Defect formation in tellurium in various gravity conditions
Abstract
The effect of gravity (from micro-to a rather high gravity, 5g0) acting during tellurium crystallization on the concentration of neutral (ND) and electrically active (NAD) acceptor-type structural defects in samples grown both under complete remelting of the starting ingot and under directed seed recrystallization of an ingot was studied. The concentrations NAD and ND and their distribution over the sample length were derived from the electrical characteristics (conductivity and the Hall effect) measured along the ingots in the temperature range 1.6–300 K. The contributions of various mechanisms to hole scattering were found from an analysis of the temperature behavior of the mobility. The results obtained were compared with the characteristics of samples grown following a similar program under normal conditions. The presence of NAD defects is characteristic of the initial crystallization stage of all samples. NAD is substantially lower (NAD ∼ 1015 cm‑3) than ND ∼ 1018 cm‑3 and decreases exponentially in the course of sample crystallization. Complete remelting under microgravity revealed indications of strong supercooling and spontaneous crystallization, as well as spatial oscillations of the electrical resistivity over the sample length caused by ND modulation. These observations are related to the specific features of the melting and crystallization in zero gravity, namely, the melt breaking away from the wall of the ampoule and the increasing role of Marangoni convection.
- Publication:
-
Physics of the Solid State
- Pub Date:
- July 2002
- DOI:
- 10.1134/1.1494616
- Bibcode:
- 2002PhSS...44.1241P
- Keywords:
-
- Crystallization;
- Electrical Resistivity;
- Tellurium;
- Hall Effect;
- Defect Formation