Ion beam synthesis and characterization of crystalline Si3N4 surface layers

A thin Si3N4 surface layer is formed by implantation of 60 keV 15N nitrogen ions into single-crystalline silicon left angle 100 right angle with a fluence of 5.6 x 1017 ions/cm2 and subsequent annealing (1295 C, 15 min) under high vacuum conditions. The 15N depth distribution is measured with the resonant nuclear reaction 15N(p,αγ)12C. The formation of Si-N bonds is proven by Fourier transform infrared spectroscopy using samples implanted with 14N ions and 15N ions, respectively. The crystallinity of the Si3N4 surface layer is studied by X-ray diffraction and transmission electron microscopy. The annealing process leads to the formation of a polycrystalline α-Si3N4 surface layer with a thickness of 90 nm. The analysis of high resolution TEM micrographs shows that the layer is split into two sublayers both consisting of single α-Si3N4 crystals with lateral extension up to 500 nm. (Abstract Copyright [2002], Wiley Periodicals, Inc.)