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LAYERS OF METALS NANOPARTICLES ON VARIOUS SEMICONDUCTORS FOR HYDROGEN DETECTION
Černohorský, Ondřej ; Žďánský, Karel ; Yatskiv, Roman ; Grym, Jan
Metal nanoparticles have many interesting properties which is given by their space restriction. Their large active surface is very well exploited during catalysis. Pd and Pt are metals know for their ability to dissociate molecular hydrogen on single atoms. We prepared Schottky diodes on semiconductors InP, GaN, GaAs, and InGaAs to obtain hydrogen sensor. Method of preparation such diodes is electrophoretic deposition of Pd or Pt nanoparticles from their colloid solution onto semiconductor substrate. Over the layer of nanoparticles, porous metal contact was prepared. Hydrogen molecules are dissociated on these metal nanoparticles and single atom which settles on the interface between metal and semiconductor and they increase or decrease Schottky barrier height. By this method we can measure from 1 ppm H2 in the air, where the current change is over one order of magnitude
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GROWTH OF InP CRYSTALS WITH RARE-EARTH ELEMENTS
Yatskiv, Roman ; Grym, Jan ; Žďánský, Karel ; Pekárek, Ladislav ; Zavadil, Jiří
We report on the influence of rare earth (RE) elements (Pr, Er, and Dy) addition during vertical Bridgman low pressure synthesis on the properties of InP crystals. The temperature dependent Hall measurement and low temperature photoluminescence (PL) spectroscopy were employed to study the changes in electrical and optical properties of the crystals. The observed changes are attributed to the gettering effect of REs caused by the high affinity of REs towards shallow impurities in InP.
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LPE Growth of III-V Semiconductors from rare-earth Treated Melts
Grym, Jan ; Procházková, Olga ; Zavadil, Jiří ; Žďánský, Karel
We focus on the characterization of InP and InGaAsP layers prepared by liquid phase epitaxy with rare-earth admixtures. We applied photoluminescence spectroscopy (PL), capacitance-voltage measurements, and secondary ion mass spectroscopy in order to explain: (i) the gettering effect and conductivity crossover of InP layers for Pr treated samples, (ii) narrowing of the PL and elecroluminescent spectra of the active InGaAsP region of a double-heterostructure LED.
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Růst InP metodou LPE s přídavkem prvků vzácných zemin do taveniny
Grym, Jan ; Procházková, Olga ; Zavadil, Jiří ; Žďánský, Karel
Addition of REs to the growth melt is known to have purifying effect on AIIIBV LPE layers. Each member of REs family acts in its own way. Small addition of Tb, Dy, Tm, and Pr leads to pronounced gettering of shallow donors, the high purity n-type InP can be grown. Exceeding certain concentration, reversal of conductivity type from n to p occurs. Addition of Tm during growth on InP:Fe substrates always results in the preparation of semi-insulating layers due to Fe out-diffusion mediated by RE admixture.
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Physical properties of InP epitaxial layers prepared with dysprosium admixture
Grym, Jan ; Procházková, Olga
Physical properties of commonly prepared InP layers grown by LPE technique and those grown from Dy treated melt are compared. The layers were examined by SEM, low temperature PL spectroscopy, C-V measurements and temperature dependent Hall effect. Structural, electrical and optical properties of InP layers exhibit a significant dependence on the presence of Dy and its concentration in the melt. When increasing the concentration of Dy the reversal of electrical conductivity occurs.
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