Ceramics-Silikáty 54 (1) 19-25 (2010)

STRUCTURAL AND ELECTRONIC PROPERTIES OF ELECTRODEPOSITED HETEROJUNCTION OF CuO/Cu2O

R. P. Wijesundera, M. Hidaka, K. Koga, J.-Y. Choi, N. E. Sung

The structures and the electronic band states of the electrodeposited thin film CuO/Cu₂O heterojunction have been studied by means of the X-ray diffractions (XRD) and the X-ray absorption spectra (XAS) with different grazing angles of the incident X-ray beam using the synchrotron radiation. The heterojunction of about 2 μm consists of n-type Cu₂O (~1 μm) and p-type CuO (~1 μm) thin films bi-layer. Scanning electron micrographs (SEMs) show the existence of two different polycrystalline grain layers and the XRD reveals that the different grain layers are high quality CuO-type and Cu₂O-type structures respectively. Photoactive performances of the Ti/CuO/Cu₂O/Au heterojunction are V_oc of ~210 mV and J_sc of ~310 mA/cm². It reveals that the Cu₂O grains are grown from the surfaces of the CuO polycrystalline grains and make very good contact with the CuO grains. It is found that the XAS of CuO/Cu₂O heterojunction are convoluted independently by X-ray absorption fine structure (EXAFS) and X-ray absorption near edge structures (XANES) spectra of the Cu₂O and CuO grains, depending on the grazing angles. Present study reveals that bottom of the conduction band (Cu-4pp) of the Cu₂O in the CuO/Cu₂O heterojunction reduces by 0.57 eV relative to the Ti/Cu₂O ohmic contact.

Keywords: Electrodeposited thin films, CuO/Cu₂O heterojunction, Structure, Electronic band states