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Combining theory and computation, we explore the Goos–Hänchen (GH) effect for electrons in a single-layered semiconductor microstructure (SLSM) modulated by Dresselhaus spin–orbit coupling (SOC). GH displacement depends on electron spins thanks to Dresselhaus SOC, therefore electron spins can be separated from the space domain and spin-polarized electrons in semiconductors can be realized. Both the magnitude and sign of the spin polarization ratio change with the electron energy, in-plane wave vector, strain engineering and semiconductor layer thickness. The spin polarization ratio approaches a maximum at resonance; however, no electron-spin polarization occurs in the SLSM for a zero in-plane wave vector. More importantly, the spin polarization ratio can be manipulated by strain engineering or semiconductor layer thickness, giving rise to a controllable spatial electron-spin splitter in the field of semiconductor spintronics. [ABSTRACT FROM AUTHOR]

The primary goal of this paper is to study a few advantages of bulk nanoparticles of Cu-doped SnO2 using the solid-state reaction method. Many innovative methods were employed to evaluate the special tuning of the bandgap and other structural and morphological properties of the material. X-ray diffractometer (XRD) confirmed that tin oxide has a rutile-type tetragonal-shaped structure with space group P42 / mnm. The average crystallite size was calculated which was found to increase from 53 to 80 nm by increasing the Cu-doping from x = 0 to x = 0.30. SEM images specified that nanoparticles are inhomogeneous and densely close to each other and the average particle size was found to be in the range of ~225–430 nm. Transmission electron microscopy (TEM) images showed the grains present in a few cubic and spherical shapes and grain size was increased (~20–90 nm) with doping of copper in the SnO2 lattice. UV–Vis spectroscopy showed that the band gap increased from 3.531 to 3.701 eV for pure SnO2 and Cu-doped SnO2, respectively. XPS identified the electronic state of Sn as well as Cu atoms as 4 + and 2 + , respectively. Raman spectroscopy showed that only three vibrational modes, i.e., A1g, B2g and doubly degenerate Eg, exist in a sample. [ABSTRACT FROM AUTHOR]

The primary goal of this paper is to study a few advantages of bulk nanoparticles of Cu-doped SnO2 using the solid-state reaction method. Many innovative methods were employed to evaluate the special tuning of the bandgap and other structural and morphological properties of the material. X-ray diffractometer (XRD) confirmed that tin oxide has a rutile-type tetragonal-shaped structure with space group P42 / mnm. The average crystallite size was calculated which was found to increase from 53 to 80 nm by increasing the Cu-doping from x = 0 to x = 0.30. SEM images specified that nanoparticles are inhomogeneous and densely close to each other and the average particle size was found to be in the range of ~225–430 nm. Transmission electron microscopy (TEM) images showed the grains present in a few cubic and spherical shapes and grain size was increased (~20–90 nm) with doping of copper in the SnO2 lattice. UV–Vis spectroscopy showed that the band gap increased from 3.531 to 3.701 eV for pure SnO2 and Cu-doped SnO2, respectively. XPS identified the electronic state of Sn as well as Cu atoms as 4 + and 2 + , respectively. Raman spectroscopy showed that only three vibrational modes, i.e., A1g, B2g and doubly degenerate Eg, exist in a sample. [ABSTRACT FROM AUTHOR]

Using a quantum hydrodynamic model, quantum effects (via Bohm potential) on modulational amplification in ion-implanted semiconductor magnetoplasmas are investigated. Expressions are obtained for the threshold pump amplitude and the growth rate of modulated beam for both the electrons and implanted colloids. Numerical analysis is performed for n-InSb/CO2 laser system. The dependence of the threshold pump amplitude and the growth rate of modulated beam for electrons on wave number, applied magnetic field (via electron cyclotron frequency) and electron concentration (via electron-plasma frequency) and the dependence of the threshold pump amplitude and the growth rate of modulated beam for implanted colloids on wave number and colloid concentration (via colloid-plasma frequency) are explored. The lowering in threshold pump amplitude and enhancement of the growth rate of modulated beam for both the electrons and implanted colloids are observed by incorporating the quantum effects. The analysis provides detailed information of quantum effects on modulational amplification in ion-implanted semiconductor magnetoplasmas composed of electrons and negatively charged implanted colloids and establishes the technological potentiality of chosen samples as the hosts for the fabrication of efficient optical modulators. [ABSTRACT FROM AUTHOR]

The charge carrier concentration profile is a critical factor that determines semiconducting material properties and device performance. Dielectric force microscopy (DFM) has been previously developed to map charge carrier concentrations with nanometer-scale spatial resolution. However, it is challenging to quantitatively obtain the charge carrier concentration, since the dielectric force is also affected by the mobility. Here, we quantitative measured the charge carrier concentration at the saturation mobility regime via the rectification effect-dependent gating ratio of DFM. By measuring a series of n-type GaAs and GaN thin films with mobility in the saturation regime, we confirmed the decreased DFM-measured gating ratio with increasing electron concentration. Combined with numerical simulation to calibrate the tip–sample geometry-induced systematic error, the quantitative correlation between the DFM-measured gating ratio and the electron concentration has been established, where the extracted electron concentration presents high accuracy in the range of 4 × 1016 – 1 × 1018 cm−3. We expect the quantitative DFM to find broad applications in characterizing the charge carrier transport properties of various semiconducting materials and devices. [ABSTRACT FROM AUTHOR]

In this paper, InGaAs p-i-n photodetectors (PDs) on an InP/SiO2/Si (InPOI) substrate fabricated by ion-slicing technology are demonstrated and compared with the identical device on a commercial InP substrate. The quality of epitaxial layers on the InPOI substrate is similar to that on the InP substrate. The photo responsivities of both devices measured at 1.55 µm are comparable, which are about 0.808–0.828 A W−1. Although the dark current of PD on the InPOI substrate is twice as high as that of PD on the InP substrate at 300 K, the peak detectivities of both PDs are comparable. In general, the overall performance of the InPOI-based PD is comparable to the InP-based PD, demonstrating that the ion-slicing technology is a promising route to enable the high-quality Si-based InP platform for the full photonic integration on a Si substrate. [ABSTRACT FROM AUTHOR]

Transition metal (Mn)-doped II–VI binary (ZnS) semiconductor (Zn1−xMnxS, where, x = 0.1, 0.3, 0.5 and 0.7 M) thin films were deposited onto glass substrates using a spray pyrolysis deposition technique at 350 °C. The as-deposited film was found to be homogeneous and smooth for x = 0.3 M. Annealing temperature greatly affects the film morphology. So the effect of annealing temperature on the structural, optical and electrical properties of the Zn0.70Mn0.30S thin films was studied to explore the suitable application of these films in optoelectronics devices. The lattice defects and the internal dislocation density are found to decrease with the annealing temperature, causing improved crystallinity of the film. The decrease in dislocation density suggests an increase in the crystallinity of the film. The optical transmittance of the thin films increases with increasing annealing temperature, and the optical band gap is found to be red-shifted from 3.45 to 3.05 eV. The redshift in the band gap is due to the decrease in the amorphous phase in the thin film owning to annealing. The electrical conductivity of the films was also found to be improved by thermal treatment which may be attributed to the increased crystallinity. [ABSTRACT FROM AUTHOR]

Electron interference effects and transition from weakly localized to a strongly localized transport regime is observed in Cu doped ZnO thin films grown by pulsed laser deposition on c-sapphire substrates. The doping concentration of Cu was varied from 0% to 10%. Up to the doping concentration of ~ 0.5%, the films showed weakly localized behavior where quantum corrections to conductivity due to electron interference was active. At these doping concentrations, a transition from 3D to 2D weak localization was also observed as the measurement temperature was decreased. But at Cu concentrations of 5% and beyond, the films were found to show behavior of strong localization where the transport at low temperature was dominated by hopping mechanism. [ABSTRACT FROM AUTHOR]

Finite temperature dielectric responses of a multi-component hot carrier plasma are investigated. Spectral analyses of component-resolved electronic polarization functions and the effective dielectric function of the plasma are performed to explore their dynamic and nonlocal behaviors including the effects of finite-temperature dynamic screening of the carriers. We show that spectral behavior of dielectric response functions of a multi-component plasma are quite distinct from that of a conventional single component plasma and that, for a photo-generated hot carrier plasma of an ideal wurtzite GaN with high carrier densities, the well-defined optic plasmonic modes are clearly seen well outside the single particle excitation continuum of lighter mass electrons and that an additional low frequency acoustic plasmonic branch is located outside single particle excitation continuum of doubly degenerate heavier mass A-holes. The contribution of the heavier mass species to dressed polarization function is very similar to the case of bare polarization function. We also find that the dispersion relation of the anti-screening peaks follows that of the optical plasmon mode in a multi-component plasma. [ABSTRACT FROM AUTHOR]

Highlights: [•] Cadmium selenide (CdSe) thin films were deposited on the glass substrate by using the resistive thermal evaporation method. [•] The effect of antimony doping on physical properties of CdSe thin film has been investigated. [•] The material has been found extremely useful in the optoelectronic devices in particular with the solar cell applications. [ABSTRACT FROM AUTHOR]

Abstract: The effects of atomic oxygen exposure on electrical and field emission properties of ZnO nanowires were investigated. It was found that the turn-on field of ZnO nanowires increased after exposure to atomic oxygen. Measurement of electrical conductivity of single nanowire showed that the ozone exposure decreased the conductivity of the ZnO nanowire. Ultra-violet photoelectron spectroscopy results indicated that the ozone exposure increased the work function. Photoluminescence and X-ray photoelectron spectroscopy results suggested that ozone exposure reduced the oxygen vacancy concentration, which leads to the change in the work function and conductivity. We propose that the change of field emission properties is mainly caused by the changes in the surface work function. [Copyright &y& Elsevier]

Indium-selenium films with different thickness values, ranging from 0.13 to 1.63 μm were prepared by thermal evaporation technique. The films were deposited on heated glass substrates kept at 523 K, followed by annealing at the same temperature under high vacuum (10 Torr) for 30 min. The films remained under vacuum for 24 h after evaporation. The structural properties of the films were investigated in terms of X-ray diffraction, energy dispersive X-ray, and scanning electron microscope. The relationship between the room temperature resistivity and the film thickness was investigated. It was found that the resistivity decreased exponentially with film thickness (0.13-0.71 μm) and become constant for values of higher film thickness values. The temperature dependence of the electrical resistivity was also studied in the temperature range 300-420 K for different film thicknesses. Films with a thickness of 0.71 μm were studied for Hall-effect experiment in the temperature range 170-420 K in order to determine Hall charge carriers mobility and charge carriers concentration as well. [ABSTRACT FROM AUTHOR]

Abstract: Persistent photoconductivity is observed in ZnO single crystals and ceramics together with persistence of electron paramagnetic resonance (EPR) spectra of defects and impurity centers. It is shown that when the light is switched on and off the microwave conductivity detected from absorption of the microwave field is well correlated with the dc-conductivity measured with electrical contacts applied to the sample. The microwave photoconductivity arises together with light-induced EPR spectra and persists after switching off the light. Coexistence of the conductivity and EPR spectra shows that the photoexcited electrons cannot return back to paramagnetic centers. The persistent photoconductivity in ZnO ceramics is large in comparison with the effect observed in powders prepared from the same material and in ZnO single crystals. This suggests that surface conductivity is the dominant mechanism of persistent photoconductivity in ZnO. [Copyright &y& Elsevier]

Abstract: Heterostructures consisting of an InGaSb quantum well situated between AlGaSb barriers were grown by molecular beam epitaxy. Calculations indicate a type-I band structure with substantial valence and conduction band offsets that can allow for the confinement of either electrons or holes in the InGaSb. Quantum wells with n-type conduction were achieved using modulation doping, with Te located in the barrier above the quantum well. A set of barrier layers was found which resulted in a sample with an In0.2Ga0.8Sb quantum well that exhibited an electron mobility of 3900cm2/Vs as grown. After removal of upper barrier layers including the Te by selective etching, the conductivity switched to p-type, with hole mobilities near 800cm2/Vs. This design could allow the integration of low-power n- and p-channel field-effect transistors for complementary logic applications. [Copyright &y& Elsevier]

Abstract: Potential fluctuations due to donor–acceptor compensation have been used to observe localization–delocalization transition in semi-insulating GaAs. Photoinduced transients, resulting from relaxation of stored charges in potential valleys, have two components. The long-lived power law decay at low temperature signifies a microscopically inhomogeneous disordered phase, and single exponential decay at a higher temperature signifies a homogeneous ordered phase. Temperature dependence of steady state photocurrent and kinetics of photocurrent decay suggest percolation as a possible mechanism for photoinduced transition in semi-insulating GaAs. [Copyright &y& Elsevier]

Abstract: Undoped ZnO films of 100 nm thickness have been deposited on p-type Si (100) substrates at room temperature by radio-frequency magnetron sputtering and subsequently annealed in a rapid thermal annealing apparatus under a nitrogen ambient by varying annealing temperature (T A) from 973 to 1273 K in steps of 100 K for 3 min. Photoconductivity spectra in the UV and visible ranges are measured as a function of T A in the range of measurement temperatures (T) from 80 to 350 K under an applied bias of 1 V. For the samples annealed at T A =973 and 1073 K, negative photoconductivity is observed below T =300 K, and its absolute magnitude increases as T A increases. In contrast, the photoconductivity of the samples at T A ≥1173 K is always positive, irrespective of T, and its magnitude increases as T A increases. These PC behaviors are discussed based on the defect states at the grain boundaries of the ZnO films. [Copyright &y& Elsevier]

It is established that, in PbTe single-crystal samples annealed at 473 and 673 K, there are no acceptor levels with an activation energy of ∼0.1 eV, which are observed in unannealed samples. It is concluded that the above levels in the unannealed sample are connected with defects caused by macrostresses and a nonuniform atom distribution of extrastoichiometric tellurium along an ingot, which arise when growing PbTl crystals and are healed during annealing. [ABSTRACT FROM AUTHOR]

Abstract: SiO2 samples were implanted with 45keV Zn ions at doses ranging from 5×1015 to 1.0×1017 ions/cm2, and were then subjected to furnace annealing at different temperatures. Several techniques, such as ultra-violet–visible spectroscopy (UV–vis), grazing incidence X-ray diffraction spectroscopy (GXRD) and atomic force microscopy (AFM), have been used to investigate formation of nanoparticles and their thermal evolution. Our results clearly show that Zn nanoparticles could be effectively formed in SiO2 at doses higher than 5×1016 ions/cm2. The subsequent thermal annealing at oxygen ambient could induce the growth of Zn nanoparticles at intermediate annealing temperature range. While at temperature above 600°C, Zn nanoparticles could be transformed into ZnO, or even Zn2SiO4 nanoparticles. The results have been tentatively discussed in combination with Zn diffusion and migration obtained by Rutherford backscattering spectroscopy (RBS) measurements. [Copyright &y& Elsevier]

Abstract: First-principles calculations have been performed on the C-doped anatase TiO2. The doped TiO2 shows half-metallic properties and a 2.0 μB magnetic moment per cell. The magnetic coupling is closely related to the C–C distance. When the distance is shorter than a typical CC double bond (), the system is nonmagnetic and the dopants tend to form a cluster through a direct CC bonding interaction [Appl. Phys. Lett. 93 (2008) 132507]. When the distance is between 3.8 and , there exists strong ferromagnetic or antiferromagnetic coupling between two C atoms. The ferromagnetic coupling is induced by the bent C–Ti–C unit. When the distance is further increased, the system becomes paramagnetic. [Copyright &y& Elsevier]

Abstract: Indium antimonide crystals were synthesized from the respective component elements using the vertical Bridgman technique. The grown crystals were characterized by using X-ray analysis, EDX, electrical conductivity and thermoelectric power measurements. The calculated structural parameters for the prepared crystal have a good agreement with the standard values. Crystallite size (D) of the obtained InSb crystals was calculated to be 62.4nm. The measurements reveal higher values for Seebeck coefficient, electrical conductivity and power factor than the published results for the same compound. [Copyright &y& Elsevier]

Experimental data on the electronic properties of II–IV–V2 semiconductors irradiated with high-energy particles (electrons, protons, and neutrons) are reported. The limiting electrical characteristics of irradiated ternary compounds are evaluated and compared with the corresponding data for the binary III–V analogues of the compounds. Particular emphasis is placed on the determination of the limiting position of the Fermi level, Flim, in irradiated II–IV–V2 compounds. The results of calculations of the energy position of the intrinsic charge-neutrality level are presented. [ABSTRACT FROM AUTHOR]

Abstract: First-principle calculations based on density functional theory have been performed on the nonmagnetic 2p light element C-doped ZnO thin films. The total energies and magnetism of the system are calculated with a ten-layer slab along () direction. The results show that the C-doped ZnO thin films are ferromagnetic. A single C is preferable to occupy the subsurface site. As the concentration of C atoms increases, the ferromagnetic coupling among the dopants is more favorable, and they tend to form a cluster around the Zn atom at the film surface. The ferromagnetism is predicted to be mainly from a exchange-like coupling interaction and a exchange hybridization. The coupling interaction is the dominative mechanism. [Copyright &y& Elsevier]

Abstract: Polycrystalline CdS:In thin films were prepared by the Spray pyrolysis technique (SP) at a substrate temperature T s=490°C. The effects of annealing in nitrogen atmosphere at 400°C and HCl-etching on the electrical and structural properties of the films were investigated. The electrical properties were studied through the analysis of the I–V curves, while the structural properties were studied through the analysis of the X-ray diffraction (XRD) patterns and the scanning electron microscope (SEM) images. An increase in the films’ resistivity was occurred after annealing and/or HCl-etching, which was accompanied by changes in the XRD patterns and SEM images. These changes were related to a phase change from the mixed (cubic and hexagonal) phase to the hexagonal phase which was expected to occur during the aforementioned processes. The X-ray diffraction (XRD) patterns and the scanning electron microscope images confirm this expectation. [Copyright &y& Elsevier]

Fabrication and electrical characterisation of microscale air bridges consisting of GaN heavily doped with silicon is described. These were made from GaN–AlInN–GaN epitaxial trilayers on sapphire substrates, in which the AlInN was close to the composition lattice matched to GaN at ∼17% InN fraction. The start of the fabrication sequence used inductively coupled plasma etching with chlorine chemistry to define mesas. In situ monitoring by laser reflectometry indicated an AlInN vertical etch rate of 400 nm/minute, ∼70% of the etch rate of GaN. Processing was completed by lateral wet etching of the AlInN in hot nitric acid to leave GaN microbridges supported between anchor posts at both ends. Deposition of Ti–Au contact pads onto the anchor posts allowed study of the electrical characteristics. At low applied voltages, vertical conduction through the undoped AlInN layers was minimal in comparison with the current path through the Si:GaN bridges. Typical structures showed highly linear current-voltage characteristics at low applied voltages, and had resistances of 1050 Ω. The observed resistance values are compared with the predicted value based on materials parameters and an idealised geometry. The microbridges showed damage from Joule heating only at current densities above 2×105 A cm−2. [ABSTRACT FROM AUTHOR]

Abstract: Co0.2Al x Zn0.8−x O films prepared with different molar ratio of aluminum nitrate to zinc acetate were deposited on substrates by the sol–gel technique. X-ray diffraction, photoluminescence and ferromagnetism measurements were used to characterize the Co0.2Al x Zn0.8−x O diluted magnetic semiconductors. The authors found that the intensity of the acceptor-related photoluminescence increased with increasing aluminum concentration and an increase in the number of the acceptor-like defects (zinc vacancies especially) in the Co0.2Al x Zn0.8−x O film might lead to the enhancement of the magnetic properties. This implies that controls of the aluminum concentration and the number of the acceptor-like defects are important factors to produce strong ferromagnetism Co0.2Al x Zn0.8−x O films prepared by the sol–gel method. [Copyright &y& Elsevier]

Abstract: The electrical and microstructural properties of the PdSi based ohmic contacts on n-InP are discussed in the research. A low specific contact resistance of 2.25×10−6 Ωcm2 is obtained on Au/Si/Pd/n-InP contact after rapid thermal annealing (RTA) at 450°C for 30s. The low contact resistance can be maintained at the order of 10−6 Ωcm2 even up to 500°C annealing. From the Auger analysis, it is found that both the outdiffusion of In and the indiffusion of Si into the InP surface occurred at the ohmic contact sample. The formation of the Pd3Si compound lowered the barrier of the contact. The reactions between Pd and InP of the contact, forming In vacancies, and leading the doping of Si to the InP contact interface. [Copyright &y& Elsevier]

Ga xIn1 − xSb solid solution single crystals ( x = 0.03–0.09) have been grown. The dislocation density and electrophysical parameters are measured. A technique for the growth Ga xIn1 − xSb single crystals by the Czochralski method with GaSb polycrystal feed is developed. The conditions for the growth Ga0.08In0.92Sb single crystals with a more homogeneous distribution of Ga along the bulk are determined. [ABSTRACT FROM AUTHOR]

Abstract: Undoped zinc oxide (ZnO) films have been prepared on sapphire substrates in a molecular beam epitaxy technique, and the films were annealed in air ambient along with a GaAs wafer. Arsenic in the GaAs wafer will evaporate, and enter into the ZnO films. In this facile way, arsenic-doped p-ZnO has been obtained. Hall measurements reveal that the hole concentration and Hall mobility of the ZnO:As films obtained in this way can reach 3.7×1017 cm−3 and 2.8cm2 V−1 S−1, respectively. X-ray photoelectron spectroscopy confirms the incorporation of arsenic into the ZnO films. The activation energy of the acceptors derived from temperature-dependent Hall measurement is about 164meV. [Copyright &y& Elsevier]

Abstract: Lead iodide (PbI2) shows excellent electronic properties for detection of ionizing radiation. We report the introduction of rare-earth elements and other elements as admixtures during synthesis to study their influence on the quality of single crystals. Synthesized material as well as single crystals have been characterized by measurements of electrical resistivity and low-temperature photo luminescence and index of refraction. The structural quality with respect to polytypes was analysed by electron back scatter diffraction. Makyoh topography was applied for surface studies. [Copyright &y& Elsevier]

Abstract: We demonstrate experimentally the operation of an adaptive two-wave mixing interferometer with no field applied to a photorefractive crystal in which the quadrature condition is introduced by an external π/2 phase step. To achieve high signal to noise ratio the counter-propagating geometry for grating recording is used with a CdTe:Ge crystal, ensuring effective recording of reflection holograms. It is demonstrated that the interferometer with a photorefractive semiconductor crystal provides good sensitivity without the adverse effects that are normally associated with an applied field. [Copyright &y& Elsevier]

Abstract: Magneto-optical activity of InMnAs ferromagnetic semiconductor was measured at the fundamental gap (Γ-point) at room temperature. Reflectance magnetic circular dichroism (MCD) in the polar mode was measured in the mid-infrared from 0.12 to 0.6eV to determine s,p–d exchange interactions at the zone center (Γ-point). Well-resolved reflectance magnetic circular dichroism spectra in the mid-infrared were measured at 298K, giving direct evidence for the existence of s,p–d exchange in InMnAs at room temperature. The observed spectrum is attributed to the (Γ 8v→Γ 6c) transition at the fundamental bandgap in InMnAs. MCD was found to increase with increasing Mn concentration. The signal is strongest in the heavily Mn-doped sample, where a clear enhancement of the response is seen near the band edge (∼0.34eV). MCD increases with applied magnetic field and eventually saturates at high fields. The temperature dependence of MCD follows closely the magnetization of the films. [Copyright &y& Elsevier]

An impressive linear influence of a magnetic field on optically generated trap-recharging waves (TRW) has been observed in InP:Fe and GaAs:Cr. The phenomenon appears for the particular orientation of $\vec{B}$ parallel to the samples’ surface and orthogonal to the direction of the electric field $\vec{E}$ and wave vector of the TRW $\vec{K}$ . The results are qualitatively explained taking into account the Lorentz force and a pronounced inhomogeneity of the charge transport and of the TRW parameters. [ABSTRACT FROM AUTHOR]

The photo-electromotive force induced by a speckle pattern vibrating with large amplitude in photorefractive CdTe:V and CdTe:Ge is experimentally studied. This technique is shown to be suitable for transversal amplitude vibration measurement as well as for material response time and associated conductivity characterization. Experiments were carried out with 532 and 1064 nm wavelength illumination over a wide vibration frequency range. The results are in good agreement with a previously reported theoretical model. The studied doped crystals exhibit peculiar different features that are described and discussed. [ABSTRACT FROM AUTHOR]

Abstract: A stable low resistance aluminium (Al) contact to porous silicon (PS) could be achieved by chemically modifying PS surface with palladium chloride (PdCl2) solution. Palladium (Pd) was dispersed over the PS surface by chemical dipping method using very low concentration of PdCl2 solution (0.01M) and for a very short duration of time (5s). Field emission scanning electron microscopy (FESEM) was performed to investigate the morphology of the modified PS surface. Digital X-ray image mapping and energy dispersive X-ray (EDAX) spectras were taken to confirm the dispersion and formation of Pd clusters on the porous silicon surface. X-ray photoemission spectroscopy (XPS) confirms that the presence of oxygen is higher in Pd modified porous silicon than that of unmodified one. Aluminium (Al) was thermally evaporated on Pd modified surfaces and the study of J–V characteristics showed a linear relationship. Therefore the specific contact resistance (ρ c) could be measured by transmission line model (TLM) method. Stability of the contact was studied for a time period of around 30days and no significant ageing effect could be observed. [Copyright &y& Elsevier]

The resistivity and Hall coefficient in n-CdAs2 and p-ZnAs2 are measured at room temperature under a hydrostatic pressure as high as 9 GPa and quasi-hydrostatic pressure as high as 50 GPa. For n-CdAs2, the phase transition is found at P = 5.5 GPa, and for p-ZnAs2, two phase transitions take place; the first at P = 10–15 GPa, and the second at P = 35–40 GPa. [ABSTRACT FROM AUTHOR]

Abstract: The heterostructures of GaN/SiC/Si were prepared without using AlN or AlGaN buffer layers (AlN buffers) in the metalorganic vapor phase epitaxy of GaN on SiC. GaN (0001) with specular surface was obtained. The AlN buffers are usually used in the conventional growth of GaN on SiC due to the poor nucleation of GaN on SiC. Instead, the nucleation of GaN was controlled by varying the partial pressure of H2 in the carrier gas, the mixture of H2 and N2, during the low-temperature (600°C) growth of GaN (LT-GaN). After the LT-GaN, the high-temperature (1000°C) growth of GaN was performed using pure H2 as the carrier gas. The epitaxial film of cubic SiC (111) on a Si (111) substrate was used as the SiC template. Increasing the partial pressure of H2 in the carrier gas decreased the coverage of SiC surface by LT-GaN. It is suggested that the hydrogen atoms adsorbed on the surface of SiC is preventing the nucleation of GaN. [Copyright &y& Elsevier]

The electrical characteristics and persistent-conductivity effects in MgZnO:P alloys grown by the method of pulsed laser deposition on undoped n-ZnO substrates are systematically investigated. It is shown that the pronounced persistent conductivity and the persistent photocapacitance related to the presence of high-barrier electron traps for electron capture are observed in initial unannealed layers. These traps are located in the lower half of the band gap and have the optical ionization threshold of 2.8 eV and the electron-capture barrier height of ∼0.4 eV. Alongside such centers, the hole traps with the ionization energy of 0.14 eV are also observed. The annealing at 850°C transforms the material into that of p-type conductivity with the depth of dominant phosphorus-related acceptors close to 0.2 eV. The conductivity compensation and the formation of hole traps with the activation energy of 0.14 and 0.84 eV in the n-ZnO substrate are also observed, and these traps are associated with the acceptor-defect diffusion into the substrate at annealing. [ABSTRACT FROM AUTHOR]

Abstract: The intermediate solid solution, abbreviated as the γ-phase, exists within the CuInSe2 –2CdTe system. It has a wide homogeneity range and can be considered as a continuous solid solution between the high-temperature (HT) modification of CuInSe2 and CdTe. Single crystals of the γ-phase are grown by a modified Bridgman method. Their crystal structure and electrical properties are studied. The γ-phase crystals crystallize in the cubic structure of zinc blende (space group ) and possess intrinsic p-type conductivity with hole mobilities up to 8.29cm2/Vs. [Copyright &y& Elsevier]

Abstract: Transport properties were investigated for undoped Al0.1In0.9Sb/ InAs0.1Sb0.9 quantum wells (QWs), and two-carrier analyses were applied to the magnetic-field variations of the Hall coefficient and magnetoresistance at 77K. The Hall coefficient increases with magnetic field, which shows coexistence of electrons and holes. This behaviour is similar to AlGaAsSb/ InAs QWs, which have a type-II band structure. Additionally, the Hall coefficient turns to decrease in more than 1T, and the behaviour was not observed in the deep InAs QWs. This indicated that there are other electrons with different mobility. These are thought to be electrons extended over the QW, accumulated near the hetero-interface, and thermally excited in the barrier layer. [Copyright &y& Elsevier]

Abstract: Two-dimensional electron gas (2DEG) in AlGaAs/GaAs heterostructures, grown by molecular beam epitaxy (MBE), has been a favorite template for numerous research in a field of quantum physics during last several decades. While in the early stages the main efforts were devoted to fabricate extremely high-mobility 2DEG by concentrating on the purity of the grown material, nowadays it became clear that the further progress in the field requires new approaches of heterostructures design and the growth procedure. Here we report on the MBE growth of AlGaAs/GaAs heterostructures using a short-period superlattice (SPSL) doping instead of the more standard n-AlGaAs doping. Such doping process allows the use of a low AlAs mole fraction spacer which, in turn, leads to a lower background of impurities as well as a better interface quality. Mobility exceeding 35×106 cm2/Vs was measured in samples with doping introduced on both sides of a quantum well (QW) where the 2DEG was imbedded in. Most importantly the SPSL doping allows introducing “correlations” between ionized donors and allows controlling the potential disorder landscape that governs the appearance of various fractional quantum Hall states. [Copyright &y& Elsevier]

Abstract: In the present paper, the effects of nitridation on the quality of GaN epitaxial films grown on Si(111) substrates by metal–organic chemical vapor phase deposition (MOCVD) are discussed. A series of GaN layers were grown on Si(111) under various conditions and characterized by Nomarski microscopy (NM), atomic force microscopy (AFM), high resolution X-ray diffraction (HRXRD), and room temperature (RT) photoluminescence (PL) measurements. Firstly, we optimized LT-AlN/HT-AlN/Si(111) templates and graded AlGaN intermediate layers thicknesses. In order to prevent stress relaxation, step-graded AlGaN layers were introduced along with a crack-free GaN layer of thickness exceeding 2.2μm. Secondly, the effect of in situ substrate nitridation and the insertion of an Si x N y intermediate layer on the GaN crystalline quality was investigated. Our measurements show that the nitridation position greatly influences the surface morphology and PL and XRD spectra of GaN grown atop the Si x N y layer. The X-ray diffraction and PL measurements results confirmed that the single-crystalline wurtzite GaN was successfully grown in samples A (without Si x N y layer) and B (with Si x N y layer on Si(111)). The resulting GaN film surfaces were flat, mirror-like, and crack-free. The full-width-at-half maximum (FWHM) of the X-ray rocking curve for (0002) diffraction from the GaN epilayer of the sample B in ω-scan was 492arcsec. The PL spectrum at room temperature showed that the GaN epilayer had a light emission at a wavelength of 365nm with a FWHM of 6.6nm (33.2meV). In sample B, the insertion of a Si x N y intermediate layer significantly improved the optical and structural properties. In sample C (with Si x N y layer on Al0.11Ga0.89N interlayer). The in situ depositing of the, however, we did not obtain any improvements in the optical or structural properties. [Copyright &y& Elsevier]

Abstract: In this paper, we report the first ever experimental Compton profile study of WS2 and WSe2 employing 20 Ci 137Cs Compton spectrometer. To interpret our experimental data, the electronic properties of these compounds have been determined by linear combination of atomic orbitals, full potential linearised augmented plane-wave and spin polarised relativistic Korringa–Kohn–Rostoker (SPR-KKR) schemes. The band structure calculations show that both the WS2 and WSe2 are indirect-gap semiconductors. The SPR-KKR calculations are found to be relatively in poor agreement with the experimental electron momentum densities. The relative nature of bonding in both the dichalcogenides is explained in terms of equal-valence-electron-density profiles, Mulliken''s population and valence band charge densities. [Copyright &y& Elsevier]

The contact potential between a single ZnO nanowire and Ti/Au contacts was estimated to be ∼30 meV by considering the Arrhenious plot of the two-probe resistance, the thermionic emission conduction, and the Fowler-Nordheim tunneling model. The net voltages applied to the contacts were calculated by subtracting the four-probe voltages from the two-probe voltages at the same currents. The activation energy of the four-probe resistance was about 2.4 mV which was 1/11th of that of the two-probe resistance. The Fowler-Nordheim plot clearly showed the crossover of the conduction mechanism from thermionic emission to tunneling regime as lowering the temperatures below T<100 K. [ABSTRACT FROM AUTHOR]

Abstract: Ag-doped ZnO (ZnO:Ag) thin films were grown on glass substrates by E-beam evaporation technique. The structural, electrical and optical properties of the films were investigated as a function of annealing temperature. The films were subjected to post annealing at different temperatures in the range of 350–650°C in an air ambient. All the as grown and annealed films at temperature of 350°C showed p-type conduction. The films lost p-type conduction after post annealing treatment temperature of above 350°C, suggesting a narrow post annealing temperature window for the fabrication of p-type ZnO:Ag films. ZnO:Ag film annealed at 350°C revealed lowest resistivity of 7.25×10−2 Ωcm with hole concentration and mobility of 5.09×1019 cm−3 and 1.69cm2/Vs, respectively. Observation of a free-to-neutral-acceptor (e,Ao) and donor–acceptor-pair (DAP) emissions in the low temperature photoluminescence measurement confirms p-type conduction in the ZnO:Ag films. [Copyright &y& Elsevier]

Abstract: The effect of the dual acceptors (Mn and Be) on ferromagnetism in -doped GaAs/AlAs digital ferromagnetic heterostructures (DFH) has been studied by ab initio calculations. The dependence of the electronic and magnetic properties on both doping acceptor positions in the well and in the barrier are reported in the two-dimensional hole gas system, respectively. Our results also show that the -doping Mn layer in the well edge of the DFH is potential for high Curie temperature of a diluted magnetic semiconductor (DMS). The hole distributions and the magnetic moments are analyzed in terms of their orbital projected density of states. The ferromagnetic coupling is attributed to the overlap of the hole gases and the magnetic layer. However, the Be -doping layer in AlAs barrier strongly suppresses the ferromagnetic coupling in the DFH, the origin is not from the electrical doping impurities, but rather be the result of some structural modifications due to the presence of the Be. [Copyright &y& Elsevier]

Abstract: Unintentionally doped GaN with conventional single low-temperature (LT) AlN buffer layer and with double Mg x N y /AlN buffer layers both were prepared. It was found that we could reduce defect density and thus improve crystal quality of the GaN by using double Mg x N y /AlN buffer layers. GaN with double Mg x N y /AlN buffer layers reveals an asymmetrical reflection (102) and (002) with a smaller full-width at half-maximum (FWHM), and a higher mobility, lower background concentration and lower etching pit density (EPD) than the GaN with the LT-AlN buffer layer. [Copyright &y& Elsevier]

In the present paper, the effect of in-situ substrate nitridation time on crystalline quality of GaN films grown on Si (111) substrates by metal organic chemical vapor deposition (MOCVD) were investigated. A thin buffer layer of silicon nitride (SiN x ) with various thicknesses was achieved through the nitridation of substrate at different nitiridation times ranging from 0 to 660 s. The structural characteristics, such as dislocation densities, correlation lengths of columnar crystallites, the tilt and twist of the mosaic structure, and the angles of rotational disorder, were all studied in detail by using a planar and cross-sectional view of high resolution transmission electron microscopy (HRTEM) and X-ray diffraction (HRXRD) performed at different scattering geometries. It was found that the dislocation densities, lateral coherence lengths, vertical coherence lengths, and the tilt and twist of mosaic blocks in GaN films monotonically varies with the nitridation time. The experimental findings showed that the nitridation times had more influence on edge dislocation densities than the screw type. [ABSTRACT FROM AUTHOR]