The surface properties on both sides of the isolated diamond film

The polycrystalline diamond films in this research were deposited on silicon substrates using a methane–hydrogen gas mixture by the microwave plasma chemical vapor deposition (MPCVD) system. Prior to deposition, the silicon wafers were pretreated by a photoresist in which 0.1 μm diamond powder is suspended. The isolated diamond film was then obtained by etching the backside of the silicon wafer with KOH solution. The bottom surface of the isolated diamond film exhibited a much smoother surface profile than the top surface of the isolated diamond film. From XPS analysis, the oxygenated phenomenon was detected for the as-deposited diamond film and increased for both surfaces of the isolated diamond film after the back-etching process. It was noted that the oxygenated phenomenon did not degrade the film quality since the quality of the isolated diamond film improved after the back-etching process. An estimated 600 Å thick SiC layer and an amorphous carbon interlayer was found on the bottom surface, which is in the diamond–Si interfacial region of the isolated diamond film. Experimental results showed that the film quality was not dependent on the grain size and roughness of the diamond film. The shift of the characteristic diamond peak was due to the strain force that was formed in the interface of diamond–Si during the cooling-down period of the deposition process. The thick layer of SiC and the amorphous carbon interlayer also affected the film quality in the interfacial region during diamond deposition and the noise of the Raman spectrum increased for the bottom surface of the isolated diamond film.