GAS CONDENSATION OF ULTRAFINE SILICON PARTICLES USING DC MAGNETRON SPUTTERING

Ultrafine silicon particles with typical diameters of 6 nm to 30 nm we re prepared by dc magnetron sputtering at 175 watts in argon gas at pr essures om 100 mtorr to 700 mtorr. At 100 mtorr, both granular amorpho us film and amorphous particles were observed, indicating that the gro wth occurred under conditions near the threshold for supersaturation o f the silicon vapor. Depositions at higher pressures showed that the s izes of the particles did not monotonically increase with pressure. In addition, particles grown at 100 mtorr and 300 mtorr were mainly amor phous in structure, whereas those grown at 500 mtorr and 700 mtorr con tained a mixture of amorphous and diamond-cubic crystalline material. Futhermore, the sizes of the particles were found to depend upon wheth er they were collected from the top or the bottom of the cooled substr ate. The evolution of the crystalline phase may occur due to growth in a more thel malted silicon vapor which occurs at higher argon gas pre ssures.