Молекулярно-динамическое исследование влияния концентрации вакансий на скорость миграции границ наклона в никеле

The influence of vacancy concentration on the migration rate of high-angle tilt boundaries with misorientation axes <111> and <100> in nickel was studied by the method of molecular dynamics. It is shown that the dependence of the migration rate on the concentration of vacancies introduced at the initial stage of modeling has a maximum near 1%. The decrease in the migration rate with a further increase in the free volume is mainly due to the deceleration of the boundary by low-mobile vacancy clusters, which at high vacancy concentrations the boundary is no longer capable of sorbing. The second reason for the decrease in the migration rate with an increase in the concentration of vacancies above 1% is a decrease in the surface tension of grain boundaries and, accordingly, the driving force of their migration due to the finite sorption capacity of the boundaries with respect to the excess free volume.

Mechanism of Enhanced Hydrogen Diffusion in Solar Cell Silicon

ABSTRACTExperimental results that support our previously reported observations of enhanced diffusivity of hydrogen in some solar cell silicon are presented. The diffusivities of hydrogen, implanted at low energies, were measured for several commercial silicon substrates. It is shown that the diffusivity of hydrogen in some solar cell substrates is about two orders of magnitude higher than that in Float Zone silicon in a temperature range of 100° - 300°C. This value of diffusivity is also close to that observed along some grain boundaries in polycrystalline silicon. It is determined that hydrogen in-diffusion is accompanied by an out-diffusion of boron, and that the hydrogen diffusivity is retarded by high concentrations of oxygen. A mechanism for enhanced hydrogen diffusion is proposed which invokes formation of a highly mobile vacancy-hydrogen complex.