SEMICONDUCTING PROPERTIES OF THE ANODIC PB(II) OXIDE FILM IN ALKALINE-SOLUTION

The semiconducting properties of the anodic film formed on Pb in 0.1 M NaOH solution (60 degrees C) at 0.2 V (vs. Hg/HgO) have been investig ated by the ac impedance and photocurrent methods at room temperature. The Mott-Schottky plots show that the anodic film is an n-type semico nductor. Values of flatband potential for the anodic film anodized for 0.5 and 1.0 h are -0.79 and -0.78 V (vs. Hg/HgO), and the correspondi ng values of donor density are 3.73 x 10(16) and 5.42 x 10(16) cm(-3), respectively. The analysis of the photocurrent spectra shows the band gap width of the anodic film for indirect transitions as 1.88 eV. The relation between photocurrent and applied potential for the anodic fi lm has been analyzed by the Gartner model, from which the values of th e absorption coefficients of t-PbO were found to be much larger than t hat of t-PbO single crystals. This may be caused by the extrinsic phot ogeneration of electron-hole pairs.