Raman scattering investigation of the structure of amorphous silicon in a-Si/SiO2 superlattice films

To clarify the structure of amorphous silicon (a-Si), with the thickness le ss than 5nm, affected by the interface between a-Si and a-SiO2 as well as t he structural changes after an annealing of 900 degrees C in N-2 gas atmosp here, Raman scattering investigation is carried out in a-Si/SiO2 superlatti ce (SL) films prepared by the sputtering method. Vibrational motion of stra ined a-Si at and near a-Si/SiO2 interface is influenced by the vibration of pressed a-SiO2 at the other side of the interface that results a blue shif t of transverse optic (TO) -like modes in a-Si. The narrow space of thin (< 2.5 nm in this work) a-Si layer impedes the crystallization to a-Si and the relaxation of energy during the crystallization event.