Narrow bandgap Cu2 O films of p- and n-type conductivities are electrodeposited on conducting glass substrates from aqueous Na2 SO4 solutions. These Cu2 O films exhibit photoelectrochemical responses under visible light illumination. The p- and n-type films have different preferred out-of-plane orientations of  and , respectively. X-ray absorption fine structure spectroscopic analysis shows that the n-type Cu2 O contains a higher degree of lattice disorder. Ultraviolet photoelectron spectroscopy along with the Mott-Schottky electrochemical impedance analysis determines the energy-level diagrams of both the p- and n-type films. On the basis of the structural features obtained, this paper finds that strong Cu2+ absorption on the unstable surface states resulting from the Cu vacancies of Cu2 O can lead to the formation of an inversion layer and thus conductivity transition from p to n type. As a consequence of this p-n transition mechanism, Cu2 O films containing nanocavities for strong Cu2+ absorption exhibit an n-type conductivity, while intact Cu2 O films are p type. A conductivity-type diagram is constructed to show that a subtle change in the deposition parameters can tune the crystal orientation and conductivity type of Cu2 O films.
All Science Journal Classification (ASJC) codes
- Electronic, Optical and Magnetic Materials
- Renewable Energy, Sustainability and the Environment
- Surfaces, Coatings and Films
- Materials Chemistry