Oriented self-assembled monolayers of bifunctional molecules on InAs

We describe the formation and characterization of oriented self-assembled monolayers (SAMs) of bifunctional molecules on InAs. Cysteamine, a small molecule with thiol and amine termini, can be efficiently deposited on InAs(001) from a basic aqueous solution. Analysis of the deposited films using X-ray photoelectron spectroscopy (XPS) reveals that cysteamine forms a monolayer, in which molecules are oriented and attached to the InAs surface exclusively via their thiol termini. The free amine ligands presented at the interface of the resulting oriented SAM should provide a convenient pathway for subsequent surface functionalization. In addition, cysteamine deposition efficiently removes InAs native oxides; the resulting cysteamine SAM provides surface passivation, protecting the InAs substrate from reoxidation after short-term exposures to air and aqueous solutions.