1. Parts of this work were presented earlier: S. R. Ovshinsky, at the Fourth Symposium on Vitreous Chalcogenide Semiconductors, sponsored by the Academy of Sciences of the USSR, Leningrad, 23–27 May 1967 (unpublished), and at the International Colloquium on Amorphous and Liquid Semiconductors, sponsored by the Rumanian Academy of Science, Bucharest, 28 September-3 October 1967 (unpublished), and in Proceedings of the Electronic Components Conference, Washington, D. C., May 1968 (McGregor and Werner, Inc., Washington, D. C., 1968), p. 313 ff.
2. S. R. Ovshinsky, U. S. Patent No. 3 271 591.
3. A discussion of the field of amorphous semiconductors and earlier references can be found in the review article by N. F. Mott, Advan. Phys. 16, 49 (1967).
4. The intrinsic behavior of amorphous semiconductors was first reported by A. F. Ioffé and B. T. Kolomiets; cf. Ref. 3.
5. The conductivity is expressed as σ = σ
0exp(-ΔE/kT).