Vibrational analysis of compositional disorder in amorphous silicon carbon alloys

Raman and Infrared spectroscopies have been used to characterise the compositional disorder in a-Si1-xCx alloys. Samples with different carbon concentration have been prepared by ion implantation of carbon into a silicon matrix and have been annealed at different temperatures in order to follow the evolution of disorder. The obtained results show an increase of the magnitude of compositional disorder with carbon concentration and a reduction of such a disorder upon thermal treatments up to 1000 degrees C where it vanish during the amorphous-to-crystalline phase transition. A quantitative interpretation of the compositional disorder has been given as a function of the carbon concentration and annealing temperature.