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

The Si(110) surface was thermally nitrided by NH3 gas. The investigation was performed in the temperature range of 560-1050 degrees C by exposure to a low pressure of ammonia (10(-5)-10(-6) Torr). Auger electron 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 temperature. At high substrate temperature, the Si-nitride layer grows in the initial stage as a set of epitaxial islands. When the entire surface is covered by islands, the growth mode converts to a layer-by-layer one. At lower temperature the nitridation process is essentially layer-by-layer in the whole exposure range. During thermal nitridation the original Si(110) surface structure gradually converts to the Si-nitride structure with hexagonal symmetry and the surface-lattice unite cell vectors of 2.85 Angstrom.