Optical and structural studies of nanocrystalline silicon thin film grown by rapid thermal annealing

Optical and structural properties of nanocrystalline silicon (nc-Si) thin film exhibiting blue-band photoluminescence (PL) at room temperature have been investigated. The nc-Si was grown by rapid thermal annealing at 800–1200°C for 1–5 min in vacuum from amorphous Si. PL intensity is increased with the annealing time and temperatures, while PL peak energy of 2.5-2.7 eV is less sensitive. The nc-Si exhibits distinguished properties such as little infrared absorption of SiO mode or the average grain size of on the order of 10 nm from blue-band light emitting nc-Si in literature. Thermoabsorption spectroscopy (TAS) signal, which monitors derivative of the optical absorption coefficient, sharply rises at 2.8 eV with small structures on 1200°C annealed nc-Si. The analysis of the TAS results implies that direct optical transitions between quasi-three-dimensional bands are likely to be responsible for the blue-band emission.