XPS and UPS investigation of the diamond surface oxidation by UV irradiation

Hydrogen terminated nanocrystalline Diamond (H-NCD) is a promising candidate for bio-electronic devices because it shows high biocompatibility and high stability in air and in aqueous environment, its surface conductivity may be thinly controlled and it exhibits the highest grafting stability [1]. Generally, bio-molecules are immobilized on the diamond surface through small cross-linkers which covalently bond those molecules to the inorganic diamond substrate. Among the cross-linkers, the amino groups are the more favourable. Thermal, chemical, photochemical and electrochemical surface modification are used to graft the amino-groups on diamond surface[2]. This modification usually involves two or more steps with potential increase of surface contamination. For this reason, one-step amination of H-NCD surface using UV irradiation in an ammonia gas was recently proposed [3]. In this work we present an XPS in situ investigation of the one-step amination with the aim to better understand the chemistry behind the grafting and in particular the role of oxygen.