Visible photoluminescence from plasma-synthesized SiO{sub 2}-buffered SiN{sub x} films: Effect of film thickness and annealing temperature

The effect of the film thickness and postannealing temperature on visible photoluminescence (PL) from SiN{sub x} films synthesized by plasma-assisted radio frequency magnetron sputtering on SiO{sub 2} buffer layers is investigated. It is shown that strong visible PL is achieved at annealing temperatures above 650 deg. C. The optimum annealing temperature for the maximum PL yield strongly depends on the film thickness and varies from 800 to 1200 deg. C. A comparative composition-structure-property analysis reveals that the PL intensity is directly related to the content of the Si-O and Si-N bonds in the SiN{sub x} films. Therefore, sufficient oxidation and moderate nitridation of SiN{sub x}/SiO{sub 2} films during the plasma-based growth process are crucial for a strong PL yield. Excessively high annealing temperatures lead to weakened Si-N bonds in thinner SiN{sub x} films, which eventually results in a lower PL intensity.