Influence of grain boundaries and interfaces on the electronic structure of polycrystalline CuO thin films. Issue 6 (22nd February 2016)

• Record Type: Journal Article
• Authors: Morasch, Jan; Wardenga, Hans F.; Jaegermann, Wolfram; Klein, Andreas
• Is Part Of: Physica status solidi. Volume 213:Issue 6(2016:Jun.)
• Page Start: 1615
• Page End: 1624
• Publication Date: 2016-02-22
• Subjects: CuO -- Electrical properties -- electronic structure -- magnetron sputtering -- polycrystalline materials -- thin films; Solid state physics -- Periodicals; Solids -- Industrial applications -- Periodicals; 530.41
• DOI: 10.1002/pssa.201533018
• Languages: English
• ISSNs: 1862-6300

Abstract

Abstract: CuO thin films were grown by reactive magnetron sputtering and analyzed with respect to their structural, chemical, optical, and electrical properties. The films are strongly p‐type with carrier concentrations of ∼ 10 20 cm −3 . Carrier accumulation at grain boundaries is evident from temperature and gas phase dependent conductivity measurements. The films show high absorption coefficients with a band gap of approximately 1.5 eV. Interface formation with TiO2 and Au was studied by photoelectron spectroscopy. Regarding the TiO2 /CuO interface, a strong band bending in the TiO2 substrate and a valence band offset of ∼ 2.4 eV were observed. The TiO2 conduction band is therefore approximately midgap of CuO at the interface. CuO is chemically reduced upon Au deposition but an ideal ohmic contact is formed with a Fermi level at the valence band maximum of CuO. Solar cell device structures were prepared of fluorine‐doped SnO2 /TiO2 substrates and Au back contacts, revealing open circuit voltages of <0.15 V and photocurrent densities of <0.1 mA/cm 2 . The photoactivity of the structures is ascribed mostly to the TiO2 substrate.