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Alternating current (AC) impedance measurements have been performed on 10- to 15- μm thick porous silicon layers on a (100) p-type silicon ( p(+)Si) substrate with the aluminium (Al) top electrode in a sandwich configuration in the range of 20 Hz-1 MHz and in the temperature ranging between 152 K and 292 K. The ac conductivity σ was found to increase with frequency f according to the universal power law: $$ \sigma_{\text{ac}} \, = \,\,Af^{s} $$ where the exponent s is a frequency and temperature-dependent quantity. A hopping process is found to be dominant at low temperatures and high frequencies, while a thermally activated free band process is responsible for conduction at higher temperatures. Capacitance is found to decrease with frequency but increase with temperature. Frequency dependence of the loss tangent is observed with a temperature-dependent minimum value. [ABSTRACT FROM AUTHOR]

The effect of various factors such as temperature, film thickness, and Pb content on the electrical conductivity and switching phenomenon in Se TePb films has been examined and is discussed herein. X-ray diffraction analysis and energy-dispersive x-ray spectroscopy were used to confirm the structure and chemical composition of the films, respectively. The variation of the electrical conductivity σ with Pb addition was correlated with the nature and strength of the Pb bonds in the SeTe matrix. Current-voltage characteristic curves showed two regions of high and low resistance with negative differential resistances, revealing memory-type switching corresponding to an electrothermal model. The applicability of this model was confirmed using the electrical to switching activation energy ratio, as well as the heat dissipation factor. The mean switching voltage was found to be dependent on temperature, film thickness, and composition. The decrease in the switching voltage with Pb addition is analyzed based on the thermal stability variation. [ABSTRACT FROM AUTHOR]

The in-plane thermal conductivity of semiconductor nanofilm is difficult to be tested due to suspension problem. The thermal boundary resistance (TBR) plays a key role in semiconductor nanoscale structures and nanoscale thermal experiments. By applying alternating current and direct current currents simultaneously on the semiconducting nanofilm on highly insulated substrate, multiharmonics including $$1\upomega $$ , $$2\upomega $$ and $$3\upomega $$ signals originating from the self-heating of nanofilm are measured. The thermal boundary resistance is introduced into the heat diffusion equation in in-plane direction. The expression of temperature oscillation and theoretical analysis of heat transport process show that the in-plane thermal conductivity and TBR can be decoupled from the multiharmonics in frequency domain. Thermal analysis justifies the multiharmonics method according to the effect of in-plane thermal conductivity, TBR between nanofilm and insulated substrate, resistance coefficient of semiconductor nanofilm on temperature oscillation at low frequency. Results show the multiharmonic method sensitivity variations depending on the TBR, the in-plane thermal conductivity, and the electric current frequency. [ABSTRACT FROM AUTHOR]

Complex oxides and semiconductors exhibit distinct yet complementary properties owing to their respective ionic and covalent natures. By electrically coupling complex oxides to traditional semiconductors within epitaxial heterostructures, enhanced or novel functionalities beyond those of the constituent materials can potentially be realized. Essential to electrically coupling complex oxides to semiconductors is control of the physical structure of the epitaxially grown oxide, as well as the electronic structure of the interface. Here we discuss how composition of the perovskite A- and B-site cations can be manipulated to control the physical and electronic structure of semiconductor—complex oxide heterostructures. Two prototypical heterostructures, Ba1−xSrxTiO3/Ge and SrZrxTi1−xO3/Ge, will be discussed. In the case of Ba1−xSrxTiO3/Ge, we discuss how strain can be engineered through A-site composition to enable the re-orientable ferroelectric polarization of the former to be coupled to carriers in the semiconductor. In the case of SrZrxTi1−xO3/Ge we discuss how B-site composition can be exploited to control the band offset at the interface. Analogous to heterojunctions between compound semiconducting materials, control of band offsets, i.e., band-gap engineering, provides a pathway to electrically couple complex oxides to semiconductors to realize a host of functionalities. [ABSTRACT FROM PUBLISHER]

A theoretical study is carried out of the possibility of effective second-harmonic generation in a metamaterial representing a structure of alternating layers of semiconductor material with intrinsic and metallic conductivity that can be grown by epitaxial methods. [ABSTRACT FROM AUTHOR]

The possibility of using substrates based on 'strained silicon on insulator' structures with a thin (25 nm) buried oxide layer for the growth of light-emitting SiGe structures is studied. It is shown that, in contrast to 'strained silicon on insulator' substrates with a thick (hundreds of nanometers) oxide layer, the temperature stability of substrates with a thin oxide is much lower. Methods for the chemical and thermal cleaning of the surface of such substrates, which make it possible to both retain the elastic stresses in the thin Si layer on the oxide and provide cleaning of the surface from contaminating impurities, are perfecte. It is demonstrated that it is possible to use the method of molecular-beam epitaxy to grow light-emitting SiGe structures of high crystalline quality on such substrates. [ABSTRACT FROM AUTHOR]

Analysis of thermal and electrical characteristics of the proposed device, selective buried oxide junctionless transistor (SELBOX-JLT) along with its analog performance, is compared with silicon on insulator junctionless transistor (SOI-JLT). The proposed device shows better thermal efficiency. The maximum device temperature of SELBOX-JLT is 311 K, much less than that of SOI-JLT (445 K). The proposed device has almost no effect of self-heating on output characteristics. SELBOX-JLT exhibits better I/ I ratio, subthreshold slope, and drain-induced barrier lowering as compared to SOI-JLT for the same channel length. The analog performance parameters as transconductance ( G), transconductance/drain current ratio ( G/ I), drain conductance ( G), output resistance ( R), intrinsic gain ( G R), and unity-gain frequency ( f) of the proposed device are found to be better than SOI-JLT. [ABSTRACT FROM AUTHOR]

Anisotropy, asymmetry, and other anomalies of electrical and thermal properties are revealed in CuInSe crystals. It is shown that the nature of these anomalies is associated with the natural coexistence of order and disorder in these ordered-defect compounds. [ABSTRACT FROM AUTHOR]

Thermal conductivity in non-metallic crystalline materials results from cumulative contributions of phonons that have a broad range of mean free paths. Here we use high frequency surface temperature modulation that generates non-diffusive phonon transport to probe the phonon mean free path spectra of GaAs, GaN, AlN, and 4H-SiC at temperatures near 80 K, 150 K, 300 K, and 400 K. We find that phonons with MFPs greater than 230 ± 120 nm, 1000 ± 200 nm, 2500 ± 800 nm, and 4200 ± 850 nm contribute 50% of the bulk thermal conductivity of GaAs, GaN, AlN, and 4H-SiC near room temperature. By non-dimensionalizing the data based on Umklapp scattering rates of phonons, we identified a universal phonon mean free path spectrum in small unit cell crystalline semiconductors at high temperature. [ABSTRACT FROM AUTHOR]

Polycrystalline samples of CaDyCoO ( x = 0.00, 0.02, 0.05, and 0.10) have been prepared by conventional solid-state synthesis. The x-ray diffraction (XRD) results revealed that all the samples are single phase. The thermoelectric properties were measured at 25 K to 300 K. The thermopower of all the samples was positive, indicating that the predominant carriers are holes over the entire temperature range. The electrical resistivity of all the samples exhibited the nonmetal-to-metal transition at below 75 K. The electrical resistivity decreased and the thermopower increased with increasing Dy content. Among all the samples, CaDyCoO had the highest dimensionless figure of merit of 0.044 at 300 K. [ABSTRACT FROM AUTHOR]

Electrospun carbon nanofibers (ECNs) were prepared through stabilization and carbonization of electrospun polyacrylonitrile nanofibers as the precursor, and their morphological, structural, and electrical properties were evaluated. Temperature dependencies of resistivity of ECNs carbonized at several temperatures were investigated. The character of the temperature dependencies of resistivity was typical for semiconducting materials. The values of corresponding activation energies were obtained for ECN samples carbonized at different temperatures, and the results showed that the activation energy of ECNs decreased with the increase of carbonization temperature. [ABSTRACT FROM AUTHOR]

Multigraphene films grown by sublimation on the surface of a semi-insulating 6 H-SiC substrate have been studied. It is shown that pregrowth annealing of the substrate in a quasiclosed growth cell improves the structural quality of a multigraphene film. Ohmic contacts to the film have been fabricated, and the Hall effect has been studied at low temperatures. It is found that a 2D electron gas exists in the films. It is concluded that the conductivity of the film is determined by defects existing within the graphene layer or at the interface between the graphene film and a SiC substrate. [ABSTRACT FROM AUTHOR]

Thin films of the semiconducting compound Mg2Ge were deposited by magnetron cosputtering from source targets of high-purity Mg and Ge onto glass substrates at temperatures Ts = 300°C to 700°C. X-ray diffraction shows that the Mg2Ge compound begins to form at a substrate temperature Ts ≈ 300°C. Films deposited at Ts = 400°C to 600°C are single-phase Mg2Ge and have strong x-ray peaks. At higher Ts the films tend to be dominated by a Ge-rich phase primarily due to the loss of magnesium vapor from the condensing film.␣At optimum deposition temperatures, 550°C to 600°C, films have an electrical conductivity σ600 K = 20 Ω−1 cm−1 to 40 Ω−1 cm−1 and a Seebeck coefficient α = 300 μV K−1 to 450 μV K−1 over a broad temperature range of 200 K to 600 K. [ABSTRACT FROM AUTHOR]

Abstract  The micro-Raman method is a noncontact and nondestructive method for thin film thermal conductivity measurements. To apply the micro-Raman method, however, the thickness of the film must be at least tens of micrometers. An analytical heat transfer model is presented in this work to extend the micro-Raman measurement method to measure the thermal conductivity of thin films with submicrometer- or nanometer-scale thickness. The model describes the heat transfer process in the thin film and substrate considering the effects of thin film thickness, interface thermal resistance, thermal conductivity of the thin film and substrate. From this heat transfer model, an analytical expression for the thermal conductivity of the thin film is derived. Experiments were successfully performed to measure the thermal conductivity of 200, 300 and 500 nm thickness silicon dioxide films using the extended micro-Raman measurement method, with results confirming the accuracy and validity of the extended model. [ABSTRACT FROM AUTHOR]

In this study novel metal coordination polymers were synthesized such as poly-4,4′-oxybis[N-(3,4-dihydroxybenzilidene)aniline] (P-3,4-HBA) containing Cu, Co, Pb, Ni, Zn, Cd, Cr, Mn and Zr metals in the polymer backbone. The polymers are abbreviated as P-3,4-HBA-Cu, P-3,4-HBA-Co, P-3,4-HBA-Pb, P-3,4-HBA-Ni, P-3,4-HBA-Zn, P-3,4-HBA-Cd, P-3,4-HBA-Cr, P-3,4-HBA-Mn and P-3,4-HBA-Zr, respectively. To confirm the structures FT-IR, UV-vis, H and C-NMR spectral techniques were used. Additional characterization of the polymers was made by size exclusion chromatography (SEC), TGA-DTA and solubility tests. By TGA analysis, P-3,4-HBA-Zr was the most stable polymer against thermal degradation among those synthesized. In addition, it was found that, with exception of P-3,4-HBA-Cr, the other synthesized polymers have little solubility in many organic solvents and water. According to SEC results, P-3,4-HBA-Cr has a single fraction containing 21-22 mer units. Electrical conductivities of the monomer and polymers were measured by the four-point probe technique. The polymers were semiconductors; and, some of their conductivities can be increased via doping with iodine. According to the electrical conductivities of the undoped P-3,4-HBA-Cr and P-3,4-HBA-Zr polymers have nearly ten-times higher conductivities in comparison to the others. From UV-vis measurements, the optical band gaps ( E ) of 3,4-HBA and P-3,4-HBA-Cr were 2.58 and 2.39 eV, respectively. This result indicates that P-3,4-HBA-Cr has a lower band gap and consequently higher electrical conductivity than 3,4-HBA. Thus, with good solubility, high electrical conductivity and high thermal stability P-3,4-HBA-Cr may be considered as the most useful metal coordination polymer among those synthesized. [ABSTRACT FROM AUTHOR]

Results of studies of electrical properties of structures including metal-conducting oxide (ITO), and β-ZnP2 semiconductor of n-type conductivity are reported. It is established that the total resistance of the structures under study is determined by deep levels of intrinsic defects in the band gap of semiconductor. Long-term relaxation of capacitance and conductivity is observed after switching off the reverse bias at low temperatures, which is associated with restoration of the nonequilibrium charge in the space-charge region. Models of processes in which experimental results are interpreted satisfactorily are constructed. [ABSTRACT FROM AUTHOR]

Results of studies of electrical properties of structures including metal-conducting oxide (ITO), and β-ZnP2 semiconductor of n-type conductivity are reported. It is established that the total resistance of the structures under study is determined by deep levels of intrinsic defects in the band gap of semiconductor. Long-term relaxation of capacitance and conductivity is observed after switching off the reverse bias at low temperatures, which is associated with restoration of the nonequilibrium charge in the space-charge region. Models of processes in which experimental results are interpreted satisfactorily are constructed. [ABSTRACT FROM AUTHOR]

Abstract  A new curvature-correction technique for improving the temperature behavior of a CMOS voltage reference will be presented. The reducing of the temperature coefficient for the reference voltage will be realized compensating the nonlinear temperature dependence of the gate-source voltage for a MOS transistor working in weak inversion with the difference between two gate-source voltages. These MOS transistors are biased at drain currents with different temperature dependencies (PTAT and PTAT α, respectively), α parameter being selected to the optimal value for the implementing technology. The PTAT voltage generator will be designed using an original Offset Voltage Follower block, with the advantage of a reduced silicon occupied area as a result of replacing classical resistors by MOS active devices. SPICE simulation reports TC = 1.95 ppm/K for an extended temperature range, 273 K T  [ABSTRACT FROM AUTHOR]

The thermovoltaic effect in the semiconductor rare-earth compound samarium sulfide (SmS) is briefly described. The qualitative dynamic model of the effect for explaining the possibility of the long-term electric voltage generation on the basis of the thermovoltaic effect is proposed. The model uses a combination of thermal and electronic processes. [ABSTRACT FROM AUTHOR]

The critical superconductivity field H is measured on lead single crystals. It is shown that the temperature dependence of H/ H in the vicinity of superconducting transition temperature T is essentially nonlinear. Relative changes in the value of H/ H reach approximately 30%, which cannot be described by the Ginzburg-Landau theory. The experimental temperature dependences lead to the conclusion that the surface superconducting transition temperature noticeably exceeds the superconducting transition temperature in the bulk of the semiconductor. The differences in the critical temperatures and in the Ginzburg-Landau parameters for lead are estimated. [ABSTRACT FROM AUTHOR]

Temperature stresses in semiconductor barium-titanate-based ceramics with a layer structure under the action of current loads have been investigated by numerical methods. It has been shown that by optimizing the thickness ratios between the layers and their properties one can markedly decrease the maximum stresses compared to homogeneous thermistors. [ABSTRACT FROM AUTHOR]

Ta-Si-N ternary barrier films were obtained by reactive rf magnetron sputtering of a Ta5Si3 target in an Ar-N2 gas discharge. The films were tested as diffusion barriers between Au and GaN layers. The efficiency of these films as diffusion-suppressing barriers is determined by transmission electron microscopy, secondary-ion mass spectroscopy, and X-ray diffraction analysis. It is shown that the diffusion barrier with optimized properties (Ta34Si25N41) in an Au/GaN metallization system can be used to advantage at temperatures above 800°C. A correlation between the composition, microstructure, resistivity, thermal stability, and diffusion-suppressing properties of the films is discussed. [ABSTRACT FROM AUTHOR]

CdSSe nanobelts (NBs) are synthesized by thermal evaporation and then characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), transmission electron microscopy (TEM), high-resolution electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS), photoluminescence (PL), and cathodoluminescence (CL). It is found that the CdSSe NBs have a good morphology and microstructure without defects. CL is sensitive to the defects of CdSSe NBs; thus, we can select single nanobelt with homogeneous CL emission to prepare a detector. Based on it, the photodetector of single CdSSe NB was developed and its photoelectric properties were investigated in detail. It is found that under illumination of white light and at the bias voltage of 1 V, the photocurrent of a single CdSSe nanobelt device is 1.60 × 10−7 A, the dark current is 1.96 × 10−10 A, and the ratio of light current to dark one is 816. In addition, the CdSSe nanobelt detector has high photoelectric performance with spectral responsivity of 10.4 AW−1 and external quantum efficiency (EQE) of 19.1%. Its rise/decay time is about 1.62/4.70 ms. This work offers a novel strategy for design wavelength-controlled photodetectors by adjusting their compositions. [ABSTRACT FROM AUTHOR]