Adsorption of Ba Atoms Influences the Composition, Emission, and Optical Properties of CdS Single Crystals

Abstract

We have studied the composition, electron emission, and optical properties of CdS single crystals covered by a surface film of adsorbed Ba atoms with thickness Θ from 0.5 to 5 monolayers (ML). It is established that, as Θ increases up to 1 ML, yield depth λ of true secondary electrons (and photoelectrons) in the emission zone exhibits significant growth, which is explained by decreasing work function of the material surface. The further increase in Θ is accompanied by a decrease in both λ and photocurrent intensity values. It is found that no significant mutual diffusion of atoms at the Ba-CdS interface takes place at room temperature. Upon heating to T = 700 K, sulfur atoms exhibit intense diffusion into the Ba film and form a surface compound of the Ba 2 S type.