Abstract

The amounts and compositions of residual gases formed in sealed ampoules loaded with different sources (elements and II–VI and IV–VI compounds) were investigated. A given source was subjected to a series of heat treatments, with intermediate measurements and removal of the gas accumulated in the system. The results of these experiments are discussed in terms of the underlying thermochemical and kinetic phenomena and practical limitations to reducing the amount of residual gases in sealed ampoules.

Author Keywords: A1. Impurities; A1. Purification; A1. Residual gas

66.30.Jt; 81.05.Dz; 81.05.Hd; 81.20.Ym

Article Outline

1. Introduction

2. Experimental procedures

3. Results and discussion

3.1. Single annealing

3.1.1. Elements

3.1.2. PbTe

3.1.3. Tellurides of Sn, Cd, and Zn

3.1.4. Selenides

3.2. Subsequent heat treatments

3.2.1. Elements

3.2.2. Compounds

4. Discussion

5. Summary

Acknowledgements

Appendix

References

(7K)
Fig. 1. Dependence of the maximum amount (in terms of pressure) of gas that can be formed as a function of the concentration of oxide impurities in the source. n—the amount of source in moles, T—the temperature, V_f—free volume in the system.

(4K)
Fig. 2. Schematic representation of the experimental system.

(11K)
Fig. 3. Pressures of residual gas formed in ampoules with elemental source after consecutive thermal processings. (a) sources outgassed at RT; (b) sources thermally pretreated prior to ampoule seal-off.

(12K)
Fig. 4. Pressures of residual gas formed in ampoules with PbTe source after consecutive thermal processings. (a) pretreatment without hydrogen: 700°C/vacuum/0.15 h; (b) pretreatment with hydrogen: 700°C (0.5 atm H₂/0.15 h+vacuum/0.1 h).

(5K)
Fig. 5. Pressures of residual gas formed in ampoules with highly contaminated SnTe source after consecutive thermal processings. Source ground and sifted. Pretreatment: 700°C (0.5 atm H₂/0.15 h+vacuum/0.1 h).

(5K)
Fig. 6. Pressures of residual gas formed in ampoules with ZnSe source after consecutive thermal processings. Source ground and sifted. Pretreatment: 700°C (0.5 atm H₂/0.15 h+vacuum/0.15 h).

(6K)
Fig. 7. Degree of volatization of oxides by carbon as a function of the Gibbs energy of formation of carbon monoxide from carbon and MeO oxide.

(2K)
Fig. 8. Schematic representation of a collision of gas with a spherical particle.

References

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