Prior to deposition, the titanium/silicon substrates were pre-treated by two techniques, first technique is diamond powder polished and the second technique is diamond powder polished with hydrogen (H2) plasma etching, respectively. The nanodiamond films were deposited on the titanium/silicon substrate utilizing microwave plasma chemical vapor deposition system with a gas source mixed by Ar, H2 and CH4. Rapid thermal annealing (RTA) technique was then adapted as the post-treatment process.
It was observed from the Raman spectra that the ratio of D band/G band of the nanodiamond film for the first and second pre-treatment techniques are about 4.9 and 3.3, respectively. After rapid thermal annealing (RTA) post-treatment, the ratio of D band/G band is decreased to approximately 1.26 and 1.03, respectively. It was suggested that the defects and the disordered bonding structures in the nanodiamond films are clearly decreased by the RTA post-treatment.
Furthermore, the turn-on electric field of the nanodiamond film for the first and second pre-treatment techniques is about 9.8 V/µm and 5.9 V/µm, respectively. After the RTA post-treatment, the turn-on electric field is decreased to approximately 6.2 V/µm and 5 V/µm, respectively. Therefore, it was indicated that the film quality and the field emission properties of the nanodiamond films are strongly improved by the RTA post-treatment.
Keywords: nanodiamond, titanium/silicon substrate, H2 plasma pre-treatment, RTA post-treatment, field emission
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