XPS survey spectra of copper oxide films prepared by reactive magnetron sputtering. The oxygen content in the process gas and substrate temperature TS during deposition are annotated. The emission lines are identified for the topmost spectra. No surface carbon contamination at ∼285 eV binding energy is observed.
Detail XP spectra of the Cu emission, its satellite lines, the O 1s and Cu LMM emissions and the valence band. The films were deposited at RT and various oxygen contents in the process gas, which are indicated in the graphs. Emission features related to Cu(II) are indicated by triangles while metallic Cu is indicated by a circle.
XRD of copper oxide films prepared at different substrate temperature with different oxygen content in the process gas. The expected positions and intensities of Cu2O (PDF-2 card 5-667) and CuO (PDF-2 card 5-937) reflections are indicated.
AFM images of copper oxide samples deposited under 5% oxygen at RT and 500 °C.
Photoelectron spectra of the interface ITO(RT)/Cu2O(RT). The Cu2O film thickness is indicated in nm. Numbers attached to the UP spectra indicate the binding energies of the valence band maxima and the secondary electron cutoff, respectively.
(Color online) Band alignment of the interface between ITO and Cu2O derived from three different interface experiments in the order substrate/film. The calculated from core level binding energies (top) and a schematic representation of the energy diagrams (bottom) are graphically displayed. Values directly obtained from measurements are underlined. All values are given in eV.
(Color online) Band alignment of different interfaces determined using photoelectron spectroscopy. The valence band maximum of Cu2O is used as reference. Using transitivity of valence band offsets, the valence band maximum of Cu2O is expected to be ∼0.2 eV lower than that of Cu2S and ∼0.8 eV lower than that of . The valence band offsets indicated are taken from Ref. 41 (Cu2S/CdS), Ref. 42 (Cu2S/CdS), Ref. 45 (CdS/CdTe), and from Ref. 46 (In3O3/CdTe), respectively. The conduction band minima are calculated bulk energy gaps of 2.1 (Cu2O), 1.2 eV (Cu2O), 1.04 eV (Cu2O), 2.8–2.9 eV (In3O3), 1.49 eV (CdTe), and 2.42 eV (CdS), respectively.
Composition, Fermi level position − , work function , and ionization potential as determined by photoemission from Cu-oxide films deposited by reactive magnetron sputtering with near stoichiometry. Electrical two-point resistances R are given in the last column.
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