Preparation and Characterization of Octadecanethiol Self-Assembled Monolayers on Indium Arsenide (100)

Self-assembled monolayers (SAMs) of octadecanethiol (ODT) on InAs(100) were prepared and characterized in detail. The native oxide of InAs was removed by a wet chemical etching method which allows formation of ODT SAMs on bare InAs(100) without any exposure to the ambient atmosphere. Contact angle measurement, ellipsometry, Fourier transform infrared spectroscopy, and atomic force microscopy show that the resulting SAMs are smooth, continuous, and well ordered. X-ray photoelectron spectroscopy confirms bonding of ODT to the substrate as thiolate. When InAs-ODT is exposed to the ambient atmosphere, some reoxidation of the substrate takes place. Thermal stability studies demonstrate that ODT SAMs are completely stable up to 140 °C. Decomposition of ODT occurs above 250 °C.