Luminescence properties of nanocrystalline silicon films

Nanocrystalline silicon (nc-Si) films deposited by plasma-enhanced chemical vapor deposition exhibited room-temperature photoluminescence (PL) with two peaks at around 1.8 eV (700 nm) and 2.2–2.3 eV (540–560 nm). The first 1.8-eV peak is related to a quantum size effect and another peak to the SiH-related bonds. The average grain size, 〈δ〉, and crystalline volume fraction, ρ, decrease with decreasing gas pressure. By contrast, all of the PL peak energy, PL intensity and optical band gap increase. In addition, by increasing the H2 flow rate, rf power and deposition temperature, it is found that the values of 〈δ〉, ρ and PL intensity increase and PL peak energy decreases.