Electronic properties of multi-phase systems with varying configuration of inclusions

ABSTRACT Multi-component systems (heterophases, layered, porous, misfit, composite) present the interest for different spheres of science and engineering. The paper covers both theoretical and experimental investigations of such systems with varying concentration and configuration of inclusions. En equations describing the dependence of electronic properties (thermomagnetic and galvanomagnetic as well as electrical and thermoelectric ones) of such systems on concentration and configuration of inclusions are presented. The equations derived may be used for analysis of electronic properties of advanced heterostructures. The above model describing the dependence of electronic properties of multi-component heterophase systems on concentration and configurations of inclusions allows to point out the ways for improving of electronic properties (thermoelectric effectiveness, thermoelectric and thermomagnetic figure of merit, etc.) and for extending of functional possibilities of such systems. So, the approach offered may be used for optimization of properties and for design of microdevices with improved characteristics

Thermoelectric properties and phase transitions of II-VI semiconductors at high pressure

The high-pressure phase transitions in II -VI semiconductors (HgTe, HgSe, HgS, HgO, CdTe, CdSe, CdS, ZnTe, ZnSe, ZnS, ZnO) are analyzed in light of recent findings. A contribution is emphasized of the thermoelectric power (Seebeck effect) technique to registration of new electronic phases and to prediction of their related structural modifications. A novel thermopower study of ZnX (X -Te, Se, S) revealed a difference between the high-pressure NaCl phases of ZnSe and ZnS and the orthorhombic Cmcm phase of ZnTe. Mechanisms of the pressure-induced transitions in ZnX and other II -VI compounds are discussed

Thermo-and galvanomagnetic technique for semiconductors testing at high pressure up to 30 GPa

Abstract The thermoelectric power (S), magnetoresistance (MR) and thermomagnetic (TM) e ects were measured at high pressure (P) in the vicinity of semiconductor-metal phase transitions for Te, Se and S micro-samples. From longitudinal and transverse Nernst-Ettingshausen (N-E) e ects for Te and Se, the scattering parameter (r) of holes was estimated and under the closing of semiconductor gap (Eg) the decreasing of their e ective mass (m) was found. S of Sulphur also decreased with pressure up to 40 GPa and the negative MR e ect observed indicates low mobility ( ) of holes. The technique developed seems to be suitable for use in micro-device technology.

Raman spectra of lead chalcogenide single crystals

Raman spectra of single crystals of lead chalcogenides (PbTe, PbSe, PbS) were studied at room temperature and ambient pressure. The structure of spectra for all compounds is rather similar showing the bands in one-and two-phonon range. Possible spectra identification is discussed

Pressure-induced phase transitions in Si observed by thermoelectric power measurements

Abstract For the first time the phase transitions under high pressure P up to 20 GPa have been observed in Czochralski-grown Si single crystals by thermoelectric power S measurements. Values of SzC8G3 mV/K have been determined for tetragonal, orthorhombic and simple hexagonal high-pressure phases. The behaviour of S(P) was found to be rather different for different Si samples-initial and pre-treated by high temperatures 450-650 8C under hydrostatic pressure 0-1.5 GPa

Translated from Pis'ma v Zhurnal Éksperimental'no oe i

The parameters of electronic structure of semiconductors, including estimates for the effective mass of charge carriers m , are commonly studied by measuring optical properties or galvanomagnetic effects, which are determined by the mobility of electrons and holes The goal of this work was to develop a procedure of thermomagnetic investigations at ultrahigh pressures. Semiconductors in which the mobility and, hence, the effective mass of charge carriers strongly vary with pressure are most interesting objects for such measurements. For the majority of known semiconductors, the effective mass of carriers m is proportional to the band gap width E g , which corresponds to the general theoretical notions of the band theory A high pressure up to 30 GPa was created with the use of chambers of synthetic superhard materials (diamond, boron nitride

High-Pressure Treatment up to 25~GPa of Czochralski Grown Si Samples Containing Different Admixtures and Defects

The thermoelectric properties of a set of single crystalline Si wafers with different oxygen concentration grown by the Czochralski technique have been studied at ultrahigh pressures up to 25 GPa. The dependence of semiconductor-metal transition pressure at Czochralski grown Si on the concentration $c_{O}$ of the interstitial oxygen was found to present a convex curve with the maximum near $c_{O} \approx 9 \times 10^{17} cm^{-3}$. The high pressure thermoelectric power method seems to be suitable for characterization of impurity-defect structure of Si wafers. For $Si_{1 - x}Ge_{x}$ crystals (1% < x < 3%) the strong changes of both the value and the sign of thermoelectric power have been observed at pressures much less than ones of Si-I → Si-II transition. From nanoindentation data the phase transition Si-I → Si-II, corresponding to semiconductor-metal electronic transformation has been detected at the loading up to ≈ 10 mN. These findings suggest a way for creation of integrated circuits, in which zones with different types of conductivity and hence different p-n, p-n-p etc. structures may be "written" by applied stress at nanoscale level, and the control on the value of the above stresses now is possible by the proposed nanoindentation technique