Enhancement of the ultraviolet absorption and Raman efficiencies of a few nanometer thick Si-on-insulator

We show that a 3–7 nm thick Si-on-insulator (SOI) film displays UV absorption and Raman enhancement compared to bulk Si at a proper thickness of the buried oxide layer between the film and Si substrate. Experiment shows ∼fivefold SOI Raman enhancement for 3–4 nm thick films while theory predicts enhancement up to a factor of ∼20 for 2 nm thick SOI. This discrepancy is attributed to non-uniformity of SOI thickness.