Jan M. Olchowik

The preparation and properties of ''porous silicon-nickel ferrite'' nanoheterocomposites for gas detectors

This paper discusses the preparation and properties of gas detectors based on “porous silicon–nickel ferrite” nanocomposites. Impedance spectroscopy was used to measure sensitivity to ethanol and isopropanol vapours in the presence of an alternating electric field. The results were interpreted with the help of an equivalent electrical circuit. In the analysis of the resistive–capacitive properties in the equivalent circuit a constant phase element was used.

Effect of interface energy on erosion of AIIIBV substrates during liquid phase heteroepitaxy

Abstract Erosive damage to the solid phase surface is the frequently observed effect of the exposure of the multicomponent liquid solution of A III B V compounds to A III B V binary substrates. This erosion particularly affects heterocompositions with a high lattice parameter mismatch. The mechanisms leading to such a phenomenon were analyzed for the case of the Ga–In–P–As/InP and Ga–In–P–As/GaAs heteropairs. Based on the model of interatomic interactions at the interface, it was found that the erosion instability of the interface depends mainly on the excessive energy of the lattice in this region.

Growth and characterization of PrBa2Cu3O7-δ single crystals

Abstract We report on the growth of PrBa 2 Cu 3 O 7-δ single crystals in the Al 2 O 3 and ZrO 2 crucibles by flux method. The high influence of the reaction between crucible and liquid on the initial melt composition has been established. We found that the precipitation of the chemically stable compound BaZrO 3 and BaAl 2 O 4 occurs by direct chemical reaction between BaCuO 2 and ZrO 2 or Al 2 O 3 crucibles materials. Free separated crystals with maximum size of 3 x 5 x 0.1 mm 3 have been obtained. PrBa 2 Cu 3 O 7-δ crystals exhibit a typically semiconducting behaviour. The resistivity depends on the thermal treatment and decreases by about two orders of magnitude for oxygen concentration between 6.65 to 6.95.

Structural properties of superconducting PrBa2Cu3O7−δ single crystals

Abstract The influence of high-temperature reduction/oxidation treatment on the structural properties of superconducting PrBa 2 Cu 3 O 7−δ (PrBCO) single crystals was examined. The scanning electron microscopy (SEM) analysis has shown that even the short-lasting exposure to the oxygen-deficient atmosphere leads to creation of regular-shaped crystallites of PrBaO 3 and BaCuO 2 phases with the size of 0.5 ÷ 2.0 μ m on the smooth and flat crystal surface. The energy dispersive x-ray (EDX) investigations performed on the cross-sections of the superconducting crystals have indicated that the post-growth thermal treatment reduces the amount of Pr on the Ba-sites. Our results strongly support all the concepts attributing the suppression of superconductivity in this system to the excess of Pr in the crystal structure of samples synthesised by the standard methods.

Finite element method simulation of interface evolution during epitaxial growth

Epitaxial Lateral Overgrowth (ELO) is a method of epitaxial growth on a partially masked substrate. It can be a promising method for photovoltaic applications due to a possibility of producing thin and high quality silicon substrates. Since the mask prevents propagation of the substrate dislocations to the laterally overgrown parts of the ELO layer they are characterized by a lower dislocation density than the substrate. It means that it is possible to fabricate good quality solar cells on a poor quality Si substrate. The main goal of the research is to obtain a higher growth rate in the lateral direction than in the direction normal to the substrate. The epilayer growth kinetics depends on many technological factors, basically the growth temperature, the cooling rate, the solvent and the mask filling factor. For this reason the best way to achieve the goal is a computational analysis of the epitaxial layer growth process. This work presents a two-dimensional computational study of such a process of growth for different technological conditions. The computational model is based on the assumption of pure diffusion control growth.

Progress of development of PV systems in south-eastern Poland

European project IEE under acronym “PVs in Bloom”, which we are participant, aims in elaboration a strategy of development photovoltaics on marginal areas of EU. Optimal areas can be chosen from a variety of marginal terrains like waste dumps, every kind of buffer zones etc., which can be easily adapted to build photovoltaic power plants (PVPPs). In this analysis, we present the action of our team as well as local governments and business in investing in the PVPPs construction in Lublin region.

Study of generation of GaxIn1−xPyAs1−y transition layers obtained by liquid phase epitaxy

Abstract The feasibility of fabrication of the so-called GaxIn1−xPyAs1−y transition layers on the GaAs substrate by liquid phase epitaxy is demonstrated. It is shown that the most favorable substrate to fabricate good quality (GaxIn1−xPyAs1−y)1 transition layers is GaAs〈111〉A, which is stable for a wide range of compositions. It is also shown that the formation of thin graded optical windows of GaxIn1−xPyAs1−y compounds on the GaAs〈111〉A surface may be realized in a reproducible manner for very short-time exposures.

Influence of dielectric coverage on photovoltaic conversion of silicon solar cells obtained by epitaxial lateral overgrowth

This work presents an analysis of the influence of SiO2 dielectric coverage of a Si substrate on the solar-cell efficiency of Si thin layers obtained by epitaxial lateral overgrowth (ELO). The layers were obtained by liquid phase epitaxy (LPE). All experiments were carried out under the following conditions: initial temperature of growth: 1193 K; temperature difference ΔT = 60 K; ambient gas: Ar; metallic solvent: Sn+Al; cooling rates: 0.5 K/min and 1 K/min. To compare the influence of the interior reflectivity of photons, we used two types of dielectric masks in a shape of a grid etched in SiO2 along the 〈110〉 and 〈112〉 directions on a p+ boron-doped (111) silicon substrate, where silicon dioxide covered 70 % and 80 % of the silicon surface, respectively. The results obtained in this work depict the correlation between the interior efficiency and percentage of SiO2 coverage of the substrate of the ELO solar cells.

Analisis of internal reflectivity of silicon ELO PV cells obtained by LPE

This work contains analysis of a SiO2 dielectric geometry influence on a epitaxial lateral overgrowth (ELO) thin films and solar photo-conversion efficiency. Layers used in the experiment were obtained in LPE (Liquid Phase Epitaxy) process in the same thermodynamical conditions: starting temperature of growth: 1193K, temperature difference ΔT=60K, ambient gas: Ar, metallic solvent: Sn+Al and in a different cooling rates: 0,25K/min and 0,75K/min. Also we used various dielectric masks with a different geometry: grid opened in SiO2 layer along <110> and <112> directions on a p+ boron doped (111) silicon substrate, where silicon dioxide covers from 70% up to 90% of the silicon surface. Results of the analyzes show correlation between efficiency and percentage of SiO2 coverage and velocity of crystallization on obtained solar cells.

Silicon-On-Insulator Thin Films Grown by Liquid Phase Epitaxy

Crystalline silicon has the advantage of being one of the most abundant elements in nature, but still about the half the cost of a finished module is due to the material itself, and it needs to be reduced [1]. During recent years, scientists attention has been focused on thin film materials technologies, as they seem to be promising alternatives to bulk silicon materials, reducing the cost of PV module production. Due to this fact, an increased activity has taken place using liquid phase epitaxy (LPE), in particular epitaxial lateral overgrowth (ELO), to prepare silicon thin film materials for solar cells applications [2, 3].