Amorphous semiconductors

There has been a recent surge of interest in the subject of amorphous semiconductors, a field which only a few years ago was generally considered to be about as scientific as witchcraft or alchemy. The major reason for the change in attitude is not difficult to pinpoint: the turning point was the publication by Ovshinsky¹ detailing the various types of switching phenomena that characterize a large class of amorphous solids, and the subsequent publicity describing many potential applications of these phenomena.^2,3 But, in addition, the field presents several surprising features that stimulate pure academic interest. Firstly, a serious investigation of the properties of amorphous semiconductors requires not only familiarity with one particular area of science or engineering, but rather a detailed knowledge of results from the combined fields of physics, chemistry, metallurgy, and electrical engineering. Secondly, although the study of amorphous semiconductors, especially when compared with that of crystalline materials, is certainly in its infancy, and much fundamental experimental and theoretical work remains to be done, still much sophisticated thought has been devoted to the subject over the past 10 years and great strides have been made in understanding the basic principles. Finally, even a superficial investigation of amorphous semiconductors brings home rather strikingly the fact that solid state physics, even up to the present time, is being taught incorrectly!