In situ formation of tin nanocrystals embedded in silicon nitride matrix

Tin (Sn) nanocrystals (NCs) embedded in a silicon nitride (Si3N4) matrix have been fabricated in a cosputtering process employing low temperature (100 deg. C) substrate heating. Transmission electron microscopy (TEM) showed the formation of uniformly sized Sn NCs of 5.2±0.9 nm evenly distributed in the Si3N4 matrix. Both TEM and x-ray diffraction measurements showed that the Sn NCs adopted the semimetallic tetragonal β-Sn structure rather than the cubic semiconducting alpha-Sn structure. X-ray photoelectron spectroscopy revealed that the semimetallic state (Sn0) is the major component of Sn in the sample films. Our investigation demonstrates a pronounced effect of the substrate temperature on the formation of Sn NCs. The mechanism of in situ formation of Sn NCs is discussed. We suggest that the formation of uniformly sized Sn NCs is correlated with lowering the surface mobility of the nuclei due to the presence of the cosputtered Si3N4.