X-RAY PHOTOELECTRON-SPECTROSCOPY AND X-RAY-ABSORPTION NEAR-EDGE STRUCTURE STUDY OF STRUCTURAL-CHANGE OF PERHYDROPOLYSILAZANE TO SILICON-NITRIDE BY HEAT-TREATMENT

We studied the structural change of perhydropolysilazane to silicon ni tride during the process of heat treatment by means of in situ X-ray a bsorption near-edge structure (XANES) and X-ray photoelectron spectros copy (XPS), together with Fourier transformed infra-red (FT-IR) and te mperature programmed desorption (TPD) spectroscopies. It was revealed that nucleophilic attack on silicon atoms in the polymer began to proc eed above 200 degrees C, by nitrogen atoms in the polymer itself and a lso in atmospheric ammonia. From 400 degrees C to 600 degrees C, dehyd rogenation also occurred and produced dangling bonds which were attack ed by ammonia molecules to form the network of Si N-4 tetrahedra. Alth ough oxidation by residual moisture was observed to some extent at 600 degrees C, further heat treatment in ammonia formed Si-N bonds via re placement of oxygen atoms by nitrogen atoms to complete the formation of Si3N4-like structure.