Preparation, Structure, Photoluminescence And Electrical Resistivity Of Solid Sintered Porous SiC

Investigations are made of porous SiC (PSC), both as a potentially attractive material for fabricating UV light emitting diodes (LEDs), efficient photodetectors and hydrocarbon gas sensors, and as a novel substrate for epitaxy, chiefly because of its much higher photoluminescence (PL) emission efficiency than that from bulk SiC. In this paper, presentation is given of PSC being prepared by solid sintering process as employed in powder metallurgy and ceramics industry and measurements are made of its PL and electrical resistivity.The preparation process of sintered PSC involves powder purifying, pressed powder compact preparation, sintering process and final treatment. Pressed compacts are made under various pressures ranging from SOOMPa to lOOOMPa. Sintering time ranges from 3 to 10 hours, and sintering temperature ranges from 160CTC to 1900癈, under an Ar. protection of 1.0 atm. After sintering, the samples are dry-oxidized in an oxidization furnace and then have their excessive carbon removed by diamond-cream grinding or direct grinding.Its structure and composition are SEM, XPS and XRD analyzed. The results show that the sintered PSC is composed of a network of micrometer-sized cavities and its main compositions are 6H-S1C, 3C-SiC and a small quantity of CSi.Its PL spectrum is measured under the excitation of an ultraviolet (UV) light beam from a He-Cd laser (325 nm, lOmW). Samples without oxidization and grinding exhibit a major luminescence peak at 2.05eV and a minor one at 2.26eV at the room temperature. Those samples treated show a major peak at 2.02eV and a minor one at 2.13eV at a given low temperature and experiences a blue-peak-shift at room temperature. A defect model isAbstractsuggested to account for the PL of sintered PSC.As shown by the measurements, the electrical resistivity of sintered PSC has a tendency of first decreasing and then increasing as the sintering temperature and/or sintering time increase. Also it decreases with the increased pressure on the pressed powder compact.