Structural and Optical Properties of Nanocrystalline Silicon Films Deposited by Plasma-Enhanced Chemical Vapor Deposition

Nanocrystalline silicon (nc-Si) films were deposited by plasma-enhanced chemical vapor deposition using SiF4/SiH4/H2. The structural and optical properties of the nc-Si films were examined by varying the deposition temperature, Td, for two different series of films with different H2 and SiF4 flow rates: [H2]=30 sccm and [SiF4]=0.38 sccm for series A films, and [H2]=0.0 sccm and [SiF4]=0.5 sccm for series B films. We found two photoluminescence (PL) bands at around 1.7–1.8 eV and 2.2–2.3 eV. The decrease in the peak energies, EPL, of the 1.7–1.8 eV PL band for series A films was consistent with the increase in the average grain size, , while EPL for series B films was related to . The difference between the PL processes for series A and B films was interpreted in terms of the difference between the etching rates of F and H radicals, depending on Td. The changes in EPL and the optical band gap were analyzed based on a simple confinement theory.