Thermoelectric Power of Illuminated CdS

Abstract

The change in the thermoelectric power of CdS under illumination was investigated by Seiter (1) and Weichman et al. (2). Whereas the results of Seiter show a decrease of the thermoelectric power with increasing photoconductivity, Weichman measured an increase with increasing illumination. The theory of the photothermoelectric effect for weak illumination, developed by Tauc (3, 4). predicts a decrease of the thermoelectric power with increasing conductivity. An extension of that theory to the case of strong illumination by Weichman (2) gives the same result.We measured the dependence of the thermoelectric power on photoconductivity of CdS single crystals grown by the Frerich method, at room temperature. The dark conductivity was lower than 10In cm (dark carrier concentration < 5x10 ~m -~) . The electron concentration was changed from 10 to 1013 cm ing to a change of the sample resistance from 1 0 l 1 to 10 a. In order to resolve changes of the thermoelectric power of 2 2 pV/ C even for a source resistance of 10 a compensation method using a vibrating capacitor electrometer (Keithley 640). All connecting leads were shielded rigorously (5). The crystal was contacted with indium and could be illuminated simultaneously by bandgap and infrared radiation.

Magnetic Susceptibility of Semiconducting and Metallic FeSi2

“…The deneity of states, N, This means that every iron atom donates two electrons into the 3d conduction band of the metallic phase which is in agreement with (1). The value of N determined by magnetic measurements is more certain than that from electric data since the mobility does not enter into equation (1).…”