Elaboration, Characterizations, and Energetics of Robust Mo6 Cluster-Terminated Silicon-Bound Molecular Junctions

Abstract

Reaction of a [Mo6Br8F6]2– octahedral cluster unit with functional carboxylic acid leads to the formation of the corresponding carboxylate along with the elimination of HF and the formation of a Mo–O bond between the cluster and the carboxylate. This offers an easy way to prepare Mo6 cluster functionalized surfaces by simple reaction of carboxylic acid-modified n-type Si(111) surfaces in a solution of [Mo6Br8F6]2– cluster units. The surface coverage of metallic clusters has been controlled in the range 0.3–5.8 × 1013 cm–2 by dilution of the carboxylic acid-terminated organic chains with inert n-dodecyl chains. The homogeneity of the grafted films on the oxide-free Si surface was followed by combined XPS and STM analyses whereas the electronic gap corresponding to the difference between the conduction band minimum (CBM) and the valence band maximum (VBM) of a single immobilized cluster was determined from tunneling spectroscopy data obtained from a surface with a low cluster coverage. The energy position o...