The dc conductivity and thermoelectric power of a-Se_{80-x}Ga_{20}Te_{x} (x=0,5,10,15 and 20) thin films were reported in the present work. The free charge carrier concentration was calculated with the help of dc conductivity and thermoelectric power measurements. The calculated values of free charge carrier concentration were used to evaluate the free charge carrier mobility from which grain boundary potential was evaluated. The results are interpreted in terms of small polaron hopping, the structure of Se-Te and the grain boundary potential barrier.
The subjects of investigation are thin semiconductor SnO_{x} films received by thermal oxidation. The influence of gas environments on electrical conductivity of films were investigated by a static way by measurement of kinetic and equilibrium isotherm of adsorption of trimethylamine, alcohol, hydrogen sulfide and ammonia. The communication between a type isotherm of adsorption, chemical nature of gas and temperature is shown.
Thin films of Ge_{100-x}S_x with different values of x are deposited on quartz substrates by a conventional thermal evaporation technique. The electrical conductivity of these films was measured. The experiments reveal that the electronic conduction is strongly composition dependent and is thermally activated with a single activation energy for x>40. A variable range hopping conduction mechanism seems to dominate when x=16 and 27. The optical absorption of the films is investigated using spectrophotometric measurements of the transmittance and reflectance in the wavelength range 200-3000 nm. All the studied compositions obey the Tauc relation concerning the non-direct transitions. The optical energy gap E_g value increases with the increase in chalcogen content x. The Urbach parameter E_0 decreases from 310 meV to 149 meV as x increases from 16 to 70.
Nanofluids are suspensions of nanometrical size particles in a liquid base, which is usually water, oil or ethylene glycol. The potential practical use of nanofluids caused in recent years a considerable intensification of research into their properties. The most widely studied of physical properties include the fluid rheology, thermal conductivity and electrical parameters. The paper presents electrical properties of aluminium oxide (Al₂O₃) nanofluids based on ethylene glycol (EG). Nanoparticles used to produce nanosuspensions employed in measurements have size between 100-300 nm. Electrical properties was investigated in a wide range of temperatures (-10°C-55°C) and frequencies (0.02-200 kHz) using a measuring LCR bridge connected to a temperature stabilization system based on liquid nitrogen and Peltier element.
A solar cell (indium tin oxide (ITO)/p-doped amorphous silicon (p-a-Si:H)/intrinsic polymorphous silicon (i-pm-Si:H)/n-doped crystalline silicon (n-c-Si)) simulation, focused on p-layer doping density NA and surface band bending E_{sbb} at the interface ITO/p-layer has been performed. Despite the deterioration of p-layer material quality with doping density, the reduced bulk recombination was found to compensate for the increased loss in the p-layer. An increase of p-layer doping density NA and contact barrier height φ_{b0} (variation of the surface band bending E_{sbb}) leads to an increase of the efficiency of heterojunction with intrinsic thin layer solar cells.
Zn-O-N thin films fabricated by reactive radio frequency magnetron sputtering have been investigated for their compositional, structural, transport and optical properties. In contrast to processes in which the reaction for either the oxide or the nitride is dominant, the multireaction process yields a substantially amorphous films with the Hall mobility within the range from 15 to 80 cm²/(V s). In addition, it has been observed that the Hall mobility increases for Zn-O-N. Since it has a narrower bandgap than ZnO, it is put forward that the high mobility is due to the valence band maximum in this material lying above the trap states in the gap commonly observable in ZnO. These traps originate from oxygen vacancies and are localized at the bottom of the band gap influencing the carrier mobility.
Dark-conductivity and photoconductivity properties of thermally evaporated Ga-In-Se (GIS) thin films were investigated in the temperature range of 80-430 K. All measurements were performed on as-grown and annealed GIS thin films at 300 and 400° to get information about the effect of the annealing temperature on the conductivity properties. Room temperature conductivity was obtained as 1.8 × 10^{-8} Ω^{-1} cm^{-1} for as-grown films and increased to 3.6 × 10^{-4} Ω^{-1} cm^{-1} for annealed films at 400°. Analysis of the dark-conductivity data of as-grown films revealed nearly intrinsic type of conductivity with 1.70 eV band gap energy. Temperature dependent dark conductivity curves exhibited two regions in the 260-360 and 370-430 K for both of annealed GIS films. Conductivity activation energies were found as 0.05, 0.16 and 0.05, 0.56 eV for films annealed at temperatures of 300 and 400°, respectively. The dependence of photoconductivity on illumination intensity was also studied in the range from 17 to 113 mW/cm^{2}.
Topographic and optical patterns have been fabricated in a-SiC films with a focused high-energy (1 MeV) H^{+} and He^{+} ion beam and examined with near-field techniques. The patterns have been characterized with atomic force microscopy and scanning near-field optical microscopy to reveal local topography and optical absorption changes as a result of the focused high-energy ion beam induced modification. Apart of a considerable thickness change (thinning tendency), which has been observed in the ion-irradiated areas, the near-field measurements confirm increases of optical absorption in these areas. Although the size of the fabricated optical patterns is in the micron-scale, the present development of the technique allows in principle writing optical patterns up to the nanoscale (several tens of nanometers). The observed values of the optical contrast modulation are sufficient to justify the efficiency of the method for optical data recording using high-energy focused ion beams.
Electrical properties of RF magnetron sputtered p-NiO films were characterized after fabrication and after gamma irradiations using ^{137}Cs and ^{60}Co sources. Electrical parameters are obtained from the Hall measurements, impedance spectroscopy and C-V measurement of n-Si/p-NiO junction diodes. The results show that resistivity of the NiO film is gradually increased following after sequential irradiation processes because of the decrease in holes' concentration. Hole concentration of a NiO film decreases from the original value of 4.36 × 10^{16} cm^{-3} to 2.86 × 10^{16} cm^{-3} after ^{137}Cs γ irradiation with doses of 10 Gy. In the case of γ irradiation from ^{60}Co source, hole concentration of the film decreases from 6.3 × 10^{16}/cm^3 to 4.1 × 10^{16}/cm^3 and to 2.9 × 10^{16}/cm^3 after successive expositions with a dose of 20 Gy.
We demonstrate new advantages of the space-charge-limited photocurrent technique for the investigations of charge carrier recombination. Bimolecular recombination coefficient in a-Si:H estimated according to suggested method for both electrons and holes is presented.
The increase in power density of 0.3, 0.5, 0.6, and 0.7 W cm^{-2} for hydrogenated amorphous and nanocrystalline silicon (a-Si:H and nc-Si:H) thin film samples prepared by plasma enhanced chemical vapor deposition technique causes an increase in crystalline volume fraction when the silane concentration is fixed. This increase in crystalline volume fraction is correlated to the absorption coefficient and refractive index which are determined from ellipsometric measurements. The crystallinity of samples is studied by both Raman and X-ray diffraction techniques. A mild change in the optical energy gap around an average value of 1.8 eV is noticed due to the observed change in the degree of crystallinity of the samples when power density increases. Moreover, the ambipolar diffusion length measured by the steady-state photocarrier grating technique is found to change with the increase in power density. The values of some obtained optical parameters are compared to a standard crystalline sample.
In this work, the pulse electrodeposition technique was employed for the first time to deposit AgInSe_2 films. The films were deposited at room temperature from a bath containing Analar grade 10 mM silver sulphate, 50 mM indium sulphate and 5 mM SeO_2. The deposition potential was maintained at -0.98 V (SCE). Tin oxide coated glass substrates (5.0 Ω/sq) were used for depositing the films. The duty cycle was varied in the range of 6-50%. The X-ray diffraction pattern of the thin films deposited at different duty cycles indicated the peaks corresponding to AgInSe_2. The transmission spectra exhibited interference fringes. Resistivity of the films increased from 1.5 Ω cm to 12.4 Ω cm. Mobility increased with duty cycle. Carrier density decreased with duty cycle. The photovoltaic parameters of CdS/AgInSe_2 solar cells increased with duty cycle.
Sol-gel technique was employed to prepare semiconductor tin dioxide (SnO_2) thin films. Comparatively, it gives an advantage over other techniques by its low reaction temperature, easy process and low cost. The effect of glycerin addition on the structure and preventing crack formation has been investigated. Scanning electron microscopy, atomic force microscopy, and X-ray diffraction analysis were performed to characterize nanostructured films.
In-Ga-Zn-O thin films were fabricated by means of reactive RF magnetron sputtering. Mechanism of free electrons generation via oxygen vacancies formation is proposed to determine the relationship between oxygen content in the deposition atmosphere and the transport properties of IGZO thin films. The depletion-mode a-IGZO thin film transistor with field-effect mobility of 12 cm^2/(Vs) has been demonstrated.
The possibility of using the transverse acoustoelectric phenomena in experimental investigations of near surface region in semiconductor crystals was discussed. The results of experimental investigations of GaP:Te(111) surfaces by means of the transverse acoustoelectric voltage were presented. Applying the transverse acoustoelectric voltage method, the lifetime τ of minority carrier in the near-surface region and the surface potential V_{s} in GaP:Te(111) surfaces after their different technological treatments were determined.
This paper reports the synthesis, crystal structure, surface morphology, optical and electrical properties of Mg-doped Sn₂S₃ thin films deposited by spray pyrolysis technique. All the films exhibit orthorhombic crystal structure with a (211) preferential orientation. Crystallite size calculations based on the Debye-Scherrer formula indicated that the Sn₂S₃ crystallite size increases with Mg content from 27.97 nm to 33.58 nm. Scanning electron microscopy images showed that all the films were very smooth composed of nanoneedle and nanoplate shaped grains. The band gap energy of the films exhibits a blue shift from 1.94 eV to 2.09 eV with increase in Mg concentration. Resistivity values of the undoped and Mg-doped Sn₂S₃ films were found to be in the order of 0.1 Ωcm. From the obtained results it is observed that the Sn₂S₃ film coated with 2 wt% Mg concentration exhibits better physical properties.
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