Interaction of Hydrogen and Oxygen with Nanocrystalline Diamond Surfaces
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1203-J17-44
Interaction of hydrogen and oxygen with nanocrystalline diamond surfaces Thomas Haensel1, Syed Imad-Uddin Ahmed1, Jens Uhlig1, Roland J. Koch1, José A. Garrido2, Martin Stutzmann2, and Juergen A. Schaefer1,3 1 Institut für Physik and Institut für Mikro- und Nanotechnologien, Technische Universität Ilmenau, 98693 Ilmenau, Germany 2 Walter Schottky Institute, Technical University Munich, 85748 Garching, Germany 3 Department of Physics, Montana State University, Bozeman, Montana 59717, USA
ABSTRACT Nanocrystalline diamond films (NCD) are strong candidates for applications in a wide variety of fields. An important concern in all these applications is to understand the properties of variously prepared NCD surfaces. This contribution is focussed on the surface science study of hydrogen and oxygen containing NCD films using X-ray photoelectron spectroscopy (XPS) as well as high resolution electron energy loss spectroscopy (HREELS). Previous studies have demonstrated that hydrogen, oxygen, and gases from the ambient environment as well as water can result in drastic surface changes affecting conductivity, wettability, tribological properties, etc. In this contribution we analyzed differently prepared NCD surfaces as a function of parameters such as the annealing temperature under ultrahigh vacuum conditions (UHV). We are able to identify the thermal stability of a number of species at the interface, which are related to different characteristics of C-H, C-OH, C=O, and C=C bonds. Furthermore, a formation of graphitic-like species appears at higher annealing temperatures. An atomic hydrogen treatment was also applied to the NCD surface to obtain further information about the surface composition.
INTRODUCTION Diamond and related materials like diamond-like carbon are of great interest as transparent protective coatings, wear-resistant coatings, electronic devices, sensor systems, and bioelectronic systems. It was found that the graphitic-like species in amorphous carbon are responsible for the electrical behavior [1,2] while the diamond phase is important for the hardness. Furthermore, hydrogen bonded on the diamond surface can cause negative electron affinity (NEA), which might be of interest for electron emitting materials. In contrast, additional oxygen bonded to the surface can cause a positive electron affinity (PEA) [3]. Therefore, drastic changes of the electronic behavior can occur depending on the functional groups present on the surface. However, due to their electrical properties, nanocrystalline diamond is also used as a biosensor material [4]. Single crystalline diamond films are hard to produce and still very expensive. In most cases nanocrystalline diamond (NCD) is the first choice as these films can be manufactured on various substrates with a low roughness and good electrical properties [1,2] that can be controlled with appropriate doping [5]. Since in most applications diamond films are used under ambient conditions, fundamental research on the reactivity with hydrogen and oxygen of NCD surface
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