Correlation of the electrical properties of metal contacts on diamond films with the chemical nature of the metal-diamond interface. I. Gold contacts: A non-carbide-forming metal

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Abstract
The gold–polycrystalline-diamond interface has been characterized by x-ray-photoelectron-spectroscopy (XPS), Auger-electron-spectroscopy (AES), and current-voltage (I-V) measurements. The I-V characteristics of gold contacts on polycrystalline diamond were correlated with interface observations by XPS and AES. Minimal interaction between the gold and diamond due to the inert nature of both materials led to the formation of rectifying contacts. Various predeposition treatments of the diamond including vacuum annealing, wet chemical cleaning, and argon sputtering were also examined. Predeposition vacuum annealing desorbed some of the physisorbed oxygen from the diamond surface. The wet chemical cleaning effectively removed nondiamond carbon. However, these treatments did not influence the interaction between the gold and polycrystalline diamond. Also, there was no difference in the I-V characteristics between the gold contacts on the treated diamond surface and those on the nontreated surface. Argon sputtering cleaned the diamond surface but created a damaged surface layer which appeared to be graphitic. As-deposited gold formed Ohmic contacts on the sputtered surface due to the presence of the damaged layer. Once annealed, however, these contacts became rectifying probably because the damaged layer was absorbed into the gold overlayer.