Effect of Molten Temperature on the Formation of Lotus-type Porous Silicon during Unidirectional Solidification

Porous silicon with cylindrical pores was fabricated by mold casting method in hydrogen atmosphere. The pores were evolved by insoluble hydrogen when the molten silicon was solidified. The effect of liquid temperature on the formation of porous silicon was examined in the melting temperature range of the liquid from 1773 to 1973 K. The porosity increases with increasing liquid temperature. The average pore diameter decreases with increasing liquid temperature. Fine dendrite structure can be found in 1773 K sample, while the dendrite structure cannot be observed in 1873 and 1973K samples alter the etching. The X-ray diffraction pattern from transversal cross section of the samples shows polycrystalline phase for 1773 K, 100 orientation for 1873 K and 110 orientation for 1973 K sample.