Nucleation control and selective growth of diamond particles formed with plasma CVD

To obtain polycrystals with large and uniform grain size, diamond particles have been selectively formed on a SiO2 dot-patterned Si substrate using plasma-assisted CVD. After pretreatment by abrasive powders to increase diamond nucleation densities on both Si and SiO2, an Ar beam is used to irradiate obliquely the pretreated surface. As a result, diamond can no longer nucleate on Si; it nucleates only on one edge of the SiO2 dots and grows over the Si substrate to about 10 microns. Well defined polycrystals having equal grain sizes have been obtained. The role of the Ar beam irradiation on Si and on SiO2 is also discussed.