Národní úložiště šedé literatury Nalezeno 9 záznamů.  Hledání trvalo 0.01 vteřin. 
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
Relation between optical and microscopic properties of hydrogenated silicon thin films with integrated germanium and tin nanoparticles
Stuchlík, Jiří ; Stuchlíková, The-Ha ; Čermák, Jan ; Kupčík, Jaroslav ; Fajgar, Radek ; Remeš, Zdeněk
The hydrogenated amorphous silicon layers (a-Si:H) were deposited by PECVD method on quartz substrates. During interruption of PECVD process the vacuum chamber was pumped up to 10-5 Pa and 1 nm thin films of Germanium or Tin were evaporated on the surface. The materials form isolated nanoparticles (NPs) on the a-Si:H surface. Then the deposited NPs were covered and stabilized by a-Si:H layer by PECVD. Those two deposition processes were alternated 5 times. The a-Si:H thin films with integrated Ge or Sn NPs were characterized optically by PDS and CPM methods, and microscopically by SEM and AFM microscopies. Optical and microscopic properties of the structures are correlated and discussed considering their application in photovoltaics.\n
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
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.
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
Preparation of zinc oxide nanorods colloid from thin layers
Mičová, Júlia ; Remeš, Zdeněk ; Chang, Yu-Ying ; Neykova, Neda
The interest in ZnO (zinc oxide) nanoparticles is increasing due to low cost of their processing as well as the ability of fabricating ZnO nanostructures with controllable morphology such as size, shape and orientation. Our choice of method of the preparation of the nanostructured thin ZnO layers is the hydrothermal growth of ZnO nanorods on glass substrates coated by the nucleation layer deposited by the reactive magnetron sputtering. We have developed and optimized conditions of the thin layer growth with controllable dimensions of nanorods followed by the ultrasound peeling. The colloid of ZnO nanorods was characterized by measuring the size of particles using the dynamic light scattering (DLS) and the scanning electron microscopy (SEM). We found that the dynamic light scattering (DLS) can’t be directly used for size evaluation of ZnO nanorods due to their non- sperical shape. \n
Hydrogen plasma treatment of ZnO thin films
Chang, Yu-Ying ; Neykova, Neda ; Stuchlík, Jiří ; Purkrt, Adam ; Remeš, Zdeněk
ZnO is an attractive wide band gap semiconductor with large exciton binding energy, high refractive index, high biocompatibility and diversety of nanostructure shapes which makes it suitable for many applications in the optoelectronic devices, optical sensors, and biosensors. We study the effect of hydrogen plasma treatment of the nominally undoped ZnO thin film deposited by DC reactive magnetron sputtering of Zn target in the gas mixture of argon and oxygen plasma. The SEM images show that the crystal size increases with film thickness. We confirm, that the electrical conductivity significantly increases after hydrogen plasma treatment by 4 orders of magnitude. Moreover, the increase of the infrared optical absorption, related to free carrier concentration, was detected below the optical absorption edge by the photothermal deflection spectroscopy.\n
The intrinsic submicron ZnO thin films prepared by reactive magnetron sputtering
Remeš, Zdeněk ; Stuchlík, Jiří ; Purkrt, Adam ; Chang, Yu-Ying ; Jirásek, Vít ; Štenclová, Pavla ; Prajzler, V. ; Nekvindová, P.
The DC reactive magnetron sputtering of metallic target in oxide atmosphere is a simple method of depositing the intrinsic (undoped) nanocrystalline layers of metal oxides. We have optimized the deposition of the intrinsic ZnO thin films with submicron thickness 50-500 nm on fused silica glass substrates and investigated the localized defect states below the optical absorption edge down to 0.01 % using photothermal deflection spectroscopy from UV to IR. We have shown that the defect density, the optical absorptance and the related optical attenuation in planar waveguides can be significantly reduced by annealing in air at 400 °C.
Transfer of electrons or holes between localized states. Application to polymer electric conductivity
Král, Karel ; Menšík, Miroslav
Basing on the quantum transport formalizm a formula for the irreversible transfer of charged particles has been introduced by us recently. This formula is expected to be suitable for the theoretical description of the electron or hole transfer between quantum dots, other nanoparticles, molecules, and so on. We discuss shortly the main physical properties of the formula. We also demonstrate the use of the formula for the theoretical analysis of the electronic physical properties of some electrically conductive polymers.\n

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