Optical and electronic properties of periodic Si nanostructures

Nanogratings (NGs) on the surface of the top Si layer of a Si/SiO2/ substrate device structure were prepared using laser interference lithography. Electron transport, photoluminescence, and Raman scattering were then studied on the plain Si and NG Si structures to see the effect of NG introduction. As a result of NG-introduction and very likely G-doping maintenance, all samples studied in this work displayed a 2 to 3 order of magnitude reduction in resistivity for NG Si. The Hall coefficient indicated that electrons are main charge carriers that is also expected for exactly G-doping. Plain Si layer did not show any photoluminescence either for 532 nm (2.38 eV) or 325 nm (3.81 eV) laser excitation. A broad photoluminescence band, composed of a number of almost equidistant peaks was observed on NG Si layer between the photon energies 1.5 and 3.5 eV. Both Stocks and anti-Stocks components for 522.65 cm−1 phonons at room temperature were observed in the Raman spectra of NG Si layer. Estimated from the ratio between the intensities of Stocks and anti-Stocks components, the drop (if any) in phonon gas temperature below ambient (295 K) does not exceed 3 K.