Pressure and Stress Effects on Diffusion in Si

Abstract

The thermodynamics of diffusion under hydrostatic pressure and nonhydrostatic stress is presented for single crystals free of extended defects. The thermodynamic relationships obtained permit the direct comparison of hydrostatic and biaxial stress experiments and of atomistic calculations under hydrostatic stress for any proposed mechanism. Atomistic calculations of the volume changes upon point defect formation and migration, and experiments on the effects of pressure and stress on the diffusivity, are reviewed. For Sb in Si, using as input the results of ab initio calculations of the effect of hydrostatic pressure on diffusion by the vacancy mechanism, the thermodynamic relationships successfully account for the measured effect of biaxial stress on diffusion with no free parameters. For other cases, missing parameters are enumerated and experimental and calculational procedures outlined.

Stress induced crystallization of hydrogenated amorphous silicon

“…It is worthwhile to note that while experimental evidence exists for biaxial stress enhanced crystallization [32], and diffusion [33], theoretical understandings are not completely resolved relative to the hydrostatic case [34].…”

Comparative analysis of the thermoelectric properties of the non-textured and textured Bi1.9Gd0.1Te3 compounds

“…At the SPS-process, stages of compacting and sintering are implemented simultaneously at high temperatures under simultaneous acting both uniaxial pressuring and pulse electrical current. Extra mechanisms of an interstitial diffusion can be involved in densification process for the SPS-sample, which are based on electrical diffusion and reducing the diffusion constant under the applied SPS-pressuring [61][62][63][64][65][66][67]. These mechanisms will result in higher densification of the SPS-sample as compared to that of the CIP-sample.…”

Investigation of oxygen self-diffusion in PuO2 by combining molecular dynamics with thermodynamic calculations

“…20,55 Recalling that the activation volume corresponds to the isothermal volume change of the crystal due to the formation and migration of a defect, we expect that, in the case of an oxygen vacancy formation that is accompanied by an outward relaxation, due to the electrostatic repulsive forces between the adjacent Pu cations, the increase of temperature (at ambient pressure) should result in an increment of the volume available to the vacancy, due to the lattice thermal expansion. 43 Taking into account that the volume change between the equilibrium state and the excited state at the saddle-point (migration volume) contributes further to the total change of activation volume, the thermal expansion coefficient of ߭ ௧ is expected to increase more than that of the crystal. Consequently, the compressibility of the activation volume which is related to the vacancies should also increase.…”

“…Furthermore, the value and sign of the activation volume (refer to eqn ( 5)) is important in order to distinguish the kind of the diffusion mechanism, i.e., vacancies or self-interstitials. 43 In order to estimate all the previous point defect parameters by means of the cBΩ model (see eqns ( 3)-( 7)), the constant c act should be determined. In principle, ܿ ௧ equals to ℎ ௧ ‫ܤ/‬ Ω where the subscript refers to T = 0 K, since according to eqn (4), 20 The calculation of ܿ ௧ can be also achieved in different ways, based on the available experimental diffusion data.…”