Structure and electrical properties of silicon thin films on zirconia-tungsten composites

The structure and electrical properties of E-beam evaporated silicon thin films were studied and the conduction mechanism of silica films deposited on ZrO2 - W composites was analyzed. Electron-beam evaporation deposition of 1-4 μm of silicon on ZrO2-W composites in the temperature range 465 to 5600C produced polycrystalline silicon films with a (110) epitaxial orientation in the initial stages of deposition. The polycrystalline structure was not maintained and the films transitioned to amorphous with increasing thickness. For the polycrystalline component of the silicon films, the average crystallite size of 500 A did not change nor did the quantity of crystalline material increase on heat treatment until above 10000C. From 10000C to 12500C, the crystallite size increased to 800 A and the increase in volume of crystalline material was compatible with growth of crystallites formed on deposition with no evidence of nucleation of new crystallites during heat treatment. The (110) preferred orientation of the crystalline component was maintained throughout heat treatment. The conduction process in the silicon films was analyzed by estimating the relative crystalline and amorphous contents together with the structural changes controlled by deposition parameters, i.e., film thickness, deposition rate, and substrate temperature. The I-V characteristics of the silicon films were thickness dependent and obeyed the field assisted thermal ionization relationship