Abstract: A unique class of microcrystalline semiconductor materials which can be modulated, within a crystalline phase, to assume any one of a large dynamic range of different Fermi level positions while maintaining a substantially constant band gap over the entire range, even after a modulating field has been removed. A solid state, directly overwritable, electronic and optical, non-volatile, high density, low cost, low energy, high speed, readily manufacturable, multibit single cell memory based upon the novel switching characteristics provided by said unique class of semiconductor materials, which memory exhibits orders of magnitude higher switching speeds at remarkably reduced energy levels. The novel memory of the instant invention is in turn characterized, inter alia, by numerous stable and non-volatile detectable configurations of local atomic order, which configurations can be selectively and repeatably accessed by input signals of varying levels.