Raman study of de-relaxation and defects in amorphous silicon induced by MeV ion beams

Raman spectroscopy is used as a probe of the state of amorphous Si (a-Si) and damaged crystalline Si. MeV ion beams have been used to irradiate structurally relaxed a-Si. When the density of Si atoms displaced by nuclear collisions exceeds 5%, the a-Si is ‘‘de-relaxed’’, and thus returns to its as-implanted state. This behavior is an indication that point defect complexes exist in a-Si and play an important role in the process of structural relaxation.