Crystal direction dependence of quantum confinement effects of two-dimensional Si layers fabricated on silicon-on-quartz substrates: modulation of phonon spectra and energy band structures

Abstract

We experimentally studied the crystal direction dependence of phonon confinement effects (PCEs) and bandgap (EG) modulation of a two-dimensional (2D) Si layer fabricated on (100) silicon-on-quartz (SOQ) wafers without a handle Si substrate. For the first time, by polarization Raman spectroscopy, in the case of Raman intensity spectra in the asymmetrical broadening region owing to the PCEs in the 2D Si layer, we demonstrated that the incident laser polarization direction dependence of the Raman intensity deviates from the Raman selection rule. However, a photoluminescence (PL) method shows that the EG expansion is isotropic in the 2D Si layer. On the other hand, the reflectivity of the 2D Si layer in UV region is also modulated. The reflectivity property modulation is possibly attributable to the energy band modulation in the 2D Si layer.