THERMAL NITRIDATION OF THE SI(110) BY NH3 - LEED AND AES STUDY

The Si(110) surface was thermally nitrided by NH3 gas. The investigati on was performed in the temperature range of 560-1050 degrees C by exp osure to a low pressure of ammonia (10(-5)-10(-6) Torr). Auger electro n spectroscopy (AES) and low energy electron diffraction were used to study the nitridation process. It was found that nitridation occurs by two different stages, namely, the initial fast step arbitrary limited at 500 L and the much slower and saturating step at higher exposures. AES data indicated that the growth mode is controlled by the growth t emperature. At high substrate temperature, the Si-nitride layer grows in the initial stage as a set of epitaxial islands. When the entire su rface is covered by islands, the growth mode converts to a layer-by-la yer one. At lower temperature the nitridation process is essentially l ayer-by-layer in the whole exposure range. During thermal nitridation the original Si(110) surface structure gradually converts to the Si-ni tride structure with hexagonal symmetry and the surface-lattice unite cell vectors of 2.85 Angstrom.