Electrical properties of semiconductor CdS studied by adsorption spectroscopy

Abstract

The electrical conductivity of semiconductor CdS films (d ≤ 1 μm) having (0001)S and (0001)Cd polar faces has been measured as a function of temperature at different degrees of adsorption of O₂, NO₂, and N₂O molecules. Adsorption spectroscopy has been used to identify bulk and surface electronic centers in a series of states with a wide range of ionization energies: E_t = 0.14–2.21 eV. In contrast to the bulk centers, which have a quasi-continuous energy spectrum characteristic of CdS, the surface adsorption electronic centers have a discrete energy spectrum. The ionization energy of the electronic centers of adsorption origin in CdS + O₂, CdS + NO₂, and CdS + N₂O structures has been measured for the first time at both polarities of the CdS faces and has been shown to depend on the chemistry of the adsorbate and the polarity of the film face.