DIAMOND DEPOSITION ON POROUS SILICON BY PLASMA-ASSISTED CVD

For the first time, porous silicon has been used as a substrate for diamond deposition. The microwave-plasma-assisted chemical vapour deposition (CVD) method has been utilized to deposit the diamond films. Micro-Raman spectroscopy, scanning electron microscopy, profilometry and secondary-ion mass spectroscopy (SIMS) were carried out to characterize the films. Polycrystalline diamond films were grown simultaneously on polished and porous silicon to keep the deposition conditions identical for the two types of silicon. Different pre-treatment methods have been used for substrate seeding. It is found that the diamond films on porous silicon exhibit a smaller Raman peak shift than their counterparts on silicon. In addition the Raman peak of the diamond films on porous silicon possesses a higher intensity and a smaller linewidth. The results demonstrate that porous silicon substrates allow one to reduce the stress in diamond films and to enhance the quality of the diamond crystal structure. SIMS analysis indicated that carbon penetrated into the bulk of porous material during plasma-assisted CVD diamond deposition. The carbon concentration profile decreased from 1.8 x 10(5) to 10(3) counts s-1 monotonically with increasing thickness of porous silicon.