We report on the formation of organosilane-, carboxylic acid- and thiol-based self assembled monolayers (SAMs) on two lots of commercially prepared Indium Tin Oxide (ITO) thin films. Contact angle measurements, electrochemical experiments, and near-edge x-ray absorption fine structure (NEXAFS) spectroscopy showed that the quality of monolayers formed differ substantially between the two ITO batches. Only one of the two ITO substrates was capable of forming well-organized (thiol- and carboxylic acid-based) SAMs. In order to rationalize these observations, atomic force microscopy (AFM) and x-ray diffraction (XRD) analyses were carried out, and SAMs were prepared on ITO substrates prepared by sputtering in our laboratories. An attempt was made to influence the film microstructure and surface morphology by varying substrate temperatures during ITO deposition. Good quality thiol and carboxylic acid SAMs were obtained on one of the ITO substrates prepared in house. While our characterization could not single out one specific parameter in ITO surface structure that could be responsible for good SAMs formation, we could point out homogeneous surface morphology as a relevant factor for the quality of the SAMs.
Citation: Journal of Physics D-Applied Physics
Pub Type: Journals
ITO, NEXAFS, surface structure