Electrochemical STM investigation of C70, C60/C70 mixed fullerene and hydrogenated fullerene adlayers on Au(1 1 1) prepared using the electrochemical replacement method

Epitaxial adlayers of (i) fullerene C70, (ii) mixed C60 and C70 molecules, and (iii) hydrogenated fullerene C60Hx(20) on Au(1 1 1) surfaces, were prepared by the electrochemical replacement (ECR) method, and investigated by electrochemical STM observation. The slowness of the iodine desorption and fullerene replacement process controlled by electrochemical potential management in the ECR method, resulted in the formation of high-quality adlayers of fullerenes. In the ECR method, the iodine adlayers promote the high surface diffusion of fullerene and suppress the nucleation of the fullerene array. Not only C60, but also C70, formed highly ordered adlayers when prepared by the ECR method. Moreover, the “standing” orientation of C70 was dominant with respect to the “lying-down” orientation in the ideal C70 hexagonal array on the Au(1 1 1) surface. In addition, the individual features of hydrogenated fullerenes C60Hx(20) in a disordered adlayer were observed for the first time using STM. The potential dependence of the C60Hx(20) adlayer reveals the weaker adsorption of C60Hx(20) rather than the adsorption of C60 and C70.