LEED–AES study of the oriented adsorption of tetracyanoethylene on potassium chloride

Abstract

The adsorption state of tetracyanoethylene (TCNE) on the (001) cleavage face of KCl was studied by means of LEED combined with AES. The LEED pattern did not show any change in the arrangement of diffraction spots after the adsorption of TCNE molecules, although variations in their intensities were observed, but the intensity of the AES peak from potassium decreases remarkably on adsorption. It was deduced that four CN groups of each TCNE molecule are located directly over potassium ions specifically while less than one quarter of the chlorine ions are covered by CC groups of TCNE with random orientation. The adsorption state of TCNE on KCl is discussed in relation to the epitaxial nucleation of a crystalline film of a similar compound, such as 7,7′,8,8′-tetracyanoquinodimethane (TCNQ). The surface stoichiometry of KCl crystal before the adsorption was confirmed by AES.