Abstract
CdSe electrodes dip-treated in 10 mM AgNO 3 solution behave almost as a silver electrode because the CdSe/Ag interface has ohmic characteristics. On the other hand, CdSe electrodes modified by vacuum evaporation of silver and then heat-treated in a He atmosphere showed negligible dark currents in the anodic potential region. Cathodic as well as anodic photocurrents were observed at this electrode. The electrode was relatively stable and although the anodic photocurrent at this electrode was initially much smaller than the anodic photocurrent at the unmodified CdSe electrodes, it became larger than the anodic photocurrent observed at the unmodified electrode after illumination for 1000 s. A quite unusual quantum efficiency action spectrum was obtained at this electrode. A very sharp peak around 725 nm, a low but constant quantum efficiency in the shorter wavelength region and an extended response to sub-band illumination were observed. These results suggest the formation of a surface layer with many impurity levels. AES and XPS depth profiling show that Ag diffuses deeper into the CdSe substrate than several tens of nanometers. The XPS study also suggests that Ag exists as Ag(0) in this layer. The junction characteristics of Au/CdSe and Au/CdSe(Ag) show that this layer has a very high resistance. PL measurements proved the introduction of high density impurity levels within this layer. On the basis of these results, a band model is presented for this electrode.
Published Version
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