:
    Resonant-tunnelling diodes (RTD) incorporating an emitter stepped pre-barrier are studied both theoretically and experimentally. The simulation of I-V characteristics of modified AlAs-GaAs double barrier RTD grown by molecular beam epitaxy with the stepped pre-barrier is presented. An 1D quantum transport simulator Wingreen based on the nonequilibrium Green functions (NEGF) is used in our case. Our result show that the coupling between energy levels in the emitter quantum-well and the main quantum well leads to the plateau behaviour of the I-V curves. The two plateau regions on the I-V characteristics have been observed in experimental and simulation results.

Nanoelectronics and nanolithography

  • Autoři: doc. RNDr. Jan Voves, CSc.,
  • Publikace: Nanocon 2009 Conference Proceedings. Ostrava: Technická universita Ostrava - Vysoká škola báňská, 2009. ISBN 978-80-87294-13-0.
  • Rok: 2009
  • Pracoviště: Katedra mikroelektroniky
  • Anotace:
    The local anodic oxidation (LAO) by the atomic force microscope (AFM) in the AC mode could be a good alternative to standard lithographic techniques especially for the device patterning in the nanometer scale at laboratory conditions. In the combination with EBL the nanostructures with the resolution of a few tenths of nanometers could be prepared in a very fast and efficient way.

Nanostructures defined by the local oxidation of the ferromagnetic GaMnAs layer

  • Autoři: doc. RNDr. Jan Voves, CSc., Šobáň, Z., Janoušek, M., Komarnitskyy, V., Cukr, M., Novák, V.
  • Publikace: Microelectronics Journal. 2009, 40(4-5), 697-705. ISSN 0026-2692.
  • Rok: 2009
  • DOI: 10.1016/j.mejo.2008.07.039
  • Odkaz: https://doi.org/10.1016/j.mejo.2008.07.039
  • Pracoviště: Katedra mikroelektroniky
  • Anotace:
    The results of local anodic oxidation (LAO) on the thin GaMnAs layers are reported. The ferromagnetic GaMnAs layers were prepared by low-temperature molecular beam epitaxy (MBE) growth in a Veeco Mod Gen II machine. The LAO process was performed with the atomic force microscope (AFM) Smena NT-MDT placed in the sealed box with the controlled humidity in the range 45-80%. The oxide was grown in the semi-contact mode of the AFM. The sample was positively biased with respect to the AFM tip with the bias from 6 to 24V. The conductive diamond-coated AFM tips with the radius 30nm were utilized for the oxidation. The tip speed during the oxidation was changed from 400 nm/s to 1.5 mm/s. The tip force was also changed during the oxidation. The height of oxide nanolines increases with applied voltage from 3 to 18 nm. The width of these lines was approximately 100 nm at half-maximum.

The AFM LAO lithography on GaMnAs layers

  • Autoři: doc. RNDr. Jan Voves, CSc., Cukr, M., Novák, V.
  • Publikace: Microelectronic Engineering. 2009, 86(4-6), 561-564. ISSN 0167-9317.
  • Rok: 2009
  • DOI: 10.1016/j.mee.2008.11.035
  • Odkaz: https://doi.org/10.1016/j.mee.2008.11.035
  • Pracoviště: Katedra mikroelektroniky
  • Anotace:
    atomic force microscope (AFM). These oxide lines, produced by the negatively biased AFM tip, formed the electrical barrier to the conducting holes in the layer. The constricted samples were characterized at low temperature (12 K). They showed magnetoresistance effect specific for nanoconstrictions during in-plane magnetic field sweep in both polarities for the different mutual orientation of magnetic field and current. The LAO appears to become a useful patterning technique for research of ferromagnetic semiconductor nanostructures. Further optimization of LAO parameters for reaching better homogeneity of the oxide lines is needed.

The characterization of the hole transport in Sb based strained quantum wells

  • Autoři: Šobáň, Z., doc. RNDr. Jan Voves, CSc., Kalna, K.
  • Publikace: Journal of Physics: Conference Series. 2009, 193(1), 012128-012131. ISSN 1742-6588.
  • Rok: 2009
  • DOI: 10.1088/1742-6596/193/1/012128
  • Odkaz: https://doi.org/10.1088/1742-6596/193/1/012128
  • Pracoviště: Katedra mikroelektroniky
  • Anotace:
    Compressively strained InSb structures aimed for p-channel heterostructure field effect transistors (HFETs) are analysed in order to maximise their hole mobility. We optimise the heterostructure by the change of the material composition, thickness of the layers and position of !-doping. The splitting of light and heavy hole bands in compressively strained channels are calculated by nextnano3 software as a function of material mole fraction and quantum well thickness. The 8 x 8 k.p method is used for the determination of corresponding hole eigenvalues. The strained layer bandstructure calculation is carried out with Quantumwise ATK for the Kohn-Sham DFT using double-zeta polarised basis set orbitals as well.

Hole transport in the p-type RTD

  • Autoři: Šobáň, Z., doc. RNDr. Jan Voves, CSc., Cukr, M., Novák, V.
  • Publikace: ASDAM 2008 Conference Proceedings. Bratislava: Slovak University of Technology, 2008. pp. 251-254. ISBN 978-1-4244-2325-5.
  • Rok: 2008

Optical Characterisation of MOVPE Grown Vertically Correlated InAs/GaAs Quantum Dots

InAs/GaAs quantum dot structures covered by InGaAs strain reducing layer characterised by photomodulated reflectance

  • Pracoviště: Katedra mikroelektroniky
  • Anotace:
    InAs/GaAs quantum dot structures covered by InGaAs strain reducing layer characterised by photomodulated reflectance

Local anodic oxidation of GaMnAs layers

  • Autoři: Jelínek, M., doc. RNDr. Jan Voves, CSc., Komarnitskyy, V., Cukr, M., Novák, V.
  • Publikace: Acta Metallurgica Slovaca Spec.Issue. 2007, 13(6), 117-122. ISSN 1335-1532.
  • Rok: 2007

Micromagnetic simulation of ferromagnetic nanostructures

  • Autoři: doc. RNDr. Jan Voves, CSc.,
  • Publikace: Acta Metallurgica Slovaca Spec.Issue. 2007, 13(6), 76-82. ISSN 1335-1532.
  • Rok: 2007

Nanostructures Defined by The Local Oxidation of Ferromagnetic GaMnAs Layer

  • Autoři: doc. RNDr. Jan Voves, CSc., Jelínek, M., Cukr, M., Novák, V., Šobáň, Z., Komarnitskyy, V.
  • Publikace: European Nano Systems. Grenoble: CMP, 2007. pp. 85-90. ISBN 978-2-35500-003-4.
  • Rok: 2007
  • Pracoviště: Katedra mikroelektroniky
  • Anotace:
    The results of Local Anodic Oxidation (LAO) on the thin GaMnAs layers are reported. The ferromagnetic GaMnAs layers were prepared by low temperature MBE growth in a Veeco Mod Gen II machine. The LAO process was performed with the AFM microscope Smena NT-MDT placed in the sealed box with the controlled humidity in the range 45-80%. The oxide was grown in the semi-contact mode of the AFM. Sample was positively biased with respect to the AFM tip with the bias from 6 to 24 V. The conductive diamond coated AFM tips with the radius 30 nm were utilized for the oxidation. The tip speed during the oxidation was changed from 400 nm/s to 1.5 um/s. The tip force was also changed during the oxidation. The height of oxide nanolines increases with applied voltage from 3 to 18 nm. The width of these lines was approximately 100 nm at half of the maximum.

NEGF simulation of the RTD bistability

  • Autoři: doc. RNDr. Jan Voves, CSc., Yatskiv, R., Třebický, T.
  • Publikace: Journal of Computational Electronics. 2007, 6(1-3), 259-262. ISSN 1569-8025.
  • Rok: 2007
  • Pracoviště: Katedra mikroelektroniky
  • Anotace:
    The simulation of I-V characteristics of Al0.3Ga0.7As-GaAs and AlAs-GaAs resonant tunneling diodes (RTD) is presented. The nonequilibrium Green function (NEGF) based 1D quantum transport simulator Wingreen is used in our case. The plateau region on the IV characteristics usually present only by the Wigner function equation (WFE) based simulation appeared now by the NEGF simulation of our AlAs-GaAs RTD and its shape is comparable with our experimental measurements.

OPTICAL CHARACTERISATION OF MOVPE GROWN ENGINEERED InAs/GaAs QUANTUM DOT STRUCTURES

  • Autoři: prof. Ing. Pavel Hazdra, CSc., doc. RNDr. Jan Voves, CSc., Oswald, J., Kuldová, K., Hospodková, A., Hulicius, E., Pangrác, J.
  • Publikace: Proceedings of Workshop 2007. Praha: České vysoké učení technické v Praze, 2007. pp. 252-253. ISBN 978-80-01-03667-9.
  • Rok: 2007
  • Pracoviště: Katedra mikroelektroniky
  • Anotace:
    OPTICAL CHARACTERISATION OF MOVPE GROWN ENGINEERED InAs/GaAs QUANTUM DOT STRUCTURES

Nanotechnologie a jejich aplikace v elektronice

  • Autoři: doc. RNDr. Jan Voves, CSc.,
  • Publikace: 12. mezinárodní konference Moderní elektronické součástky. Praha: Sdělovací technika, 2006. pp. 1-83.
  • Rok: 2006

NEGF Simulation of the RTD Bistability

  • Autoři: doc. RNDr. Jan Voves, CSc., Yatskiv, R., Třebický, T.
  • Publikace: Book of Abstracts: 11th International Workshop on Computational Electronics. Wien: Technische Universität, 2006. ISBN 3-901578-16-1.
  • Rok: 2006
  • Pracoviště: Katedra mikroelektroniky
  • Anotace:
    Nonequilibrium Green function simulation of the resonant tunneling diode bistability

Optical characterisation of MOVPE grown vertically correlated InAs/GaAs quantum dots

  • Pracoviště: Katedra mikroelektroniky
  • Anotace:
    Paper deals with optical characterisation of MOVPE grown vertically correlated InAs/GaAs quantum dots

Optical Properties of Subnanometric InAs Structures in GaAs Grown by MOVPE

  • Pracoviště: Katedra mikroelektroniky
  • Anotace:
    Optical Properties of Subnanometric InAs Structures in GaAs Grown by MOVPE

Semiconductor ferromagnetic nanodevices

  • Pracoviště: Katedra mikroelektroniky
  • Anotace:
    Semiconductor spintronics has reached a stage where the basic physical mechanisms controlling spin injection and detection are understood. Moreover, some critical technological issues involved in the growth and lithography of the magnetic semiconductors have been solved. This has allowed to explore the physics of spintronic nanostructures. As examples of such devices, magnetic resonant tunneling diodes can be operated as a voltage controlled spin-switch. Devices when are constricted to nanometer dimensions show a stronger ferromagnetic behaviour.

Simulation of the p-type RTD

  • Autoři: doc. RNDr. Jan Voves, CSc.,
  • Publikace: The Sixth International Conference on Advanced Semiconductor Devices and Microsystems. Bratislava: Slovak University of Technology, 2006. p. 125-128. ISBN 978-1-4244-0396-7.
  • Rok: 2006

Ultrathin InAs and modulated InGaAs Layers in GaAs grown by MOVPE studied by photomodulated reflectance spectroscopy

Optical Characterization of MOVPE Grown Delta-InAs Layers in GaAs

Quantum Devices Transport Simulation

  • Autoři: Třebický, T., doc. RNDr. Jan Voves, CSc.,
  • Publikace: Proceedings of Workshop 2005. Praha: České vysoké učení technické v Praze, 2005. pp. 396-397. ISBN 80-01-03201-9.
  • Rok: 2005
  • Pracoviště: Katedra mikroelektroniky
  • Anotace:
    Simulation is very important phase in development of semiconductor structures. Main purpose of the procedure of simulation is in testing the functionality of given structure and to determine its significant characteristics. With more sophisticated simulators in terms of the best physical model we can even predict the properties of these structures. It might put aside the manufacturing of non functional devices, so its place in a stage of development is wellearned.

Quantum Devices Transport Simulation Using Transfer Matrix Method

  • Autoři: Třebický, T., doc. RNDr. Jan Voves, CSc., Suchánek, P.
  • Publikace: Modern Methods of Solutions, Designs and Applications of Electronic Devices. Brno: Vysoké učení technické v Brně, 2005. pp. 91-96. ISBN 80-214-3089-3.
  • Rok: 2005
  • Pracoviště: Katedra mikroelektroniky
  • Anotace:
    The paper describes the properties of one dimensional simulator for modeling quantum electronic system with an arbitrary layered semiconductor structure. Actually, the simulator is being used for predicting the significant parameters of newly designed resonant tunneling diodes with structure containing band steps outside the barriers to decrease the interference between the emitter charge of free electrons and charge in the well leading to undesirable current plateau on the I-V diode characteristics.

Trends and Skill Needs in the Field of Nanotechnology - the State of Affaires in the Czech Republic in the European Context

  • Autoři: doc. RNDr. Jan Voves, CSc.,
  • Publikace: International Workshop Emerging Technologies: new skill needs in the field of nanotechnology. Stuttgart: Fraunhofer Institute for Industrial Engineering, 2005. p. 59-129.
  • Rok: 2005
  • Pracoviště: Katedra mikroelektroniky
  • Anotace:
    Trends and skill needs in the field of nanotechnology - the state of affairs in the Czech Republic in the European Context

Ultrathin MOVPE Grown InAs Layers in GaAs Characterized by Photomodulated Reflectance Spectroscopy

Experimental Study of AlGaAS/GAAS Double Barrier Resonant Tunneling Diodes Grown by MBE

  • Autoři: Jackiv, R., doc. RNDr. Jan Voves, CSc.,
  • Publikace: Abstracts of 2nd Ukrainian Scientific Conference on PHYSICS of SEMICONDUCTORS. Chernivtsi: Yuriy Fedkovych Chernivtsi National University, 2004. pp. 191-192. ISBN 966-568-710-7.
  • Rok: 2004

Experimental Study of the I-V Bistabilities of Resonant Tunneling Diodes

  • Autoři: Jackiv, R., Třebický, T., doc. RNDr. Jan Voves, CSc., Výborný, Z., Cukr, M., Jurka, V.
  • Publikace: 24th International Conference on Microelectronics. Piscataway: IEEE, 2004. pp. 359-362. ISBN 0-7803-8166-1.
  • Rok: 2004

Improvements of InGaAs Layer Properties by MOVPE Digital Growth -InAs/GaAs Superlattices for Laser Active Region

  • Autoři: Hospodková, A., Pangrác, J., Hulicius, E., Oswald, J., prof. Ing. Pavel Hazdra, CSc., doc. RNDr. Jan Voves, CSc., Mačkal, A., Pacherová, O., Melichar, K., Šimeček, T.
  • Publikace: The Twelfth International Conference on Metal Organic Vapor Phase Epitaxy - Proceedings post deadline inset. Warrendale: The Minerals, Metals & Materials Society, 2004. pp. ?.
  • Rok: 2004

Optical characterization of MOVPE grown delta-InAs layers in GaAs

  • Autoři: prof. Ing. Pavel Hazdra, CSc., doc. RNDr. Jan Voves, CSc., Hulicius, E., Pangrác, J.
  • Publikace: 7th International Workshop on Expert Evaluation and Control of Compound Semiconductor Materials and Technologies. Montpellier: Université Montpellier II, 2004. pp. 73-74.
  • Rok: 2004

Radiative Recombination Mechanism of Subnanometric InAs/GaAs Laser Structures

Resonant Tunnelig Diodes - Three State Circuits

  • Autoři: Jackiv, R., doc. RNDr. Jan Voves, CSc., Výborný, Z., Cukr, M.
  • Publikace: The 11th Electronic Devices and Systems Conference. Brno: VUT v Brně, 2004. pp. 27-29. ISBN 80-214-2701-9.
  • Rok: 2004

Resonant Tunneling Diodes - Simulation and Experiment

  • Autoři: Jackiv, R., Třebický, T., doc. RNDr. Jan Voves, CSc., Výborný, Z., Cukr, Z.
  • Publikace: Workshop 2004. Praha: České vysoké učení technické v Praze, 2004. pp. 406-407. ISBN 80-01-02945-X.
  • Rok: 2004

Spintronic Applications of Ferromagnetic Nanostructures

  • Autoři: doc. RNDr. Jan Voves, CSc.,
  • Publikace: NENAMAT Mobilization Workshop NANO '04, Book of Abstracts. Brno: VUTIUM Press, 2004. pp. 49. ISBN 80-214-2672-1.
  • Rok: 2004

Bloch oscillations in superlattices: Monte-Carlo analysis using 2D scattering model

InAs delta-layer structures in GaAs grown by MOVPE and characterised by luminescence and photocurrent spectroscopy

Nanotechnologie a počítače

Bloch Oscillation In Superlattices: Monte Carlo Analysis Using 2D Scattering Model

  • Autoři: Čermáková, H., doc. RNDr. Jan Voves, CSc.,
  • Publikace: Proceedings of ICSNN'02. Toulouse: Universite Toulouse III, 2002. pp. 134.
  • Rok: 2002

Characterization of lasers with delta-InAs layers in GaAs

  • Autoři: prof. Ing. Pavel Hazdra, CSc., doc. RNDr. Jan Voves, CSc., Hulicius, E., Oswald, J., Pangrác, J., Melichar, K., Šimeček, T.
  • Publikace: Proceedings of Workshop 2002. Praha: České vysoké učení technické v Praze, 2002. pp. 424-425. ISBN 80-01-02511-X.
  • Rok: 2002

Delta-InAs structures embedded in GaAs grown by MOVPE characterised by electroluminescence and photocurrent spectroscopy

Design and Characterisation of MBE Grown HEMT Structures

Lasers with delta-InAs layers in GaAs

Terahertz Bloch Oscillations in Semiconductor Superlattices

  • Autoři: Čermáková, H., doc. RNDr. Jan Voves, CSc.,
  • Publikace: ASDAM 2002. Bratislava: IEEE, 2002. pp. 133-135. ISBN 0-7803-7276-X.
  • Rok: 2002

InAs/GaAs Lasers for Optical Communication: Preparation and Properties

Lasers with Delta-InAs Layer in GaAs

Aplikace nástrojů TCAD pro návrh nových polovodičových struktur

  • Autoři: doc. RNDr. Jan Voves, CSc.,
  • Publikace: Sborník příspěvků ze semináře Odborné skupiny Polovodiče Fyzikální vědecké sekce Jednoty českých matematiků a fyziků. Praha: Jednota českých matematiků a fyziků, 2000. pp. 41-42. ISBN 80-7015-720-8.
  • Rok: 2000
  • Pracoviště: Katedra mikroelektroniky
  • Anotace:
    Modelování transportních procesů v elektronických součástkách

Information Technology Research

Quantum Size InAs/GaAs Lasers - Preparation and Properties

Electron Transport in Semiconductor Superlattices

  • Autoři: Čermáková, H., doc. RNDr. Jan Voves, CSc.,
  • Publikace: Proceedings of Workshop 99. Praha: České vysoké učení technické v Praze, 1999. pp. 204.
  • Rok: 1999

Photoluminescence from the MOVPE Grown GaAs/GaAlAs Superlattices

  • Autoři: doc. RNDr. Jan Voves, CSc., prof. Ing. Pavel Hazdra, CSc.,
  • Publikace: Proceedings of the 8th European Workshop on Metal-Organic Vapour Phase Epitaxy and Related Growth Techniques EW MOVPE VIII. Praha: AV ČR, Fyzikální ústav, 1999. pp. 385-388. ISBN 80-238-3551-3.
  • Rok: 1999

Simulation of Bloch Oscillations in Superlattices

  • Autoři: Čermáková, H., doc. RNDr. Jan Voves, CSc.,
  • Publikace: Workshop 98. Praha: České vysoké učení technické v Praze, 1998. pp. 313-314.
  • Rok: 1998

Bloch Oscillations in Superlattice Simulated by Monte Carlo Method

  • Autoři: doc. RNDr. Jan Voves, CSc., Čermáková, H.
  • Publikace: Proceedings of 21st International Conference on Microelectronics. Piscataway: IEEE, 1997. pp. 129-132. ISBN 0-7803-3664-X.
  • Rok: 1997

Photoluminescence in the GaAs/GaAlAs Superlattices Proposed for Bloch Oscillations

Study of Heterojunction Structures at Low Temperatures

  • Autoři: Sichrovský, P., Tayari, J., doc. RNDr. Jan Voves, CSc.,
  • Publikace: Workshop 97. Praha: České vysoké učení technické v Praze, 1997. pp. 1037-1038.
  • Rok: 1997

Simulace Blochových oscilací v polovodičové supermřížce

  • Autoři: doc. RNDr. Jan Voves, CSc.,
  • Publikace: Sborník abstraktů - 12. konference českých a slovenských fyziků. Ostrava: VŠB-TUO, 1996. pp. 137.
  • Rok: 1996

2-D Simulation of Ion Irradiated Silicon Power Devices

Elektronické součástky nové generace

Vertical Electron Transport in Infinite Superlattice Monte Carlo Simulation

  • Autoři: doc. RNDr. Jan Voves, CSc.,
  • Publikace: Workshop 95. Praha: České vysoké učení technické v Praze, 1995. pp. 89-90.
  • Rok: 1995

Vertical Electron Transport in Semiconductor Superlattices Monte Carlo Simulation

  • Autoři: doc. RNDr. Jan Voves, CSc.,
  • Publikace: Materials Science and Engineering A - Structural Materials: Properties, Microstructure and Processing. 1995, B35(12), 417-420. ISSN 0921-5093.
  • Rok: 1995

Vertical Transport in Short-Period Superlattices - Simulation by the Monte Carlo Method

Accurate Simulation of Combined Electron and Ion Irradiated Silicon Devices for Local Lifetime Tailoring

  • Pracoviště: Katedra mikroelektroniky
  • Anotace:
    Hydrogen, helium and electron irradiation of power diodes - measurements and simulation

Big Hopes for Application of Radiation Damages in Semiconductor Devices

Inversion Layer Quantization in Monte Carlo MOSFET Simulation

  • Autoři: doc. RNDr. Jan Voves, CSc.,
  • Publikace: Europhysics Conference Abstracts. 17 A. Regensburg: European Physical Society and Deutsche Physikalische Gesellschaft, 1993, pp. 1471.
  • Rok: 1993

Monte Carlo Mosfet Modelling Including Quantum Effects

  • Autoři: doc. RNDr. Jan Voves, CSc.,
  • Publikace: Workshop 93. Praha: České vysoké učení technické v Praze, 1993. pp. 41-42.
  • Rok: 1993

Monte Carlo MOSFET Simulator Including Inversion Layer Quantization

  • Autoři: doc. RNDr. Jan Voves, CSc.,
  • Publikace: Simulation of Semiconductor Devices and Processes. Wien: Springer, 1993. pp. 185-188. ISBN 3-211-82504-5.
  • Rok: 1993

TCAD - A Progressive Tool for Engineers

Radiateive Recombination Mechanism of Subnanometric InAs/GaAs Laser Structures

Za stránku zodpovídá: Ing. Mgr. Radovan Suk