AVS 47th International Symposium
    Surface Science Tuesday Sessions
       Session SS-TuP

Paper SS-TuP31
Adsorption and Desorption Processes of Alkanethiol Self-Assembled Monolayers on Au(111)

Tuesday, October 3, 2000, 5:30 pm, Room Exhibit Hall C & D

Session: Poster Session
Presenter: J. Noh, Frontier Research System, RIKEN, Japan
Authors: J. Noh, Frontier Research System, RIKEN, Japan
T. Araki, Saitama University, Japan
K. Nakajima, Frontier Research System, RIKEN, Japan
M. Hara, Frontier Research System, RIKEN, Japan
Correspondent: Click to Email
Adsorption and desorption processes of alkanethiol self-assembled monolayers (SAMs) on Au(111) have been examined by scanning tunneling microscopy (STM) and thermal desorption spectroscopy (TDS). New intermediate phases that are expected by a recent diffraction study from coverage-dependant SAMs prepared by a wet process were observed in a molecular level, revealing phase transitions from the striped phase to the upright phase. In addition, surface structure and molecular species desorbing from such SAM samples as a function of surface temperature were monitored by TDS and STM. TDS spectra for dimer molecules as well as alkyl groups formed after cleavage of C-S bond clearly show second-order desorption behavior implying the associative desorption of alkanethiolate adsorbed on Au(111) surface. STM images clearly show structural transitions due to desorption of molecules at elevated surface temperature. Moreover desorption process and stability of pre-covered alkanethiol SAMs in pure solvents at room temperature were investigated. In this study, it is revealed that desorption of alkanethiol SAMs under solvent and UHV conditions initiate at domain boundaries and near depressions that have weaker lateral interactions compared to close-packed domains, followed by desorption of molecules in close-packed domains. From these results, we discuss the adsorption states in alkanethiol SAMs as well as the precise model of the adsorption and desorption processes.