Annealing studies of PbTe and Pb1−xSnxTe

Abstract

The results of single-zone annealing of 76 samples of Pb1−xSnxTe are reported, covering the entire composition range from pure PbTe to pure SnTe. Some of the sample preparation work overlapped and improved on the work of others, while some of the results, particularly in the alloy samples, are new. Annealing times, temperatures, source ingot preparation, resulting carrier concentrations, and 77 °K Hall mobilities are reported. The Knight shift of the Pb207 nuclear magnetic resonance and the NMR line shape were used for additional sample characterization. This interesting technique was applied most successfully in the pure PbTe samples with carrier concentrations below 1018 cm−3. It was discovered from NMR studies on powders that strain damage introduced by powdering could completely compensate p-type PbTe. No corresponding effect was noted in n-type PbTe, suggesting the presence of damage-induced levels in the gap.

First-principles calculation of intrinsic defect chemistry and self-doping in PbTe

“…The computed free carrier concentrations are within half to an order magnitude of the experimental values 34,36,37 depending on the temperature, as shown in Fig. 6c and d. HSE + SOC calculations without the G 0 W 0 band edge shifts, predict the correct n-type conductivity under Te-poor conditions, but fail to predict the p-type conductivity under Te-rich conditions at low temperatures.…”

“…35,60 The experimental data in Fig. 6c and d is from Hall measurements [34][35][36][37] done between 77-100 K on quenched samples that are annealed at a much higher temperature range, between 400 and 1100 K. Therefore carrier concentrations from the charge neutrality condition (Eq. 3) are computed at 100 K, using defect concentrations corresponding to the annealing temperature of the experiment.…”

“…Eg(T) correspond to concentrations computed using band gap and band edge energies as function of temperature in defect formation energy (DFE), and Eg(T = 0 K) correspond to concentrations computed using DFE with band gap of 0.2 eV and band edges at T = 0 K. Experimental data for free carrier concentrations is adopted from Refs. 34,35,36,37 First-principles calculation of intrinsic defect A Goyal et al…”

“…This is in contrast to experimentally-observed p-type conductivity under Te-rich conditions and n-type under Te-poor conditions. [34][35][36][37] Given the contested accuracy of defect calculations in compounds with strong spin-orbit coupling, this work focuses on PbTe to establish best practices in defect and dopability calculations. By using hybrid functionals (HSE stands for HSE06 38,39 ) along with spin-orbit coupling to perform defect calculations and quasi-particle GW approach (at G 0 W 0 level) to describe the valence and conduction band edges, we obtain (1) a quantitatively accurate description of the defect chemistry and associated free carrier concentrations in PbTe, and (2) bipolar doping behavior, in agreement with experiments.…”

Graded Design of Carrier Concentration in Thermoelectric PbTe System by Heat-treatment

“…PbTe has been reported to change n by heat-treatment. 6,7) If n changes continuously by heat-treatment using a temperature gradient, then heat treatment using a temperature gradient may form a continuous gradient of n.…”