高压下锐钛矿TiO2的电阻率及能带结构的研究

应用在位电阻率测量方法研究高压下锐钛矿TiO2的电学性质。通过研究电阻率随压力变化的异常变化点,观察到了TiO2从锐钛矿－柯铁矿－斜锆石的相变。卸压后,电阻率数值和初始值相差2个数量级,说明该相变为不可逆相变。结合第一性原理计算结果表明,柯铁矿结构更小的带隙是导致TiO2电阻率减小的根本原因。     

高压下锐钛矿TiO2的电阻率及能带结构的研究

应用在位电阻率测量方法研究高压下锐钛矿TiO2的电学性质. 通过研究电阻率随压力变化的异常变化点, 观察到了TiO2从锐钛矿-柯铁矿-斜锆石的相变. 卸压后,电阻率和初始值相差2个数量级, 说明该相变为不可逆相变. 结合第一性原理计算结果表明, 柯铁矿结构更小的带隙是导致TiO2电阻率减小的根本原因.     

Pressure dependence electrical resistivity in DVT grown molybdenum dichalcogenides

Abstract

Single crystals of MoS _x Se_2?x (x=0, 1, 2) have been grown by direct vapour transport method. Pressure-dependent d.c. electrical resistivity measurements have been carried out on the grown crystals to check the possibility of phase transition up to 8 GPa. However, no such transition is observed in the present case but a decrease in resistivity is found with increase in pressure. The observed results have been analysed and discussed on the basis of band structure.     

Pressure dependence of the resistivity of zinc oxide

The change of resistivity of n-type ZnO with hydrostatic pressure has been found to be 2.2 × 10^?6/kg cm^?2 and is nearly linear for pressures up to 28000 kg/cm². This result can be shown to be incompatible with a simple model of electron mobility which assumes that the scattering due to acoustic modes arises from a deformation potential associated with lattice dilatation.     

Temperature dependence of the electrical resistivity in amorphous metals

In amorphous metals the electrical resistivity increases linearly in the temperature range from 2 to 40 K. This result differs fundamentally from the nonlinear behaviour known for crystalline metals and it suggests the conduction electrons not to be scattered by the vibrations of the amorphous point lattice. The temperature dependent part of the resistivity in amorphous metals is explained with scattering of conduction electrons by fluctuations ofp-electrons.     

Pressure dependence of the resistivity of several amorphous alloys

Measurements under hydrostatic pressure of the electrical resistance of a series of metglas alloys and one alloy of NiY have been made in the range 0–5 kbar and 77–300 K. In general the behaviour fits no general pattern, except that Metglas 2204 (BeTiZr) obeys a simple prediction of the Ziman model as found by Nagel for thermopower.     

The temperature dependence of the electrical resistivity of gold films

An analysis is presented of resistivity data on thin gold films with a view to characterizing any surface-caused quadratic temperature dependence (T²) to the resistivity. No evidence is found for a T² term varying in magnitude according to the inverse sample thickness. This is in accord with other studies on gold foils and disagrees with a recent suggestion that surface scattering causes a T² contribution to the resistivity of the noble metals.     

Free energy and electrical resistivity of molten alloys

The free energies of mixing for molten indium-antimony, cadmium-antimony, indium-bismuth, lead-bismuth and tin-bismuth were calculated from the variation of electrical resistivity with composition employing the model of Takeuchi and Endo. Resistivities measured in this laboratory with an electrodeless technique for In-Sb alloys, together with published values for Cd-Sb, In-Bi, Pb-Bi and Sn-Bi alloys were used in the calculations.

Evaluation of the resistivity data gave the composition dependence of the derivatives of the chemical potentials of the constituents and the integral molar free energies of mixing. No assumptions regarding ideal entropy were made to obtain these free energy values although a statistically random mixture of ions is presumed in the scattering model.

Conclusions drawn from a comparison between the calculated free energy values and published thermodynamic data for these systems are discussed in terms of departures from regularity and the variations in the effective free electron concentration.     

Pressure dependence of the band-gap energy and the conduction-band mass for an n-type InGaAs/GaAs strained single-quantum well

We report the measurement of the pressure dependence for the band-gap energy and conduction-band mass for an 80 Å-wide n-type strained-single-quantum well at 4.2 K for pressures between 0 and 35 kbar and fields up to 30 T. The band-gap energy , at each pressure, was determined by extrapolating the magnetoluminescence “fan-diagram” to zero magnetic field. The pressure dependence of the band-gap energy was found to be quadratic with a linear term of about 10.3 meV/kbar and a small, , quadratic contribution. Analyses of the pressure-dependent 4.2 K magnetoluminescence data yield a conduction-band mass logarithmic pressure derivative

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The temperature dependence of the electrical resistivity of granular metals

A simple percolation model of the hopping conduction in granular metals is proposed. The separation between the grains, in this model, is a random variable uncorrelated with the activation energy, the latter being dominated by the intragrain level splitting. The model is capable of reproducing the resistivity exp $\text{(}\text{T}{}_0\text{T}\text{)}{}^{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}$ law over a wide temperature range, in spite of the narrow range of the grain diameters, explaining the recent observations of Choi et al.     

Temperature dependence of the electrical resistivity of amorphous Pd-Si alloy

Czechoslovak Journal of Physics - The temperature dependence of the electrical resistivity of amorphous binary Pd-Si alloy has been calculated by means of the t-matrix formulation of the extended...     

Pressure dependence study of the effective mass in Ga0.47In0.53As/InP heterojunctions

A study of the effective mass in GaInAs/InP heterojunctions under hydrostatic pressure up to 15 kbars is presented. Earlier results have shown the importance of hydrostatic pressure effects on the band parameters of the heterojunction to explain the experimental decrease of the carrier concentration with pressure at the interface (1). Here magnetophonon resonance experiments are performed to work out the increase of mass with pressure in our samples. The effective mass at atmospheric pressure is deduced from high temperature cyclotron resonance experiments and then used to calculate the frequency of the phonon interacting with the 2D electron gas (w_o). The value of w_o is found to be dependent on the carrier concentration of the measured samples. The lowest value is found for the highest carrier concentration sample.A band edge effective mass increase of 1 ± .1% kbar is found in the highest carrier concentration sample. This is two times smaller than the rate found experimentally in GaInAs bulk material and slightly smaller than in an AlInAs/GaInAs heterojunction. The experimental increase could be fitted with multiband k.p theory assuming no pressure dependence for the conduction band-valence band matrix element E_p. However at lower concentration a variation of the matrix element E_p with pressure has to be considered.     

Temperature dependence of the electrical resistivity of the nickel-platinum alloy system

The temperature dependence of the electrical resistivity of Ni_1?xPt_x (x = 1, 2, 3, 4, 5, 8, 10, 15, 20, 25 and 30 at.%) between 77 and 700 K has been investigated. The experimental results are interpreted according to the theoretical model developed by Mott. It is shown that for this system Matthiessen's rule is not obeyed.     

On the temperature dependence of the electrical resistivity of non-stoichiometric actinide compounds

We suggest that the systematic investigation of the dependence of resistivity upon temperature in non-stoichiometric actinide compounds could bring some information on the possibility of non-Kondo minima in highly resistive systems suggested by a recent theory of Markowitz.     

On the anomalous temperature dependence of the electrical resistivity in liquid alloys

It is demonstrated that the anomalous temperature dependence of the electrical resistivity, as experimentally reported for liquid binary alloys of simple metals, arises primarily from the significant decrease in the partial localization of the valence electrons on the electronegative component.     

Note on measurements of the electrical resistivity of CrMn alloys

Various experimental results on CrMn alloys are reviewed in order to discuss recent precise measurements of the electrical resistivity in the vicinity of the spin ordering transition temperature T_N. Different critical exponents λ have been observed for the electrical resistivity temperature derivate in alloys of similar composition. Apparent discepancies arte interpreted following recent theoretical work.     

Pressure dependence of the electrical resistivity of Ag(Mn), both in the dilute limit and in the spin glass regime

The electrical resistivity of the dilute spin glass alloys Ag(1,540 ppm Mn) and Ag(1,015 ppm Mn) has been measured from 1.3–30 K at pressures up to 70 kbars. The temperature of the resistance maximum,T _m , is found to shift to higher temperatures, this shift being stronger for the more concentrated alloys.Additionally an Ag(20 ppm Mn) Kondo-alloy has been investigated. Application of pressure causes an increase of the Kondo temperatureT _K from which the volume dependence of the effective exchange constantJ is derived.With this information theT _m -shift in the spin glass alloys can be understood in a qualitative and quantitative manner within Larsen's model.