The annealing of heavily doped GaAs:Te can significantly change the free electron concentration in a reversible manner. These changes of electrical properties are accompanied by the structural changes of GaAs:Te solid solution. We used X-ray Absorption Fine Structure at K-edge of tellurium to determine local changes around Te atoms for different states of the GaAs:Te crystals caused by the annealing corresponding to different electron concentrations. The best EXAFS fit for the samples with high electron concentration was obtained for the substitutional Te_{As} model with elongated Te-Ga bonds (as compared to the As-Ga distance). For the samples in the low concentration state the best fit was for the pairs of Te atoms forming a rhombohedral symmetry double-DX centre, with the proportional admixture of the substitutional tellurium
The paper deals with the investigations of structural properties of Zn_{1-x}Mn_xTe films, which were fabricated under various deposition conditions using the thermal evaporation method in a closed volume. The surface morphology of the samples was studied, the phase analysis of their structures was performed, the elemental analysis of the films and the crystal lattice constant were investigated. The texture perfection of the films before and after copper ion implantation was evaluated.
The results of X-ray, scanning electron microscopy and atomic force microscopy studies of near-surface regions of (111) Hg_{1-x}Cd_{x}Te (x = 0.223) structures are presented. These structures were obtained by low-energy implantation with boron and silver ions. TRIM calculation of the depth dependences of impurity concentration and implantation-induced mechanical stresses in the layer near-surface regions has revealed that the low-energy implantation of HgCdTe solid solution with elements of different ionic radiuses (B^{+} and Ag^{+}) leads to the formation of layers with significant difference in thickness (400 nm and 100 nm, respectively), as well as with maximum mechanical stresses differing by two orders of magnitude (1.4 × 10^3 Pa and 2.2 × 10^5 Pa, respectively). The structural properties of the Hg_{1-x}Cd_{x}Te epilayers were investigated using X-ray high-resolution reciprocal space mapping.
In this study, tin oxide (SnO₂) coatings on Cr coated stainless steel and multi-walled carbon nanotube (MWCNT)/graphene substrates were prepared using a radio frequency magnetron sputtering process as anode materials in lithium-ion batteries. SnO₂ thin film and SnO₂/MWCNT/graphene composite were characterized with field-emission scanning electron microscopy, X-ray diffraction, and electrochemical tests (cyclic voltammetry and galvanostatic cycling). The electrochemical properties of SnO₂ and SnO₂/MWCNT/graphene composite anodes were studied using 2016-type coin cells assembled in an argon-filled glove box. The cells were cyclically tested on a MTI BST8-MA battery analyzer. The cyclic voltammograms of SnO₂ anode and SnO₂/MWCNT/graphene composite anode were obtained over the potential range of 0.05-3.0 V and 0.05-2.5 V at a scan rate of 0.05 mV s¯¹, respectively.
ZnO nanowires doped with Mg have been successfully prepared on Au-coated Si (111) substrates using chemical vapor deposition method with a mixture of ZnO, Mg, and activated carbon powders as reactants at 850°C. The structural, compositional, morphological and optical properties of the samples were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, high-resolution transmission electron microscopy, and photoluminescence spectroscopy. The nanowires are single crystalline in nature and preferentially grow up along [0001] direction with the average diameter and length of about 60 nm and several hundred micrometers, respectively, thinner and longer than the results of literature using the similar method. Room temperature photoluminescence spectroscopy shows a blueshift from the bulk band gap emission, which can be attributed to Mg doping that were detected by energy dispersive X-ray analysis EDX in the nanowires. Finally, the possible growth mechanism of crystalline ZnO nanowires is discussed briefly.
The paper describes the production of doubly charged ions from solids and gases using a hollow cathode ion source with an internal evaporator heated by a spiral cathode filament and arc discharge. The obtained currents were 15 μA for Bi^{2+}, 10 μA for As^{2+} and Al^{2+}, 8 μA for Kr^{2+} and Xe^{2+}, 5 μA for In^{2+} and Ge^{2+}, enabling moderate dose implantations ( ≈ 10^{15} cm^{-3}) with doubly charged ions. Characteristics of the ion source are presented and discussed in order to choose the optimal working parameters. A brief presentation of numerical model of doubly and singly charged ions in the ion source is given. The calculated results (dependences of ion current on the anode voltage) are in good agreement with the experimental data.
The semi-isolating GaAs (100) samples irradiated with fluence 3 × 10^{15} ions/cm^{2} of In^{+} ions were characterized by using the methods: Rutherford backscattering spectroscopy, nuclear reaction analysis and ellipsometric spectroscopy. The values of the thicknesses layers enriched with oxygen and the implanted were determined by the methods of nuclear reaction analysis and Rutherford backscattering spectroscopy. Multilayer models were applied for determination of the optical constants (refraction and extinctions coefficients) of investigated samples. The thickness of native oxide covering the surface of implanted GaAs and refraction coefficients were increased after implantation with indium. The spectrum of extinction indexes as a function of light wavelength has two bands near the light wavelengths 400 nm and 480 nm. The observed effects can be interpreted as formation of local oxides of In and InAs precipitates or ternary alloys in enriched with oxygen layers at the surfaces of implanted GaAs.
The article presents the results of research on alternating-current electrical conduction in phosphorus-doped silicon, strongly defected by the implantation of Ne^{++} neon ions. An analysis of electrical properties recorded at the annealing temperature of T_{a} = 373 K and affected by the changes of testing temperature ranging from 253 K to 368 K as well as frequency from 50 Hz to 5 MHz has been discussed. The obtained results have confirmed the occurrence of two conduction mechanisms in strongly defected semiconductors: the band conduction mechanism that is characteristic of low frequency values and the jump conduction one that corresponds to higher frequencies.
The article presents the experimental results on electric conductivity investigations of gallium arsenide, exposed to polyenergy implantations with H^{+} ions, depending on alternating current frequency (50 Hz ÷ 5 MHz), testing temperature (liquid nitrogen temperature ÷ 373 K) and the temperature of 15 min isochronous annealing (293 ÷ 663 K). It has been found that the obtained dependences σ (T_{p}, f) result from a jump mechanism of electric charge transfer between the radiation defects that form in the process of ion implantation. Correlations between annealing of various types of radiation defects and conductivity characteristics σ (T_{p}, f) have also been discussed.
In this study, the reversible capacities, as well as the cycling behavior, of crystalline antimony-doped tin oxide (ATO) films have been investigated. ATO films were deposited on Cr-coated stainless steel substrates by the RF magnetron sputtering technique, with antimony-doped tin oxide (SnO₂:Sb) target in a mixed oxygen/argon gas environment. The ATO films were deposited for 1.0 h in a mixture of Ar and O₂ environment with O₂/Ar ratio of 10/90, at sputtering power of 75 W, 100 W and 125 W RF. ATO films were examined by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM). The electrochemical properties of ATO anodes were studied using 2016-type coin cells assembled in an argon-filled glove box.
Cadmium sulfide, copper sulfide and zinc sulfide films were grown on Si(111) substrate by successive ionic layer adsorption and reaction method at room temperature. The crystalline structure and morphology of obtained films were characterized by X-ray diffraction, scanning electronic microscope and energy dispersive X-ray analysis methods. The films were polycrystalline and showed preferred orientation. The surface morphology of these films looked relatively smooth and homogeneous in the scanning electron microscope image. The energy dispersive X-ray analysis spectra showed that the expected elements exist in the thin films.
The article describes the results of the research on thermal stability of electrical parameters of n-type gallium arsenide doped with tellurium, defected by ion implantation, measured at the operating temperature ranging from 77 K to 373 K. The aim of the work is to investigate the character of changes in the values of such electrical parameters as resistivity, capacity and loss tangent of the tested GaAs samples, exposed to different thermal conditions. Temperature dependences analyzed in the paper could be taken as a basis to formulate general speculations concerning potential applications of the tested material as a substrate in the process of photovoltaic cells production. The phenomenon of conversion of solar energy into electricity is strongly connected with electrical properties of photovoltaic cell substrate material and its internal structure. Moreover, the efficiency of photoconversion is affected by such factors as charge carrier lifetime distribution and diffusion length in the base material. Therefore, it is necessary to confirm what is the character of the influence of operating temperature on the electrical parameters of GaAs and what modification could be introduced in the material in order to increase the efficiency of photoconversion.
A new construction of a hollow cathode ion source equipped with an internal evaporator heated by a spiral cathode filament and arc discharge is presented. The source is especially suitable for production of ions from solids. The proximity of arc discharge region and extraction opening enables production of intense ion beams even for very low discharge current (I_{a} = 1.2 A). The currents of 50 μA (Al^{+}) and 70 μA (Bi^{+}) were obtained using the extraction voltage of 25 kV. The source is able to work for several tens of hours without maintenance breaks, giving possibility of high dose implantations. The paper presents the detailed description of the ion source as well as its experimental characteristics like dependences of extracted currents and anode voltage on anode and cathode currents.
Simple electric transport versus T = 20-400 K in metallic n-GaAs annealed single crystals with Te impurity concentration ∿(0.4-1.7) × 10^{19} cm^{-3}, which is above the equilibrium doping limit, is reported and compared with modern theory of electron mobility in degenerated n-GaAs by Szmyd, Hanna, Majerfeld. An overcome of the equilibrium doping limit in annealed n-GaAs is manifested by a lowered electrical activation of Te donors and by an onset of ≈ 0.1-1 μm regions of local strain in the crystal lattice known from high resolution X-ray studies. These preliminary results of transport show that the electron mobility μ(T) measured for n-GaAs with local strains is not consistent with predictions of Szmyd et al. model for any degree of compensation assumed. This surprising result indicates that electric transport in materials above the equilibrium doping limit is not well understood assuming the scattering by ionized impurities. The nature of defects responsible for an observed strong reduction of free carrier concentration (here ≈ 80%) in annealed heavily doped n-GaAs seems not to be related with electrical compensation. We point here at the possible role of effects of free carrier scattering due to static lattice distortions (local strains) related to a chemical aggregation of impurity atoms. We also notice that transport in metallic n-GaAs with local strains shows features similar to a weak localization σ_{xx} ∝ log T.
Semi-insulating GaAs wafers have been implanted with 250 keV In^{+} ions at a fluence of 3 × 10^{16} cm^{-2}. The samples prepared in this way were subsequently annealed at a temperature of 600°C or 800°C for 2 h. Thicknesses of the native oxide layers on implanted GaAs after samples storage in air were evaluated using the Rutherford backscattering spectrometry with the nuclear reaction O^{16}(α,α)O^{16} method. The chemical composition of native oxide layers on In^{+} implanted and annealed GaAs has been studied using X-ray photoelectron spectroscopy. As_{2}O_{3}, As_{2}O_{5}, Ga_{2}O_{3}, GaAs, InAs and InAsO_4 compounds were detected in these layers.
A new method of refractory metal (like Mo and Ta) ion beam production using the arc discharge ion source and CCl₂F₂ (dichlorodifluoromethane) used as a feeding gas supported into the discharge chamber is presented. It is based on etching of the refractory metal parts (e.g. anode or a dedicated tube) Cl and F containing plasma. The results of measurements of the dependences of ion currents on the working parameters like discharge and filament currents as well as on the magnetic field flux density of an external electromagnet coil are shown and discussed. The separated Mo⁺ and Ta⁺ beam currents of approximately 22 μA and 2 μA, respectively, were obtained.
The article presents the outcome of the research on alternating-current electric conduction in silicon doped with boron, phosphorus, and antimony of resistivities ρ=0.01 Ω cm and ρ=10 Ω cm, strongly defected by the implantation of Ne^{+} ions (D=1.5 × 10^{14} cm^{-2}, E=100 keV). On the basis of results obtained for samples annealed at the temperature T_{a}=598 K and measured at the testing temperature T_{p}=298 K and frequency f=1 MHz it was possible to carry out an analysis of mechanisms of electric conduction depending on the type and concentration of dopant. Obtained results confirmed the occurrence of hopping conductivity mechanism in strongly defected semiconductors, which is typical for high frequency values.
A new method of Mo^{+} ion beam production is presented in the paper. The method bases on the chemical sputtering/etching of the molybdenum parts (e.g. anode) of the arc discharge ion source by the chloride containing plasma. A mixture of CCl_4 (or CHCl_3) vapor and air was used as the feeding substance. The separated Mo^{+} beam current of approximately 18 μA was achieved. The measurements of the ion current dependences on the discharge and filament currents as well as on the magnetic field flux density from the electromagnet surrounding the discharge chamber were performed in order to find the optimal working parameters of the ion source.
Amplification of an acoustic wave is considered in magnetised piezoelectric n-type semiconductor plasma under quantum hydrodynamic regime. The important ingredients of this study are the inclusion of quantum diffraction effect via the Bohm potential, statistical degeneracy pressure, and externally applied magnetostatic field in the momentum balance equation of the charged carriers. A modified dispersion relation is derived for evolution of acoustic wave by employing the linearization technique. Detailed analysis of quantum modified dispersion relation of acoustic wave is presented. For a typical parameter range, relevant to n-InSb at 77 K, it is found that the non-dimensional quantum parameter H reduces the gain while magnetic field enhances the gain of acoustic wave. The crossover from attenuation to amplification occurs at (ϑ₀/ϑₛ)=1 and this crossover point is found to be unaffected by quantum correction and magnetic field. It is also found that the maximum gain point shifts towards lower drift velocity regime due to the presence of magnetic field while quantum parameter H shifts this point towards higher drift velocity. Numerical results on the acoustic gain per radian and acoustic gain per unit length are also illustrated. Our results could be useful in understanding acoustic wave propagation in magnetised piezoelectric semiconductor in quantum regime.
In the paper, measurements of surface tension of solutions used for silicon etching and results of etching in the solutions are presented. Based on the obtained results, the analysis of interactions of surfactants with differently oriented silicon planes has been carried out.
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