Raman microscopy investigations of structural phase transformations in crystalline and amorphous silicon due to indentation with a Vickers diamond at room temperature and at 77 K

Abstract

Raman microscopy has been used to investigate phase transitions within Vickers diamond residual indentations, made at room temperature and at 77 K, in single crystal Si(100) and 0.3 μm thick amorphous silicon film deposited on a sapphire single crystal. It has been found that for room temperature residual indentations in the single crystal silicon (Si-I) and amorphous silicon film phase transition to the Si-III phase occurs, as indicated by the existence of Raman peaks corresponding to this phase. On the other hand, in the case of the indentations made at 77 K, only the Si-I crystalline phase and amorphous silicon were found within the residual indentations. It has been suggested that when Vickers diamond indentations are made at 77 K, there is no phase transition to the Si-II (i.e. the β-Sn phase) during indenter loading, which would give rise to the Si-III phase on the removal of indenter load. Moreover, the existence of a very strong peak due to the Si-I phase gives further support to the suggestion that during Vickers indentations in single crystal silicon and in amorphous silicon at 77 K there is no structural phase transition. It has also been suggested that during room temperature indentations there is a substantial temperature rise, which may help to cause structural phase transitions.