Understanding the Assembly of π-Conjugated Dithiol Molecules on GaAs

Introduction The assembly of alkane-based molecular layers on metals (e.g. Au, Ag, Pt) and, to a smaller extent, on semiconductors (e.g. GaAs, Si) has been investigated in detail. Such chemistries, although potentially valuable in surface engineering and patterning, cannot facilitate charge transport on the molecular level due to their backbone saturation. On the other hand, π-conjugated systems are capable of intramolecular charge transport and are therefore potential candidates for molecular wires and electronic devices whose electrically-active component consists of a single molecule. Assembly of such molecules, however, has been challenging and not thoroughly investigated. Here, we report solvent and substrate effects on the assembly of n-phenyldithiols (n = 3, 4). The coverage and the average molecular orientation on Au are not sensitive to solvent composition. In sharp contrast, the quality of the molecular assembly on GaAs varies drastically with solvent type.