539.3/.6
53.091

стійкість
питома електропровідність
деформаційні ефекти
resistance
electrical conductivity
deformation effects

На основі теорії опору матеріалів для різних кристалографічних напрямків розраховано залежність критичної механічної напруги від площі поперечного перерізу зразків n-Ge, що використовуються при дослідженнях деформаційних ефектів при високих одновісних тисках. Визначено оптимальні параметри форми даних зразків. Оцінено вплив геометричних розмірів зразків на точність вимірювання питомої електропровідності монокристалів n-Ge для монокристалів із низьким, середнім та високим рівнем легування.
Based on the theory of strength of materials dependence of the critical mechanical stress on the cross-section and shape of samples n-Ge, which used in research of deformation effects under high uniaxial pressures are obtained. The analytical expressions for the first critical mechanical stress for n-Ge samples for measurement of piezoresistance, using the solution of the problem for the Euler for elastically deformed rod, are obtained. The critical stress for the case of rigidly fixed ends of rod is calculated. The dependences of the critical stress on the cross-section of sample for rectangular parallelepiped form and dumbbell form of sample are obtained. We considered the cases of uniaxial pressure in crystallographic directions [100], [110] and [111]. Take into account dependences of critical mechanical stress on the cross-section of samples for different shapes and parameters measurement setup for study deformation effects the optimal size and shape for these samples are determinate. To achieve maximum stability samples, the minimal permissible length of the sample and the maximum value of the cross-section are defined. The minimal length of the investigated samples was determined because of specificity of samples preparation and parameters of measurement setup. So for dumbbell form of sample allowable length is equal to 3 mm, and rectangular parallelepiped form - 4 mm. The maximum allowable dimensions of cross-sectional of the sample is dependent on the maximum pressure force that can develop measuring setup for get some pressure . In this case, defined dimensions of cross-section of samples to achieve a pressure P=2·109 Pa. The question of the influence of low-current electrodes on the measured value of conductivity in the case of a weak magnetic field are discussed. The effect of geometrical dimensions of samples for precision measurement of conductivity of single crystals of n-Ge with low, medium and high levels of doping are estimated.