With the highest brilliance synchrotron radiation X-ray (SPring-8) and TEM observations,
Cu oxides ranged 2-nm to 10-nm in thickness formed on sputtered Cu has been evaluated. For the
plasma-assisted Cu oxide, weak Cu2O and/or CuO X-ray diffraction pattern is observed, while no
diffraction pattern in native and thermally (170°C) grown oxides. Those native and thermal oxides
show Cu2O coordination observed by XANES (X-ray Absorption Near Edge Structure) method. This
suggests that Cu oxide formed at low temperatures consists of stoichiometric Cu2O in an amorphous
structure. According to the Fowler-Nordheim (F-N) current emission model, the current emission
taking place at Cu2O decreases with increasing of the oxide thickness and its mean barrier height (φB)
in the MIM band structure. In case of current density at 106A/cm2 of 1V, it is estimated that the
allowable thickness of Cu oxides is approximately 1.5-nm at 1 eV of barrier height.
The valence state of Yb ion in YbInAu2 compound at high pressure determined by x-ray diffraction and x-ray absorption near edge structure measurements