Ultrathin silicon nitride multilayer films were prepared by varying silane/ammonia flow ratios 1/10 and 1/20 alternately in a silicon nitride hot-wire chemical vapor deposition chamber. Some films were annealed at 1000°C for 1 h in an argon environment. Cross-sectional transmission electron microscopy shows~6 nm silicon clusters formed in the annealed film. Strong visible red emission in the wavelength range 810-820 nm was detected from the films when excited with the 325 nm He-Cd laser excitation. A blueshift in the photoluminescence of the annealed film with respect to the as-deposited film is attributed to the silicon quantum confinement due to the presence of silicon clusters. Disappearance of the photoluminescence peak at 521 nm related to silicon dangling bonds in the annealed film in comparison with the as-deposited film was confirmed by the photoluminescence measurements.
The fabrication of ultra thin silicon nitride (SiNX) layer (< 2 nm) on amorphous silicon (a-Si) in-situ hot-wire CVD by decomposing ammonia (NH3) gas is reported. Approximately 1.5 nm thin SiNXis formed by nitridation of 40 nm thick a-Si for 10 min at substrate temperature of 250 °C. The amorphous phase of SiNXformed on a-Si and a-Si layer deposited on c-Si wafer is identified by Raman spectroscopy. The formation of ultra thin SiNXby nitridation of a-Si at 250 °C is confirmed by X-ray photoelectron spectroscopy (XPS) depth profile measurement of SiNX/a-Si structured film. The report indicates that the HWCVD method can be used for fabricating superlattice structures consisting of ultra thin SiNXlayers (< 2 nm).
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