Synthesis of diamond-like carbon thin film on alumina substrate by microwave plasma enhanced chemical vapor deposition technique

Abstract

We have studied the influence of the main process parameters on the formation of the diamond-like carbon films on alumina substrates deposited by microwave plasma enhanced chemical vapor deposition (MW-PECVD) technique. Process parameters include methane (CH4) concentration (0.5-5%), deposition pressure (10-50 torr), and deposition time (5-30 hr). Raman analysis showed peak at around 1332 cm-1 and 1500-1600 cm-1, corresponding to diamond and graphite or amorphous carbon phase. The FWHM of the diamond peak decreased significantly with increasing deposition pressure and time, resulting in an increase of hardness and surface roughness of the films as well as nucleation density and growth rate. In contrast, an increase in CH4 concentration could lead to more secondary nucleation effect, resulting in a decreasing of grain size and surface roughness. Surface analysis by scanning electron microscopy (SEM) revealed a dense continuous film on the alumina substrate. It could be concluded that the main process parameters has significantly affected the characteristics of DLC films. The hardness of alumina found to increase from 7.3±2.0 GPa in uncoated to the maximum film hardness of 52.2±2.1 GPa, after coated with DLC film with CH4 concentration of 1%, deposition pressure of 30 torr, and deposition time of 30 hr.