Diamond is the ultimate semiconductor for high power and high frequency applications due to his high breakdown electric field, elevated mobility and the outstanding thermal conductivity. Such properties makes attractive the development of diamond-based MOSFET and Schottky diodes, where the conducting or insulating behaviour of the device is based on the electrostatic control of the band curvature at the metal/oxygen-terminated semiconductor interface. Thus, the election of the metallic material is a fundamental aspect that will govern the device characteristics. Furthermore, the role of the oxide layer contacting over the diamond surface determines key aspects of the I-V characteristics of the related device [1]. In this work, various diamond-oxide interfaces for Schottky power diodes purpose are studied. Zr/diamond and WC/diamond Schottky diodes are nano-characterized by a combination of TEM techniques (including HAADF, HREM and EELS). Such devices are structurally and chemically nano-characterized, allowing to correlate its electrical behaviour [2,3] with the related nano-structure. The latter, evidences a relation between the diamond-oxygen-metal configuration and the electrical response. Finally, electrical, structural and chemical properties are compared as competitor devices in order to show the goodness of the performance.