Electron scattering with spin flip in indium antimonide and indium arsenide

The longitudinal magnetoresistance has been investigated at temperatures in the range from 2.8 to 200 K in a magnetic field of up to 200 kOe with the aim of determining the temperature range and the magnetic field strength at which charge carrier scattering with spin flip occurs in n-type indium arsenide and n-type indium antimonide. It is established that quantum oscillations of the longitudinal magnetoresistance of indium arsenide exhibit weak zero maxima due to electron scattering with spin flip at temperatures in the range from 4 to 35 K in a magnetic field of 146 kOe. For the longitudinal magnetoresistance of indium antimonide, zero maxima caused by electron scattering with spin flip are revealed in the temperature range from 60 to 80 K in a magnetic field of 132 kOe.     

Mechanism of current flow in alloyed ohmic In/GaAs contacts

A mechanism of current flow in an alloyed ohmic In contact to low-doped gallium arsenide (n = 4 × 10¹⁵ cm^?3) is studied. From the temperature dependence of the contact resistance per unit surface area, it is found that the basic mechanism of current flow is thermionic emission through a potential barrier 0.03 eV in height.     

Mechanical stresses during the formation of MDS structures on indium arsenide

A study is made of the mechanical stresses arising during all the stages of fabrication of dielectric—semiconductor structures on indium arsenide with an anodic oxide. It is shown that grinding, electrodynamic polishing, and oxidation lead to the appearance in the semiconductor of tensile stresses and in the anodic oxide of compressive stresses, which may be one possible cause of the high density of surface states in MDS structure on indium arsenide with an anodic oxide.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 12, pp. 87–89, December, 1994.     

Atomistic simulation of temperature dependent thermal transport across nanoconfined liquid

Non-equilibrium classical molecular dynamics simulation was carried out to study the temperature dependence of thermal transport across nanogap confined liquid. The research was focused on the temperature response behavior of nanoconfined liquid subjected to different temperature environment. The simulation was carried out with simplified molecular model. It was found that the molecular mobility and thermal conductance of liquid reduces significantly due to the confinement in a nanometer scale cavity. The simulation also reveals that thermal resistance responses oppositely to the change in temperature for the nanoconfined liquid compared to the bulk liquid; thermal resistance of the nanoconfined liquid was observed to decrease with the increase of temperature following a power law relation (R_t/R_{t_inital}∼0.9837(T/T_initial)^−0.617) whereas it increases for the bulk liquid. Thermal resistance of the confined liquid and its dependence on temperature was also observed to strongly depend on the gap thickness.     

Effect of C60 fullerene, fullerene-containing soot, and other carbon materials on the sliding edge friction of metals

A comparative study of different carbon materials (C₆₀ fullerene; soot, both with and without fullerenes; graphite; and industrial carbon black) as additives to industrial lubricating oils has been carried out for copper-steel and steel-steel sliding couples. The soot containing fullerene and the powder of pure fullerene produce a noticeable improvement in the antifriction and antiwear properties of steel-steel and steel-copper couples, especially under heavy loads and pressures at the contact. The greatest improvement was observed for the steel-steel couple. Structural-mechanical studies were carried out for copper riders and it has been demonstrated by several methods that the addition of the C₆₀ fullerene (pure fullerene or as a fullerene-containingsoot) creates a fullerene-polymer film on the frictional surface about 1000 Å thick, which has a protective effect.     

Numerical study of the thermal processes occurring in materials under irradiation with high-energy heavy ions

Numerical simulation of the thermal processes occurring in indium phosphide under the action of a heavy gold ion with the energy E ₀ = 200 MeV is carried out. The problem is solved taking into account phase transitions of the melting and evaporation types. Numerical studies are carried out on the basis of a modified thermal-peak model and the obtained results are analyzed.     

Reduction of n‐type diamond contact resistance by graphite electrode

The contact resistance between heavily phosphorus doped n‐type (n⁺‐type) diamond (111) layers and graphite electrodes was investigated. To analyze the contact resistance properties in detail in the low‐voltage region, the transfer length method including nonlinear terms with a constant current was analyzed based on the double Schottky contact configuration. Using this method, we have revaluated the metal contact resistance reported previously. Using the graphite electrodes, the linearity of current‐voltage characteristics was improved. The contact resistance was reduced by a factor of ten compared to that of conventional Ti/Pt/Au electrodes. The graphite electrodes were formed directly by thermal annealing at 1300 °C for 10 min from an n⁺‐type diamond surface. (© 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Operation performance characteristics of vertical-cavity surface-emitting lasers (VCSELs) under high thermal neutron irradiated fields

To operate and read out even the innermost detectors under any particular conditions, electronics and optical components must be developed accordingly. For semiconductor lasers, on which we will concentrate here, it has been found that an inner temperature increase has a direct impact on the light power emitted by the device. It was found that the effects of radiation on the behavior of semiconductor lasers are convolved with those of temperature. An optimized coupling to the cooling of the laser device reduces the thermal effects in the material. Therefore, a test stand to qualify the effect of heat in the device and the adoption of the heat sink is realized. In this paper, we create a model describing the degradation of the light power and voltage characteristic of a semiconductor-laser undergoing irradiation where the high temperature effects are taken into account. This VCSEL-device model can be used to predict the behavior and operation-performance characteristics (rise time, 3 dB bandwidth, light power, resonance frequency, and transmission bit rate) of a laser being irradiated with different neutron doses. We check the robustness of the model against the high fluence (in excess of 10¹⁵ neutrons/cm²). We take into account the study of different semiconductor- and polymeric material-based VCSEL devices such as aluminum gallium arsenide (AlGaAs), indium gallium arsenide phosphors (InGaAsP), and polymeric polymethylmethacrylate (PMMA) under the same operating conditions.     

InSe electrical characterization by means of transport parameters

SCLC measurements in single crystals of the layered semiconductor n-type InSe are reported. The measurements were carried out at various temperatures and on samples grown with indium added in excess (from 5 to 10%). The experimental results suggest that the trapping levels location and the charge transport are dependent on the indium excess. Only the samples grown with an indium excess of about 5% show the features typical of intrinsic semiconductors. The anomalous behaviour of samples grown with indium excess between 6 and 10 is explained by means of scattering mechanisms between charge carriers and ionized impurity centers.     

Range of recoil atoms in isotropic stopping materials

A calculation of the stopping power, range, and range straggling of low energetic atoms (E?1 MeV) is reported. The computation applied the biatomic repulsive potential of Firsov and thus had to be carried out numerically. The results, however, are presented in an analytical form. — Experimental checks were performed with recoil atoms. 96 keV Ra-224 atoms from the α-decay of Th-228 were used to measure the range distributions in several light gases. — The fast neutron induced reactions, such as (n, p)-or (n, α)-reactions, led to recoils of higher energies (up to more than 1 MeV). Their mean ranges in polycrystalline metals or amorphous oxide layers could be obtained by measuring the fraction of radioactive recoils which had left the target surface. — The experimental data are in good agreement with the theory, except at the highest energies where the observed ranges are slightly larger than predicted.     

Microscopic structure of semiconductor surfaces

To study the initial reaction steps of hydrogen, oxygen, and water, on differently prepared single crystal surfaces of silicon, germanium/silicon alloys, indium phosphide and gallium arsenide, we used high-resolution electron energy-loss spectroscopy (HREELS) in combination with low-energy electron diffraction (LEED), X-ray photoelectron spectroscopy (XPS) and Auger electron spectroscopy (AES). Very recently, we started a program on the hydrogenation of III–V compound semiconductors, and on the oxidation of Si and III–V compound semiconductors, using alkali metals as a catalyst. This paper summarizes the present stage of our investigations, describing in particular aspects of the microscopic structure of differently prepared semiconductor surfaces.     

Determination of ionicity in zinc phosphide and zinc arsenide by X-ray absorption method

K-absorption edges and associated extended fine structure is recorded using a 40 cm, automatic scanning X-ray spectrometer for zinc in zinc phosphide and zinc arsenide. The bond lengths for these compounds are determined using Lytle and Chivate et al.'s method. The convalent energy gaps in Phillips' theory are evaluated on the basis of Levine's extension to Phillips theory for these complex compounds. The X-ray absorption edge shifts for zinc in both of these compounds and the ionic energy gap determined using Levine's method are in good agreement. Hence, ionicities for these compounds were determined. The ionicity value for zinc phosphide comes out to be 0.17 and for zinc arsenide 0.16.     

Specific contact resistance of IGZO thin film transistors with metallic and transparent conductive oxides electrodes and XPS study of the contact/semiconductor interfaces

In this work, the specific contact resistance (ρ_c) between amorphous indium-gallium-zinc-oxide (IGZO) semiconductor and different contact electrodes was obtained from thin film transistors (TFTs). Ti/Au (10/100 nm), aluminum doped zinc oxide (AZO, 100 nm) and indium tin oxide (ITO, 100 nm) were used as source/drain electrodes to fabricate IGZO TFTs. Chemical states of the contacts/semiconductor interfaces were examined by depth profile X-ray photoelectron spectroscopy (XPS) analysis to explain the origin of the differences on specific contact resistance. The lowest ρ_c achieved using Ti/Au was related to the formation of a TiO_x interlayer due to oxygen atoms diffusing out from the semiconductor under layer, increasing the carrier concentration of IGZO at the interface and lowering the ρ_c. On the contrary, no interfacial reactions were observed between IGZO and AZO or ITO source/drain. However, IGZO resistivity increased with ITO contacts likely due to oxygen vacancies filling during ITO deposition. This fact seems to be the origin of the high contact resistance between IGZO and ITO, compared to IGZO-AZO and IGZO-Ti/Au interfaces.     

Superconducting Properties of Indium Nanostructured in Pores of Thin Films of SiO<Subscript>2</Subscript> Microspheres

Samples of a superconducting indium nanocomposite based on a thin-film porous dielectric matrix prepared by the Langmuir–Blodgett method are obtained for the first time, and their low-temperature electrophysical and magnetic properties are studied. Films with thickness b ≤ 5 μm were made from silicon dioxide spheres with diameter D = 200 and 250 nm; indium was introduced into the pores of the films from the melt at a pressure of P ≤ 5 kbar. Thus, a three-dimensional weakly ordered structure of indium nanogranules was created in the pores, forming a continuous current-conducting grid. Measurements of the temperature and magnetic field dependences of the resistance and magnetic moment of the samples showed an increase in the critical parameters of the superconductivity state of nanostructured indium (critical temperature T_c ≤ 3.62 K and critical magnetic field H_c at T = 0 K H_c(0) ≤ 1700 Oe) with respect to the massive material (T_c = 3.41 K, H_c(0) = 280 Oe). In the dependence of the resistance on temperature and the magnetic field, a step transition to the superconductivity state associated with the nanocomposite structure was observed. A pronounced hysteresis M(H) is observed in the dependence of the magnetic moment M of the nanocomposite on the magnetic field at T < T_c, caused by the multiply connected structure of the current-conducting indium grid. The results obtained are interpreted taking into account the dimensional dependence of the superconducting characteristics of the nanocomposite.     

Metal-ceramic contact angles determined by thin film techniques

A method of estimating contact angles is described in which 1000 A thick layers of metals are condensed from the vapour. If condensation takes place at temperatures greater than about 0.8 T_m the film is observed to break up into drops which are approximately segments of spheres, and the contact angle may be calculated from measurements on the drop size when the average film thickness is known. The experimental method is straightforward and relatively very fast, yet gives results in good agreement with earlier measurements. Results for the following metals on sapphire are presented: Al, Ag, Au, Cu, In, Sn. In addition results for Al on quartz are discussed, and it is suggested that the method may give meaningful results even when, as in this case, chemical reaction takes place.     

Performance improvement in pentacene organic thin film transistors by inserting a C60 ultrathin layer

The contact effect on the performances of organic thin film transistors is studied here. A C₆₀ ultrathin layer is inserted between Al source--drain electrode and pentacene to reduce the contact resistance. By a 3 nm C₆₀ modification, the injection barrier is lowered and the contact resistance is reduced. Thus, the field-effect mobility increases from 0.12 to 0.52 cm²/(V·s). It means that inserting a C₆₀ ultra thin layer is a good method to improve the organic thin film transistor (OTFT) performance. The output curve is simulated by using a charge drift model. Considering the contact effect, the field effect mobility is improved to 1.15 cm²/(V·s). It indicates that further reducing the contact resistance of OTFTs should be carried out.     

In situ Mössbauer spectroscopic study of iron III chloride intercalated in graphite under reaction conditions

In situ⁵⁷Mössbauer spectroscopy has been used to study the process of reduction and Fischer-Tropsch reactions on FeCl₃ intercalated in graphite layers. It is found that on flowing H₂ on graphite intercalated by FeCl₃ at 400° C, FeCl₃ converts to FeCl₂ and partly to small particles of α-Fe. The Mössbauer spectra of the reduced sample are superposition of a sextuplet and two quadrupole doublets indicative of metallic iron and two species of FeCl₂. However, at room temperature and at 400° C for a short period of reduction the magnetic hyperfine splittings (ca. 295 kOe and 262 kOe respectively) are smaller than the corresponding parameters for bulk metallic iron. The differences have been attributed to the interaction between the monolayers of iron atoms and the carbon nets of the graphite support. When the reduction was carried out for a longer period, α-Fe was formed. When a sample reduced for a short period of time is heated at 400°C in the presence of the synthesis gas, part of the iron particles sinter, and α-iron is observed. On heating the above sample once again at 400°C in the presence of the synthesis gas, the remaining small particles of iron are totally converted to the bulk phase (α-Fe). Experimental observations indicate that α-Fe and FeCl₂ are present on the surface as well as inbetween the intercalated graphite layers.     

Growth and properties of GaInPSbAs isoperiodic solid solutions on indium arsenide substrates

The results on the growth of GaInPSbAs isoperiodic solid solutions on indium arsenide substrates from the liquid phase in a field of temperature gradient have been discussed. The heterophase equilibria in the Ga–In–P–Sb–As system have been analyzed in the framework of the regular solution model. The kinetics of the growth, the composition, the structural perfection, and the luminescence properties of Ga_zIn_1–zP_xSbyAs_1–x–y/InAs isoperiodic heterostructures have been investigated.     

Reflectance anisotropy spectroscopy of metal nanoclusters formed on semiconductor surface

Optical anisotropy of indium nanoclusters formed on the (001) surface of indium arsenide was found by differential reflectance anisotropy spectroscopy. The fact of such an observation for nanocluster arrays unambiguously evidences the presence of their macroscopic anisotropy which could not be disclosed by conventional diagnostics techniques. The scale of the observed plasmonic anisotropy signal exceeds by two orders of magnitude the scale of anisotropy signals from valence-bond structures formed on a semiconductor surface. A resonant feature observed in reflectance anisotropy spectra is interpreted in the model of coupled dipole plasmons belonging to ellipsoidal nanoparticles. Estimation based on the experimental spectra shows that within the sample surface the lengths of ellipsoid semiaxes differ from each other by a few percent.     

金属-块状半导体的接触电阻率——四点结构模型

本文提出一种测量金属-半导体体样品的接触电阻率ρ_c的方法——四点结构模型。四个金属电极的排列不受任何限制,导出了ρ_c的表达式。如果样品不是半无限大,而是有一定厚度的薄片,则必须进行修正,给出了修正因子。根据这个模型,进行实验测量和计算,所得结果与文献报道的一致。 关键词：