Stress‐enhanced crystallization in amorphous selenium films
1.There are also two metastable phases in which the molecules form stacks of eight‐member rings; see Mellor, Comprehensive Treatise on Inorganic and Theoretical Chemistry (Longmans, Green, New York, 1930) Vol. 10, p. 701;
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4.A much different charged‐defect model has been proposed by M. Kastner, D. Adler, and H. Fritzsche [Phys. Rev. Lett. 37, 1504 (1976)]; their model does not a priori preclude the mechanism proposed by this letter.
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15.The exponent of P in Eq. (5) was measured to be 1.45 by Keezer and Bailey (Ref. 16), but that value only applies to the shorter chain lengths prevalent at the higher temperatures for which they did their measurements. As the chains get longer, the exponent increases to the 3.4 used here; see G. C. Berry and T. G. Fox, Adv. Polym. Sci. 5, 261 (1968).
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18.A model which did not include rings would yield the same result. The critical feature is the creation (destruction) of chain ends.
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21.If this effect is sufficiently strong, one would more correctly describe a‐Se with the valence alternation model of Kastner et al. (Ref. 4). Given an increased volume for the chain branch points, however, this analysis should still be applicable. Unlike a branch point in an organic polymer which is immobile, in a‐Se the branch point could readily slide along the chain under stress, and so should not affect the viscosity.
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23.The crystallization rate of the surface cylindrites was not very accurately established since is sensitive to such external conditions as humidity and chemical vapors; see Ref. 11 and Y. S. Chiang and J. K. Johnson, J. Appl. Phys. 38, 1647 (1967).
24.η cannot be measured directly in this temperature range owing to interference from crystallization. However, M. Cukierman and D. R. Uhlmann [J. Non‐Cryst. Solids 12, 199–266 (1973)] have bounded the region with viscosity measurements at both higher and lower temperatures. I have linearly interpolated
25.Young’s modulus was determined from ultrasonics measurements [L. J. Graham and R. Chang, J. Appl. Phys. 36, 2983–6 (1965)].
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28.This effect is seen in the increased solubility of a‐Se in when exposed to light, which presumably tends to cleave the long chain molecules. It was apparently first seen at Energy Conversion Devices Co. in 1972 [J. P. de Neufville (private communication)].
29.It was pointed out by G. Lucovsky that the dissolution of a‐Se in is activated by absorbed photons [G. Lucovsky, in The Physics of Selenium and Tellurium, edited by E. Gerlach and P. Grosse (Springer, Berlin, 1979), pp. 178–92],
29.and that the observed increase in solubility near the crystallite growth edge might be explained alternatively by a stress induced lowering of the band gap Normally and an a‐Se film appears dark red. Stress σ reduces and increases the absorption of red light. Although the coefficient is quite large [ see G. Lucovsky, in Proceedings of the Seventh International Conference on Amorphous and Liquid Semiconductors, edited by W. E. Spear (G. G. Stevenson, Dundee, 1977), p. 48], the stress present at the growth face causes only a 0.3% reduction in it is unlikely that mechanism plays a significant role in the observed solubility enhancement.
30.Handbook of Physics, edited by E. U. Condon and H. Odishaw (McGraw‐Hill, New York, 1958), pp. 6–121.
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