Adsorption of Ba atoms influences the composition, emission, and optical properties of CdS single crystals

The composition, emission and optical properties of CdS single crystals with a Ba surface film with a thickness of 0.5 to 5 monolayers have been studied. It was found that with an increase in $\Theta$ to 1 monolayer, the depth of the exit zone for true secondary electrons (and photoelectrons) $\lambda$ significantly increases, which is explained by a decrease in the work function. With a further increase in $\Theta$, the values of $\lambda$ and the intensity of the photocurrent decrease. It is shown that at room temperature there is no noticeable interdiffusion of atoms at the Ba–CdS interface. After heating at $T$ = 700 K, intense diffusion of S occurs into the Ba film and a compound of the Ba$_2$S type is formed.