Surface potential of functionalised nanodiamond layers
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1203-J17-01
Surface potential of functionalised nanodiamond layers I. Kratochvílová1, A. Taylor1, F. Fendrych1, A. Kovalenko1 and M. Nesládek2 1
Institute of Physics, Academy of Sciences Czech Republic v.v.i, Na Slovance 2, CZ-182 21,
Prague 8, Czech Republic 2
Hasselt University, Institute for Materials Research (IMO), Wetenschapspark 1, B-3590
Diepenbeek, Belgium
ABSTRACT Carbon nanomaterials especially ultrananocrystalline diamond and nanocrystalline diamond films have attracted more and more interest due to their unique electrical, optical and mechanical properties, which make them widely used for different applications (e.g. MEMS devices, lateral field emission diodes, biosensors and thermoelectrics). Nanocrystalline diamond can also offer novel advantages for drug delivery development. Recent studies have begun to use nanocrystalline diamond for in-vivo molecular imaging and bio-labeling. To enable grafting of complex bio-molecules (e.g. DNA) the surface of ND requires specific fictionalization (e.g. H, OH, COOH & NH2). Due to the surface dipoles of functionalised nanodiamond band bending at the surface can be easily induced and from the measured band bending we can deduce the type of the fictionalization on the surface. The surface potential of H-terminated and OH terminated nanodiamond layers was investigated by Kelvin probe microscope. From the change of the surface potential value (as the departure of the material surface from the state of electrical neutrality is reflected in the energy band bending) the work function of the H-terminated nanodiamond layer was established to be lower than OH-terminated nanodiamond layer. The surface potential difference can be explained by the surface dipole induced by the electronegativity difference between the termination atoms.
INTRODUCTION From carbon nanomaterials specially ultrananocrystalline diamond (UNCD) and nanocrystalline (NCD) diamond films have attracted more and more interest due to their unique electrical, optical, and mechanical properties, which make them widely used for different applications: MEMS devices, lateral field emission diodes, biosensors, thermoelectrics, etc [1-2]. The physico-chemical properties of diamond surfaces are key to achieve the desired properties of these devices. In order to produce high performance devices, therefore, it will be essential to control the surface physico-chemical properties of the diamond. It has been reported [3] that physico-chemical properties of diamond surfaces are closely related to the surface chemisorbed species on the surface. Hydrogen chemisorption on a chemical vapor deposition -grown diamond surface is well-known to be important for stabilizing diamond surface structures with sp3 hybridization. Many reports have suggested that an H-chemisorbed
structure is necessary to provide a negative electron affinity condition on the diamond surfaces. Oxidized diamond surfaces [4] usually show characteristics completely different from those of the H-chemisorbed diamond surfaces. The unique electron affini
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