In the present work the technique of the high-pressure thermoelectric (TE) investigation has been developed for the phase transition recording at Si and the values of thermopower (S) for the different high pressure and metastable phases of Si have been obtained using the automated high-pressure set-up. The TE properties of various phases and states of Si were established which may be potentially used in Si-based nano-devices [1, 2]. The technique was shown also to be sensitive to the pre-treatments applied to a sample including annealing, doping, and irradiation by high-energy particles. The band structure calculations of the several phases of Si were carried out using linear muffin-tin orbital method (LMTO). The experimental values of thermoelectric power of various phases of Si up to 25 GPa are compared with the theoretical estimations basing on the band structure calculations performed. The theoretical calculations have confirmed the principal role of the contribution of d-band both in the forming of the electron states in the vicinity of Fermi level, as well as in the positive sign and the value of a thermoelectric power.
The recent progress in creation of materials with negative refractive index inaccessible for natural substances show
all-important role of the multi-phase materials in modern technology. In the present work the approach for calculating of
effective properties is considered for multi-component composite materials with variable configurations and
concentration of inclusions [1]. The approach is based on interpolation formulas obtained between the rigorously
calculated limiting borders [2]. The general merit of the model is the ability to obtain algebraic formulas for complicated
properties with the vectors of electrical, thermal, magnetic, etc. fields directed along the different axes [3]. The examples
of application of the above model are given for the analysis of multi-phase states in the vicinity of pressure-induced
phase transition. The model was used for a set of semiconductor compounds like PbX, SmX (X - Te, Se, S), iron ore, etc.
[4]. The program for calculation of different electrical, thermal, mechanical etc. properties of n-phase systems with
variety of configuration and concentration of phase inclusions has been created, which may be applicable for real multiphase
systems.
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.
The work was partly supported by the Russian Foundation for Basic Research (RFBR), Gr. No. 01 - 02 - 17203.
The technique for investigation of thermoelectric, galvanomagnetic and thermomagnetic effects at ultrahigh pressure (up to 30 GPa) is presented. For micro-samples of chalcogens (Te,Se,S) and chalcogenides (n-PbTe,p-PbSe,p-PbS) the thermoelectric power, magnetoresistance and longitudinal and transverse Nernst-Ettingshausen effects have been measured. The systematical comparison of various effects in different materials are done. Effects obtained allowed to estimate the scattering parameter and mobility of charge carriers. It was shown the advantages of thermomagnetic technique over galvanomagnetic ones. Thus, from thermomagnetic effects the gapless state of materials was observed for the first time at room temperatures. The technique developed seems to be perspective for using in micro-device technology and thermosense industry. The work was supported by the Russian Foundation for Basic Research, Gr. No. 01-02-17203.
Lead chalcogenides are successfully applied at sensors of infrared radiation, thermoelectrical devices, thermogenerator, photoresistances, photodiodes, lasers, tensometers etc. Under high pressures above 2.5 - 6 GPa lead chaclogenides are known to suffer phase transitions, but up to now the thermoelectric properties of these materials at high pressure were unknown. In recent papers it was shown that heterophase state of material, which is being forming in the vicinity of semiconductor-metal phase transformations may be considered as a model of layer fabricated systems. As the most properties being dependent on the concentration and configuration of phases inclusions these materials may be used in engineering. For example, semiconductor-metal phase transitions induced by nanosecond heating and cooling of small regions of the memory cell are known to be using for nonvolatile memory develop. Recently the new technique of thermomagnetic measurements allowing to test a micro-samples of semiconductors have been developed at high pressure up to 30 GPa. The technique was applied for determination of scattering mechanisms and mobilities of charge carriers of direct-gap semiconductors Te, Se at ultrahigh pressure up to 30 GPa. The above measurements seems to be perspective for implementation to microelectronic manufacturing and MEMS technologies, for example, in modeling, quality control or testing of integrated circuit (IC). In present paper the thermo- and galvanomagnetic properties of micro-samples ~ 200×200×20 mkm of lead chalcogenides (PbS, PbSe, PbTe) at high pressure are investigated. The data of transverse magnetoresistance (MR) and also transverse and longitudinal Nernst-Ettingshausen (N-E) effects of lead chalcogenides both for initial and new phases, and also for heterophase states in the vicinity of phase transformations at high pressure are presented. One may suppose that the effects observed will find an interesting applications in thermosense industry. The work is supported by the Russian Foundation for Basic Research, Gr. No. 01-02-17203.
In present paper the longitudinal and transverse thermomagnetic Nernst-Ettingshausen effects and also magnetoresistance were investigated at high pressure chambers with sintered diamond anvils near semiconductor-metal transition points. Chalcogens (Te, Se) and chalcogenides (PbS, PbSe, PbTe) semiconductor micro-samples have been chosen as an objects for experimental study. The calculations of thermo- and galvanomagnetic properties of heterophase materials as a function of inclusion concentration and configuration were performed in the model of the oriented inclusions model with variable phase configuration. Both the approach and experimental technique developed seems to be perspective for using in micro-device technology for quality control and advanced semiconductor manufacturing.
The work was supported by the Russian Foundation for Basic Research (RFBR), Gr.No.01-02-17203.
At ultrahigh pressure the thermoelectric power, magneto resistance, and thermo magnetic effects were measured for Te, Se and S samples in the vicinity of semiconductor-metal phase boundary. The significant longitudinal and transverse Nernst-Ettingshausen effects observed for Te and Se allowed to estimate the scattering parameter for charge carriers. The increase of holes mobility obtained from longitudinal and transverse Nernst-Ettinghausen effects being consistent with growth of magneto resistance under pressure. These experiments gave configuration to decreasing of effective mass of holes at closing of direct semiconductor gap. From thermoelectric power measurements up to 40 GPa Sulfur was found to be a narrow-gap semiconductor with large negative pressure coefficient of electron gap. Negative magneto resistance effect observed in S suggests very low mobility of holes, that is in well agreement with retaining molecular type of crystal structure. Thermo magnetic effects, like galvanomagnetic ones, seems to be perspective for using in micro-device technology.
New results of high pressure investigations of semiconductor compounds PbX (X-S, Se, Te) and novel data of thermoelectric power S of high pressure phases are presented. In vicinity of metal-semiconductor phase transformations at high pressure P above approximately 2.5, 4.5 and 6.5 GPa, respectively, where samples became a mixture of phase inclusions, disproportional variations of electrical resistance and S were observed. Analysis of properties changing was made by using of oriented inclusions model with variable phase configuration. The using of high pressure set up with sintered diamond plungers made it possible to investigate as electronic and also configuration parameters of phases for heterophase systems at high pressures.
The technique of investigations of resistance (rho) , thermoelectric power S, and galvanomagnetic properties of materials by the two-terminal method of measurements under pressure up to 30 GPa is discussed. The combine of stationary and nonstationary regimes of treatment, variation of high pressure chambers with conducting or insulating plungers and using of simultaneous and parallel measurements of various properties are proposed to estimate the parameters of materials under testing. The results of investigations of initial semiconductor and high pressure metal phases of Ge, Te, and molecular solid-Iodine up to 30 GPa at the diamond- plungers apparatus are represented. The technique may be useful for semiconductor fabricated device treatment.
Magnetoresistance (MR) measurements are known to be used for the determination of electron density and mobility in bulk semiconductors and also in a wide variety of multi-layers fabricated devices. By use of the synthetic diamond plungers MR of high pressure phases have been measured for Mercury, Cadmium and Zinc Chalcogenides etc. up to 30 GPa. At pressure- induced phase transformations in some materials (HgSe, HgTe, HgO, CdTe) the inversions of MR sign were observed due to electron structure reconstruction and changing the electron scattering mechanisms. In the vicinity of the phase boundary MR effect was sufficient to the content of phase inclusions, so HgSe, HgCdSe and HgSeS crystals had unusual electrical and galvanomagnetic properties at high pressures. The aim of the present paper is to investigate the influence of phase inclusions on the Hall effect, MR, value of resistivity (rho) and its temperature dependence.
The influence of Metal (M) and Semiconductor (SC) inclusions on magnetoresistance (MR), Hall effect R and temperature dependence of resistivity (rho) (T) of heterophase materials is investigated for a case, when the signs of magnetoresistance effects for these phases are opposite. According to model used the relative position of signs inversion borders for MR and temperature coefficient of (rho) (T) in coordinates resistivity - phase concentration ought to be independent on configuration of inclusions. For HgSe1-xSx crystals in the vicinity of pressure- induced structural phase transition the result of calculations coincide with the experimented data of MR and (rho) (T).
The diamond-plungers apparatus for simultaneous measurements of resistance (rho) , thermoelectric power S, volume V of samples is described. The apparatus contains the microcontroller for the operation by the measurements and keeping the experimental data. The examples, comprised S, (rho) , V recording for semiconductors Ge, Si and HgTeS in pressure range 0 - 30 GPa are represented.
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