Ing. Eva Horynová

Molybdenum oxide is an intensively studied material, thanks to its high bandgap, high work function, and potentially also photochromism, plasmonic properties, and layered structure. In this contribution, we employ Pulsed Laser Deposition (PLD) from stoichiometric MoO3 and metal Mo target at temperature range of 25 °C – 500 °C and oxygen pressure variation of 0.1 mbar – 0.4 mbar to deposit high transparency MoO3 layers. The combination of Photothermal Manuscript File Click here to view linked ReferencesDeflection Spectroscopy (PDS) and Spectral Ellipsometry is applied to accurately track all the optical properties. The X-ray diffraction and Scanning Electron Microscopy (SEM) are used to monitor crystallinity and surface morphology.

Transition metal oxides are materials combining properties of electrical conductivity, optical transparency, and catalytical function. They are widely used in applications including solar cells, flat panel displays, and detectors. In particular, high work function oxides such as MoO3, WO3, and V2O5 have become popular. In many applications, low deposition temperatures are required, leading to amorphous structure. In this study, thin films of amorphous MoOX, WOX, and VOX were prepared by pulsed laser deposition, and their optical properties and work function were determined. Samples of polycrystalline ZnO were also prepared for comparison. Substrate temperature was varied in the range of 25 °C–100 °C and oxygen pressure was varied in the range of 10–20 Pa during the process. Effect of pressure during sample cool-down and chamber venting was also observed.. Optical characterization was based on photothermal deflection spectroscopy, which is a non-contact and non-destructive method for measuring directly absorptance spectra with sensitivity down to 10–4. Absorptance in the band gap serves as an indication of the presence of defects such as oxygen vacancies or metallic phases. Our optimized films achieved a sub-bandgap absorption coefficient as low as 103 cm−1 for MoOX, VOX, and 102 cm−1 in the case of the WOX. From the gradient of the absorption edge, Urbach energy was obtained, evaluating disorder in the semiconductor material. The work function of each material was obtained by Kelvin probe, and a slight correlation with Urbach energy was found. X-ray photoelectron spectroscopy indicated successful stochiometric transfer mainly for the lowest pressure and highest temperature samples.

Thin film layers are used in a wide range of fields (microchips, solar cells, etc.)because of the high dependency of their properties on the thickness of the layer. It is important to know how to achieve different thickness and quality of the layers by changing conditions of deposition. Samples of oxide thin film layers were prepared by magnetron sputtering. Two different materials were used - aluminum oxide and zinc oxide. Effect of different conditions (time and power of plasma)during the deposition was observed. The samples were evaluated from a few different points of view. Firstly, the thickness and capacity of each layer were measured. Thickness was also calculated from capacity and then compared to measured values. As expected, thickness increased with increasing time of deposition and with the increasing power of plasma during the deposition. Detail images of the layers were captured by an optical microscope and these images were processed in order to measure grain size. Average grain size was increasing with higher power during the deposition.

Fused Deposition Modelling (FDM) is one of the most common methods of 3D printing used in many fields of industry, especially in development departments. Since plastics are fundamental materials for electronics industry, the aim of this work is to examine dielectric properties of objects printed from such materials. This work’s contribution is the evaluation of the dependency of the printed objects properties on printing quality and the use of 3D printed plastic components in electronics. For the experiment, three commonly used materials in FDM were chosen – PLA, ABS and PET-G. The materials were pure without any additional admixtures and the relevant test samples were printed with different printing resolution (height of one layer). The following properties were examined – permittivity, dissipation factor and dielectric strength. The results showed that permittivity slightly decreased with increasing height of one layer. Dissipation factor varied significantly in the measured range and there was no apparent dependency on the printing resolution. Rather, it was an indicator of the printing quality. Dielectric strength also slightly decreased with the decreasing resolution; however this parameter was governed primarily by the employed material. Generally, an improvement of the dielectric properties of these materials is required due to a relatively small dielectric strength, for example by adding admixtures to the base material or better printing quality.

Purpose – The purpose of this paper is to increase the reliability of manufactured electronics and to reveal reliability significant factors. The experiments were focused especially on the influence of the reflow oven parameters presented by a heating factor. Design/methodology/approach – The shear strength of the surface mount device (SMD) resistors and their joint resistance were analyzed. The resistors were assembled with two Sn/Ag/Cu-based and one Bi-based solder pastes, and the analysis was done for several values of the heating factor and before and after isothermal aging. The measurement of thickness of intermetallic compounds was conducted on the micro-sections of the solder joints. Findings – The shear strength of solder joints based on the Sn/Ag/Cu-based solder alloy started to decline after the heating factor reached the value of 500 s · K, whereas the shear strength of the solder alloy based on the Bi alloy (in the measured range) always increased with an increase in the heating factor. Also, the Bi-based solder joints showed shear strength increase after isothermal aging in contrast to Sn/Ag/Cu-based solder joints, which showed shear strength decrease. Originality/value – The interpretation of the results of such a comprehensive measurement leads to a better understanding of the mutual relation between reliability and other technological parameters such as solder alloy type, surface finish and parameters of the soldering process.

3D printing is an additive manufacturing process for building three-dimensional solid objects. This technology has use in many fields of industry, especially in rapid-prototyping. This project is focused on possibilities of use of 3D printing in electronics industry. 3D printed objects were investigated with a view to their electrical properties. The comparison of these properties for various common materials (PLA and ABS) was examined. The results showed that some of the properties of PLA are promising (relatively high dielectric strength, volume resistivity) compared to others (dielectric constant, loss tangent) that are not optimal for use in electronics industry and requires some improvements in form of additives. ABS has higher loss tangent than PLA, no significant difference in dielectric constant was found between ABS and PLA. Generally, an improvement of the electrical properties of these materials is required, for example by adding some additives to the base material.