Organopalladium molecules, such as Pd(CH3COO)(2) ({Pd}), immobilized on the S-terminated GaAs(001), termed GaAs-S-{Pd} have high catalytic activity and cycle durability in the Mizoroki-Heck reaction. It is thought that the presence of Ga-S bonds in the single atomic layer S-termination is essential for these catalytic properties despite the much higher thickness (similar to 100 nm) of the {Pd} films. In this study, the authors demonstrate the retention of Ga-S bonds in ultrathin GaAs-S-{Pd} by using reflection high-energy electron diffraction and scanning tunneling microscopy (STM). The ultrathin GaAs-S-{Pd} was prepared by using a vapor-deposition technique. Deposited {Pd} was observed as similar to 1 nm dotlike structures with STM. The adsorption rate of {Pd} was also investigated. (C) 2009 American Vacuum Society. [DOI: 10.1116/1.3193687]