Abstract
By atomic layer deposition, we prepared TiO2 thin films, which do not crack upon thermal treatment at 450-500 °C. The calcination changes the film's work function by tens of meV, as evidenced by electrochemical impedance (Mott-Schottky) and Kelvin probe analyses.
In contrast, the work function of ALD-SnO2 is enhanced by hundreds of meV after this heat treatment. The work function of calcined ALD-SnO2 films is by ca. 0.3-0.4 eV larger than that of the cassiterite single-crystal electrode.
The as-prepared ALD-SnO2 film exhibits significant anodic photocurrent at potentials, when the calcined film is photoelectrochemically inactive. The ALD growth of SnO2 on the Au(111) substrate occurs preferentially at the Au grain boundaries.
In spite of its non-conformal morphology, the Au-supported SnO2 film still blocks perfectly the anodic oxidation of ferrocyanide. Electrochemical doping of ALD-SnO2 by lithium causes a decrease of the work functions by 0.1-0.2 eV in a broad range of film thicknesses.