Mixed-phase micro-crystalline material, prepared by plasma-enhanced chemical vapor deposition, was investigated by using continuous wave and time-resolved electron spin resonance techniques under conditions of thermal equilibrium or illumination. Variations in plasma excitation frequency and gas mixture led to differences in the crystal volume fractions and grain size. Three main electron spin resonance contributions were found and were attributed to dangling bonds in differing structural environments, and to conduction electrons. The g-values of the dangling bonds were shifted with respect to the g-value of a dangling bond in amorphous material. The dangling-bond spin-density remained largely unchanged over a wide range of plasma excitation frequencies, but increased at the highest plasma excitation frequency and also increased at high silane concentrations when amorphous growth conditions were attained. Doping changes, which varied the dark conductivity over 5 orders of magnitude, caused the dangling-bond spin-density to alter by a factor of only 4; and it decreased significantly only for the highest p-doping levels. Pulsed electron spin resonance measurements revealed 2 distinct spin-lattice relaxation times in the material. The relaxation time of dangling bonds was very similar to the corresponding relaxation time in amorphous Si, and the relaxation time of the conduction electrons was several orders of magnitude less than the relaxation time of the dangling bonds.

F.Finger, J.Müller, C.Malten, H.Wagner: Philosophical Magazine B, 1998, 77[3], 805-30