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Pulsed Laser Deposition under Low Background Gas Pressure.
Koštejn, Martin ; Fajgar, Radek ; Dřínek, Vladislav ; Jandová, Věra ; Klementová, Mariana ; Bakardjieva, Snejana
The nucleation of nanoparticles was applied during gold deposition onto TiO2 layers. For nucleation, up to 10 Pa of inert gas (argon) was used. Argon molecules efficiently helped to cool temperature of evolving plume and initiated the nucleation which resulted in deposition of gold nanoislands. Gold nanoparticles incorporated in TiO2 layers provided plasmonic properties. Au/TiO2 layers were used for water splitting as proved by photoelectrochemical measurements.
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Characterization of hydrogenated silicon thin films and diode structures with integrated germanium nanoparticles
Stuchlík, J. ; Fajgar, R. ; Remeš, Z. ; Kupčík, Jaroslav ; Stuchlíková, H.
P-I-N diode structures based on the thin films of amorphous hydrogenated silicon (a-Si: H) deposited by Plasma Enhanced Chemical Vapor Deposition (PECVD) technique were prepared with embedded Si and Ge nanoparticles. The Reactive Laser Ablation (RLA) of germanium target was used to cover the intrinsic a-Si: H layer by Ge NPs under a low pressure of the silane. The RLA was performed using focused excimer ArF laser beam under SiH4 background atmosphere. Reaction between ablated Ge NPs and SiH4 led to formation of Ge NPs covered by thin GeSi: H layer. The deposited NPs were covered and stabilized by a-Si: H layer by PECVD. Those two deposition processes were alternated repeatedly. Volt-ampere characteristics of final diode structures were measured in dark and under illumination as well as their electroluminescence spectra.
Recovery of Waste Semiconductors for CVD Precursors.
Bumba, Jakub ; Dytrych, Pavel ; Fajgar, Radek ; Dřínek, Vladislav
The newly patented method for regeneration of ultrapure silicon and germanium via magnesium silicide and magnesium germanide from waste photovoltaic (PV) cells, broken germanium lenses and waste magnesium chips was utilized to obtain chemical vapour deposition (CVD) precursors for application in electronics, optics or nanoparticles synthesis. Magnesium silicide and germanide were prepared directly by thermal synthesis from waste materials in optimized tube reactor at 400°C and 5 Pa. X-Ray Diffraction (XRD) confirmed 97.9% respective 95% purity of products. The presence of silicon and germanium hydrides (CVD precursors) prepared by acid hydrolysis in the second step of the process was verified by Gas Chromatography–Mass Spectroscopy (GC/MS) and Fourier Transform Infrared Spectroscopy (FTIR). The crude, unrefined mixture of silicon hydrides served as raw material for CVD experiment at different substrates. SEM images confirmed occurrence of various micro and nano particles which could be used in electronics, optics and catalysis.
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Characterization of hydrogenated silicon thin films and diode structures with integrated germanium nanoparticles
Stuchlík, Jiří ; Fajgar, Radek ; Kupčík, Jaroslav ; Remeš, Zdeněk ; Stuchlíková, The-Ha
Substrates with ZnO (or ITO) conductive layers were covered by thin film of a-Si:H deposited by PECVD technique. Under a turbo-molecular vacuum (10-4 Pa) the reactive laser ablation (RLA) was used to cover this a-Si:H thin film by germanium NPs. The RLA was performed using focused excimer ArF laser beam (193 nm, 100 mJ/pulse) under SiH4 background atmosphere (0.5 Pa). As a target the elemental germanium was used. Reaction between ablated Ge and silane led to formation of Ge NPs covered by thin SiGe layer. Then the deposited NPs were covered and stabilized by a-Si:H layer by PECVD. Those two deposition processes was alternated and applied a few times. The Si:H thin films with integrated Ge NPs were characterized by microscopic, spectroscopic and diffraction techniques. I-V characteristics of final diode structures without and under illumination were measured as well as their electroluminescence behaviour.
The deposition of amorphous and amorphous hydrogenated silicon with embedded cubic Mg.sub.2./sub.Si nanoparticles
Stuchlíková, The-Ha ; Stuchlík, Jiří ; Remeš, Zdeněk ; Fajgar, Radek ; Galkin, N.G. ; Galkin, K.N. ; Chernev, I.M.
We study possibilities how to increase a by usage of magnesium silicide nanoparticles (Mg2Si-NPs) in structure of Si: H. In this paper we introduce two technics -combination of PECVD and Vacuum Evaporation (VE) and Reactive Laser Ablation (RLA) -for preparation of cubic structure of Mg2Si-NPs in amorphous (a-Si) or amorphous hydrogenated (a-Si: H) silicon matrix. Formation of Mg2Si-NPs was proved by Raman spectroscopy. Likewise we introduce optical changes measured at absorption edge and the first results on realized NIP structures.
The deposition of germanium nanoparticles on hydrogenated amorphous silicon.
Stuchlík, J. ; Volodin, V.A. ; Shklyaev, A.A. ; Stuchlikova, T.H. ; Ledinsky, M. ; Čermák, J. ; Kupčík, Jaroslav ; Fajgar, R. ; Mortet, V. ; More-Chevalier, J. ; Ashcheulov, P. ; Purkrt, A. ; Remeš, Z.
We reveal the mechanism of Ge nanoparticles (NPs) formation on the surface of the hydrogenated amorphous silicon (a-Si:H) deposited by Plasma Enhanced Chemical Vapor Deposition (PECVD) on ITO and a on boron doped nanocrystalline diamond (BDD). The coating of Ge NPs on a-Si:H was performed by molecular beam epitaxy (MBE) at temperatures up to 450 degrees C. The Ge NPs were characterized by Raman spectroscopy, scanning electron microscopy (SEM) and high resolution transmission electron microscopy (HRTEM). The nanocrystalline Ge particles are conglomerates of nanocrystals of size 10-15 nm and quantum dots (QDs) with size below 2 nm embedded in amorphous Ge phase. After coating with Ge NPs the a-Si:H thin films show better adhesion on BDD substrates then on ITO substrates.
The deposition of germanium nanoparticles on hydrogenated amorphous silicon
Stuchlík, Jiří ; Volodin, V.A. ; Shklyaev, A.A. ; Stuchlíková, The-Ha ; Ledinský, Martin ; Čermák, Jan ; Kupčík, Jaroslav ; Fajgar, Radek ; Mortet, Vincent ; More Chevalier, Joris ; Ashcheulov, Petr ; Purkrt, Adam ; Remeš, Zdeněk
We reveal the mechanism of Ge nanoparticles (NPs) formation on the surface of the hydrogenated amorphous silicon (a-Si:H) deposited by Plasma Enhanced Chemical Vapor Deposition (PECVD) on ITO and a on boron doped nanocrystalline diamond (BDD). The coating of Ge NPs on a-Si:H was performed by molecular beam epitaxy (MBE) at temperatures up to 450 °C. The Ge NPs were characterized by Raman spectroscopy, scanning electron microscopy (SEM) and high resolution transmission electron microscopy (HRTEM). The nanocrystalline Ge particles are conglomerates of nanocrystals of size 10-15 nm and quantum dots (QDs) with size below 2 nm embedded in amorphous Ge phase. After coating with Ge NPs the a-Si:H thin films show better adhesion on BDD substrates then on ITO substrates.
Preparation of Magnesium Silicide from Recycled Materials for Energy Storage.
Bumba, Jakub ; Dytrych, Pavel ; Šolcová, Olga ; Koštejn, Martin ; Fajgar, Radek ; Maléterová, Ywetta ; Kaštánek, František
Recycling technologies help to save energy, materials and environment. This is the main reason of their popularity. The recovery of semiconductors and metals depends on recycling treatment. A new multi-step technology, which enables to obtain pure silicon and hydrogen from waste materials,is reported in this study. The only by-product is magnesium phosphate, which is a desired fertilizer. Magnesium silicide was successfully prepared from milled silicon photovoltaic (PV) panels and milled Mg obtained from the scrap. The formed magnesium silicide was then hydrolysed by phosphoric acid to form a mixture of silanes. Gaseous products (silanes) were separated by cooling below their boiling temperature by liquid nitrogen and then thermally decomposed by a hot wire, e.g. Pt.This treatment leads to pure silicon and hydrogen release. In this study a deep-in characterization by various methods spectroscopy, Scanning Electron Microscopy (SEM) with Energy Dispersive X- Ray spectroscopy (EDX), etc.) of prepared samples was also done to explain the individual influences, e.g. reaction temperature and atmosphere.
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2 Fajgar, Radek