文摘
We present a study of the growth and thermal stability of hexanethiol (C6) films on GaAs(110)by direct recoil spectroscopy with time-of-flight analysis. We compare our results with the better knowncase of C6 adsorption on Au(111). In contrast to the two-step adsorption kinetics observed for Au surfacesafter lengthy exposures, data for C6 adsorption on the GaAs(110) surface are consistent with the formationof a single dense phase of C6 molecules at lower exposures. On the contrary, in solution preparation,dense phases can only be obtained on GaAs for long alkanethiols and after lengthy immersions. The C6layer has a first desorption peak at 325 K, where partial desorption of the alkanethiol molecules takesplace. Fits to the desorption curves result in a 1 eV adsorption energy, in agreement with a chemisorptionprocess. Increasing the temperature to 500 K results in the S-C bond scission with only S remaining onthe GaAs(110) surface. The possibility of forming dense, short-alkanethiol layers on semiconductor surfacesfrom the vapor phase could have a strong impact for a wide range of self-assembled monolayer applications,with only minimal care not to surpass room temperature once the layer has been formed in order to avoidmolecular desorption.
