Investigation of the UV/O 3 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 a microwave O 2 plasma for 10 min, 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 surface mainly in the form of OH groups; iii) the contact angle against purified water drops from 85° for as‐grown samples to 5° ± 2° 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 20 min 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 © 2010 John Wiley & Sons, Ltd.