Determination of interface layer strain of Si/SiO2 interfaces by reflectance difference spectroscopy

Detailed studies of the often-observed resonance feature near 3.4 eV in the reflectance difference spectrum of Si/SiO2 interfaces and Si surfaces show that the resonance is due to the intrinsic local-field effect, and that its energy position coincides with the E1 energy of bulk Si. Using the energy position of the resonance of the pseudomorphically grown Si/CaF2 interfaces as a reference point, the strain-induced resonance energy shift of the Si interface layer at several Si/SiO2 interfaces are obtained and the strain in these layers is determined. The results show that the interface layers are highly strained with an equivalent hydrostatic pressure of 0.79 GPa, but still maintain a high degree of order.