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Characterization of hydrogenated silicon thin films and diode structures with integrated silicon and germanium nanoparticles
Stuchlík, Jiří ; Fajgar, R. ; Remeš, Zdeněk ; Kupčík, Jaroslav ; Stuchlíková, Hana
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.
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Germanium and tin nanoparticles encapsulated in amorphous silicon matrix for optoelectronic application
Stuchlíková, The-Ha ; Remeš, Zdeněk ; Stuchlík, Jiří
The plasma enhanced chemical vapour deposition was combined with in situ deposition of Ge and Sn thin film by evaporation technique at surface temperature about 220 °C to form nanoparticles on the surface of hydrogenated silicon thin films to prepare diodes. Formation of nanoparticles was additionally stimulated by plasma treatment through a low pressure hydrogen glow discharge. The diodes based on PIN diode structures with and without the embedded Ge or Sn nanoparticles were characterized by temperature dependence of electrical conductivity, activation energy of conductivity, measurement of volt-ampere characteristics in dark and under solar illumination\n
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The photoluminescence and optical absorptance of plasma hydrogenated nanocrystalline ZnO thin films
Remeš, Zdeněk ; Chang, Yu-Ying ; Stuchlík, Jiří ; Mičová, J.
We have developed the technology of the deposition of the nominally undoped ZnO nanocrystalline thin films by DC reactive magnetron sputtering of Zn target in the gas mixture of argon and oxygen plasma. We have optimized the photoluminescence spectroscopy for measuring optically scattering thin layers with the high sensitivity, precise sample positioning and very low influence of the scattered excitation light. Here we present the latest results on the enhancement of the photoluminescence of the nanocrystalline ZnO thin films after plasma hydrogenation. The photoluminescence in near UV region has been enhanced whereas the deep defect related photoluminescence has been significantly decreased. We found good room temperature stability of the plasma hydrogenated ZnO nanocrystals in air, but fast degradation at elevated temperature\n
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Electronic transfer between nanostructures. Negative differential resistance in conductive polymers.
Král, Karel ; Menšík, Miroslav
The effect of negative differential resistance can be observed experimentally in some material systems based on polymers. These observation are explained usually to be due to the presence of certain carrier traps which can capture the carriers of the electric current. In the present theoretical work we are going to show that besides this carrier trapping origin of the negative differential resistance there can also be an intrinsic mechanism present, causing such an effect. Namely, instead of the traps, the electron-phonon interaction can cooperate with the tunneling of the charge carriers between their localized states and can provide the effect the negative differential resistance. This electron-phonon interaction is included in a non-perturbative way. The theory will be briefly summarized and explained.
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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.
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The hydrogen plasma doping of ZnO thin films and nanoparticles
Remeš, Zdeněk ; Neykova, Neda ; Potocký, Štěpán ; Chang, Yu-Ying ; Hsu, H.S.
The optical absorptance and photoluminescence studies has been applied on the hydrogen and oxygen plasma treated, nominally undoped ZnO thin films and aligned nanocolumns grown on the nucleated glass substrate by the hydrothermal process in an oil bath containing a flask with ZnO nutrient solution. The localized defect states at 2.3 eV below the optical absorption edge were detected by photothermal deflection spectroscopy (PDS) in a broad spectral range from near UV to near IR. The optical absorptance spectroscopy shows that hydrogen doping increases free electron concentration changing ZnO to be electrically conductive (hydrogen doping).\n
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