Electron spin resonance in amorphous germanium and silicon

Abstract

Abstract The contributions to the spin resonance absorption lines observed in amorphous silicon and germanium are discussed in terms of the different relaxation processes. It is shown that besides a g-value distribution, hyperfine interaction contributes significantly. Dipolar and anisotropic exchange interactions are shown to be of minor importance except at the highest spin densities. The temperature-dependent increase in linewidth is explained by a modulation of the spin-orbit interaction owing to the motion of the carriers. A semiclassical model is used to show that the distribution of spin-flip times given by a sequence of consecutive hops in the framework of variable-range hopping can lead to the observed changes in linewidth and lineshape. Some exchange interaction is required to narrow the lines and to transfer the hopping-induced spin-flip rate to the spins far below the Fermi level. An anti-ferromagnetic exchange of the order of 1 K as reported recently, however does not seem likely in the light of the observed spin-resonance lineshapes.