Measurement of Electron Spin Lifetime and Optical Orientation Efficiency in Germanium Using Electrical Detection of Radio Frequency Modulated Spin Polarization

We propose and demonstrate a technique for electrical detection of polarized spins in semiconductors in zero applied magnetic fields. Spin polarization is generated by optical injection using circularly polarized light which is modulated rapidly using an electro-optic cell. The modulated spin polarization generates a weak time-varying magnetic field which is detected by a sensitive radio-frequency coil. Using a calibrated pickup coil and amplification electronics, clear signals were obtained for bulk GaAs and Ge samples from which an optical spin orientation efficiency of 4.8% could be determined for Ge at 1342 nm excitation wavelength. In the presence of a small external magnetic field, the signal decayed according to the Hanle effect, from which a spin lifetime of 4.6 +/- 1.0 ns for electrons in bulk Ge at 127 K was extracted.

Optical, electrical and dielectric properties of TiO(2)-SiO(2) films prepared by a cost effective sol-gel process

Titanium dioxide (TiO(2)) and silicon dioxide (SiO(2)) thin films and their mixed films were synthesized by the sol-gel spin coating method using titanium tetra isopropoxide (TTIP) and tetra ethyl ortho silicate (TEOS) as the precursor materials for TiO(2) and SiO(2) respectively. The pure and composite films of TiO(2) and SiO(2) were deposited on glass and silicon substrates. The optical properties were studied for different compositions of TiO(2) and SiO(2) sols and the refractive index and optical band gap energies were estimated. MOS capacitors were fabricated using TiO(2) films on p-silicon (1 0 0) substrates. The current-voltage (I-V) and capacitance-voltage (C-V) characteristics were studied and the electrical resistivity and dielectric constant were estimated for the films annealed at 200 degrees C for their possible use in optoelectronic applications. (C) 2011 Elsevier B.V. All rights reserved.

La-Doped Ba2In2O5 Electrolyte: Pechini Synthesis, Microstructure, Electrical Conductivity, and Application for CO Gas Sensing

Dense (Ba1―xLax)2In2O5+x (BLIO) electrolytes with different compositions (x = 0.4, 0.5, 0.6) were fabricated using powders obtained by the Pechini method. The formation of BLIO powders was investigated by using X-ray diffraction and scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy. The calcination temperature and time were optimized. The sintered (Ba1―xLax)2In2O5+x electrolytes showed a relative density greater than ∼97%, and the major phase of three electrolyte compositions was indexed as a cubic perovskite. The electrical conductivity of BLIO ceramics at elevated temperatures in air was measured by ac-impedance spectroscopy. The activation energies for conduction in BLIO were 102 kJ mol―1 between 473 and 666 K and 118 kJ mol―1 between 769 and 873 K, which are comparable to that for 8 mol % yttria-stabilized cubic zirconia. Mixed-potential gas sensors utilizing BLIO-based electrolytes exhibited good sensitivity to different CO concentrations from ∼100 to ∼500 ppm and excellent selectivity to methane at around 873 K.

Anisotropic electrical transport property in La4BaCu5O13+δ and La4BaCu4NiO13+δ epitaxial thin films

Epitaxial films of La4BaCu5O13+δ and La4BaCu4NiO13+δ oxides are grown with a-b plane parallel to (100) of LaAlO3 and SrTiO3 by pulsed-laser deposition. The conductivity measurements performed along the c direction using LaNiO3 as the electrode show metallic behavior whereas they show semiconducting behavior in the a-b plane. Anisotropic transport property of these thin films is explained on the basis of nearly 180° connected Cu–O–Cu chains with an average Cu–O distance of 1.94 Å along the c direction and nearly 180° and 90° connected Cu–O–Cu chains in the a-b plane with short and long Cu–O distances ranging from 1.863 to 2.303 Å. YBa2Cu3O7−x has been grown along (00l) on La4BaCu5O13+δ and shows a Tc of 88 K.

Structural, optical, and electrical properties of bulk single crystals of InAsxSb(1-x) grown by rotatory Bridgman method

Radially-homogeneous and single-phase InAsxSb(1−x) crystals, up to 5.0 at. % As concentration, have been grown using the rotatory Bridgman method. Single crystallinity has been confirmed by x-ray and electron diffraction studies. Infrared transmission spectra show a continuous decrease in optical energy gap with the increase of arsenic content in InSb. The measured values of mobility and carrier density at room temperature (for x = .05) are 5.6×104 cm2/V s and 2.04×1016 cm−3, respectively.

Thermodynamic, kinetic and electrical switching studies on Si(15)Te(85-x)In(x) glasses: Observation of Boolchand intermediate phase

An interesting topic for quite some time is an intermediate phase observed in chalcogenide glasses, which is related to network connectivity and rigidity. This phenomenon is exhibited by Si-Te-In glasses also. It has been addressed here by carrying out detailed thermal investigations by using Alternating Differential Scanning Calorimetry technique. An effort has also been made to determine the stability of these glasses using the data obtained from different thermodynamic quantities and crystallization kinetics of these glasses. Electrical switching behavior by recording I-V characteristics and variation of switching voltages with indium composition have been studied in these glasses for phase change memory applications. (C) 2011 Elsevier Inc. All rights reserved.

Structural, thermal, and electrical properties of CrSi2

Stoichiometric CrSi2 was prepared by arc melting and compacted by uniaxial hot pressing for property measurements. The crystal structure of CrSi2 was investigated using the powder x-ray diffraction method. From the Rietveld refinement, the lattice parameters were found to be a = 4.427 57 (7) and c = 6.368 04 (11) Å, respectively. The thermal expansion measurement revealed an anisotropic expansion in the temperature range from room temperature 800 K with αa = 14.58×10−6/K, αc = 7.51×10−6/K, and αV = 12.05×10−6/K. The volumetric thermal expansion coefficient shows an anomalous decrease in the temperature range of 450–600 K. The measured electrical resistivity ρ and thermoelectric power S have similar trends with a maxima around 550 K. Thermal conductivity measurements show a monotonic decrease with increasing temperature from a room temperature value of 10 W m−1 K−1. The ZT values increase with temperature and have a maximum value of 0.18 in the temperature range studied. An analysis of the electronic band structure is provided.

Structural and electrical properties of low pressure metalorganic chemical vapor deposition grown Eu2O3 films on Si(100)

Structural and electrical properties of Eu2O3 films grown on Si(100) in 500–600 °C temperature range by low pressure metalorganic chemical vapor deposition are reported. As-grown films also possess the impurity Eu1−xO phase, which has been removed upon annealing in O2 ambient. Film’s morphology comprises uniform spherical mounds (40–60 nm). Electrical properties of the films, as examined by capacitance-voltage measurements, exhibit fixed oxide charges in the range of −1.5×1011 to −6.0×1010 cm−2 and dielectric constant in the range of 8–23. Annealing has resulted in drastic improvement of their electrical properties. Effect of oxygen nonstoichiometry on the film’s property is briefly discussed.

A Method of Evaluating Electrical Response of Solion Diodes

A method of evaluating the transient electrical response of a solion diode when excited by different current stimuli is given. This method is extended to obtain the transient response of the solion when connected in a circuit. To illustrate the utility of this method a circuit incorporating a solion diode has been analyzed.

Electrical Breakdown of Gases Between Coaxial Cylindrical Electrodes in Crossed Electric and Magnetic Fields

Sparking potentials have been measured in nitrogen and dry air between coaxial cylindrical electrodes for values of n = R2/R1 = approximately 1 to 30 (R1 = inner electrode radius, R2 = outer electrode radius) in the presence of crossed uniform magnetic fields. The magnetic flux density was varied from 0 to 3000 Gauss. It has been shown that the minimum sparking potentials in the presence of the crossed magnetic field can be evaluated on the basis of the equivalent pressure concept when the secondary ionization coefficient does not vary appreciably with B/p (B = magnetic flux density, p = gas pressure). The values of secondary ionization coefficients �¿B in nitrogen in crossed fields calculated from measured values of sparking potentials and Townsend ionization coefficients taken from the literature, have been reported. The calculated values of collision frequencies in nitrogen from minimum sparking potentials in crossed fields are found to increase with increasing B/p at constant E/pe (pe = equivalent pressure). Studies on the similarity relationship in crossed fields has shown that the similarity theorem is obeyed in dry air for both polarities of the central electrode in crossed fields.

Structural, electrical, and optical properties of as-grown and heat treated ultra-thin SnS films

The composition, structural, electrical, and optical properties of as-grown and heat treated tin-mono-sulfide (SnS) ultra-thin films have been studied. The ultra-thin SnS films were prepared on glass substrates by thermal resistive evaporation technique. All the SnS films contained nanocrystallites and exhibited p-type conductivity with a low Hall-mobility, <50 cm(2)/Vs. All these films are highly tin rich in nature and exhibited orthorhombic crystal structure. As compared to other films, the SnS films annealed at 300 degrees C showed a low electrical resistivity of similar to 36 Omega cm with an optical band gap of similar to 1.98 eV. The observed electrical and optical properties of all the films are discussed based on their composition and structural parameters. These nanocrystalline ultra-thin SnS films could be expected as a buffer layer for the development of tandem solar cell devices due to their low-resistivity and high absorbability with an optimum band gap. (C) 2011 Elsevier B.V. All rights reserved.

Effect of indium doping on the electrical switching behaviour of Ge–Te glasses

Bulk Ge15Te85−x In x (1 ≤ x ≤ 11) series of glasses have been found to exhibit a threshold switching behaviour for an input current of 2 mA. An initial decrease is seen in the switching voltages (V T) with the addition of indium, which is due to the higher metallicity of indium. An increase is seen in V T above 3 at.% of indium, which proceeds until 8 at.%, with a change in slope (lower to higher) seen around 7 at.%. Beyond x = 8, a reversal in trend is exhibited in the variation of V T, with a well-defined minimum around x = 9 at.%. Based on the composition dependence of V T, it is proposed that Ge15Te85−x In x glasses exhibit an extended rigidity percolation threshold. The composition, x = 3, at which the V T starts to increase and the composition, x = 7, at which a slope change is exhibited correspond to the onset and completion, respectively, of the extended stiffness transition. Thermal studies and photoconductivity measurements also support the idea of an extended rigidity percolation in Ge15Te85−x In x glasses. In addition, the minimum seen in V T at x = 9 is associated with the chemical threshold (CT) of this glassy system.