Investigation of the UV/O3 treatment of ultrananocrystalline diamond films

Surface analytical techniques such as XPS, time-of-flight secondary ion mass spectrometry (ToF-SIMS) and contact angle measurements have been applied to investigate the effects of UV/O-3 treatments used to render the original hydrogen termination of ultrananocrystalline diamond/amorphous carbon composite films to an OH-termination. The main parameter varied was the treatment time. For comparison purposes, a sample treated by amicrowave O-2 plasma for 10min, and a sample treated with UV light without the ozone-forming 185 nm emission have also been investigated. The standard UV/O-3 treatment leads to the following effects: i) the surface becomes oxidized with a final oxygen surface concentration of about 10%; ii) this oxygen is present at the surfacemainly in the form of OH groups; iii) the contact angle against purifiedwater drops from 85. for as-grown samples to 5 degrees +/- 2 degrees for UV/O-3-treated surfaces; iv) the surface energy increases by a factor of two, reaching 78 mN/m; in addition, this surface energy is almost exclusively of polar nature. These developments are almost completed after 20min of UV/O-3 treatment. Similar results can be achieved by O-2 plasma treatment, while blocking the ozone-forming 185 nm line of the UV lamp leads to only marginal changes of the as-grown surface, thus proving that O-3 plays a crucial role in the oxidation process. Copyright (C) 2010 John Wiley & Sons, Ltd.