Determining Some Structure-Sensitive Characteristics of Nano-Sized Anodic Ag(I) Oxide from Photopotential Spectroscopy

D. A. Kudryashov, S. N. Grushevskaya, and A. V. Vvedenskii

Voronezh State University, Universitetskaya pl. 1, Voronezh, 394006 Russia

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Received December 1, 2006

Abstract — A relatively simple device involving a set of LEDs and a digital processing of the signal is developed for in situ photopotential and photocurrent spectroscopy of thin semiconductors including oxide films under conditions of discretely changed light wavelength. Decreases in the electrode potential and photopotential of Ag(I) oxide with time upon the anodic effect are shown to obey different kinetic regularities, namely, logarithmic and exponential respectively. Photopotential measurements revealed n-type conductivity in thin (6 to 22 nm) semiconductor Ag₂O films potentiostatically formed on either poly or monocrystalline silver (111) with a band gap of 3.1 eV. The structural disordering of the oxide is minimum at a potential of 0.490 V, which corresponds to nearly a midpoint of the anodic peak shoulder of the voltammogram. The concentration of donor defects in an Ag₂O film grown on a “smooth” polycrystalline silver is lower than that on an ultrafine-dispersed silver, but higher than on Ag(111) monocrystal. A linear dependence of the photoresponse on the light beam power is found, and the spectral dependence of the photopotential is discussed. The photopotential dependence on the film thickness, as well as crystalline and microstructural state of the silver surface means that the photoresponse is determined by the bulk rather than superficial electronic states, and the film thickness is smaller than the Debye shielding length.

PACS numbers: 73.50.Pz, 81.07.-b, 82.45.Cc