Effect of nitrogen on valence states of Cu in CuxO by changing the surface chemical potential of oxygen

Because the valence state of metal with variable valences is sensitive to oxidation atmosphere, it is difficult to fabricate single-phased metal oxide with intermediate valence by vapor or vacuum deposition. In this work, the copper valence state in oxides was controlled by introducing a nitrogen flow into the sputtering chamber. The surface chemical potential of oxygen can be efficiently tuned through adsorption competition on the growth surface. The transition process from CuO–Cu₂O mixture to single Cu₂O was observed with increasing the nitrogen flow rate. For the single-phased Cu₂O, the hole concentration was tuned in a range of 2.6 × 10¹⁷ to 1.1 × 10¹⁸ cm⁻³.