Effects of annealing on the chemical states and the luminescence properties of nitrogen-controlled silicon-nitride films

We investigate silicon-rich silicon-nitride (SRSN) films grown by using plasma-enhanced chemicalvapor deposition (PECVD). We fixed the flow rate of silane and varied that of the nitrogen gas. We measured the photoluminescence (PL) spectrum and the chemical states of the samples by using X-ray photoelectron spectroscopy (XPS). Observing the Si 2p core-level spectra, we note that the less the silicon amount is in the matrix, the shorter the wavelength of the PL peak position has due to the reduced size of nc-Si clusters. Investigating the effect of annealing on the chemical states and the luminescence properties of the sample, we report that the PL intensity is strongly enhanced and reaches a maximum value after the first 5 minutes of annealing and is 12 times stronger than that of the as-deposited sample while the PL intensity decreases gradually for longer annealing times. We note also that the PL peak position shifts accordingly toward the red. Analyzing the chemical state components of the Si 2p core-level spectra, we extract several components of different chemical states. Using the chemical state analysis, we discuss the relation between the intensity enhancement of the samples and the chemical state changes of silicon-nitrogen bonding.