EFFECT OF ARGON ADDITION DURING ECR MODE NUCLEATION OF DIAMOND FILMS GROWN BY MPCVD

摘要

Diamond films were deposited on (100) silicon wafers in a two step process of low pressure Electron Cyclotron Resonance (ECR) mode nucleation followed by high pressure microwave plasma enhanced Chemical vapor deposition (MPCVD). The ECR nucleation process at 4.67 Pa in a hydrogen-argon-methane plasma led to the formation of nuclei of carbon based material of 20-50 nm size with high number density in addition to large transparent grains of about 5-50 μm size. Optical emission spectroscopy indicated higher degree of ionization with increasing argon during the nucleation stage. Raman spectra of the large grains did not show the characteristic diamond peak. Further deposition at 4000 Pa on the nucleated substrates led to the formation of discontinuous diamond films with well pronounced (100) facets. Raman spectra of these films showed the first order phonon peak of diamond at 1332 cm{sup}(-1) as well as a broad peak around 1555 cm{sup}(-1) indicating presence of some sp{sup}2 carbon content. There was no orientation relationship between the cubic axes of the silicon substrate and those of the (100) facets on the films ruling out diamond epitaxy. Increasing the argon concentration in the hydrogen-methane plasma during the nucleation step had the effect of decreasing the nucleation density of diamond. Addition of argon during the ECR stage did not generate any specific advantage to the diamond films grown by the MPCVD process although the stability of the plasma and the degree of ionization were higher.