Control of the Crystallite Size and Dielectric Tissue in nc-Si/SiO₂ Plasma CVD Films: Origin of the Green/Blue and the Efficiency of the Red Photoluminescence

Abstract

Plasma CVD allows one a good control of the crystallite size and dielectric tissue in the nc-Si/SiO2 compact films. It is shown that the green/blue PL originates from SiO2 (s) ≡Si-OH groups whereas the red PL is associated with states at the nc-Si/SiO2 interface. With ≥ 1 nm thick SiO2 tissue the efficiency of the red PL increases by more than three orders of magnitude when the crystallite size decreases from about 8 to 2 nm in agreement with the theoretical predictions. If, at a constant crystallite size, the thickness of the SiO2 tissue is decreased to 0.2-0.3 nm, the PL intensity decreases by two orders of magnitude. Possible reasons of this effect are discussed together with the question of optimizing the electroluminescence. Microwave absorption is used to distinguish between free and localized (emitting PL) photogenerated carriers.

Origin of photoluminescence in nanocrystalline Si:H films

“…Veprek et al [24] prepared nc-Si:H films by hydrogendiluted-silane plasma or by chemical transport of silicon in hydrogen plasma. However, similarly to PS [4,25], these films exhibit a PL improvement only after a post processing treatment, like oxidation and annealing in forming gas (H 2 -N 2 ).…”

Possible Mechanism of the 30–100 Picoseconds Fast and Efficient Photoluminescence From nc-Si/a-SiO2Doped with Transition Metals

“…One notices that the PL spectra from the undoped sample which was stored in air for a long time is very similar to that reported by Lin et al and quite different from the PL of the W-doped samples. The dependence of the degree of polarization of the PL on the angle of the polarization vector with respect to z-axis (see [33,35]) is shown in Fig. 3.…”