Thermal annealing effect of alkanethiol monolayers on Au(111) in air

Abstract We present a systematic study on the effect of air annealing on the structures of alkanethiol (CH 3 (CH 2 ) n −1 SH) self-assembled monolayers (SAMs) on Au(1 1 1) with chain length n =7, 10, 18. Partial desorption of the monolayers has been observed by scanning tunneling microscopy (STM) and X-ray photoelectron spectroscopy (XPS) at relatively low annealing temperatures. By increasing the annealing time at appropriate temperatures, the structures of SAMs transform from densely packed ( 3 × 3 )R 30° phase to c (4 3 ×2 3 )R 30° phase, and then slowly to striped (p× 3 ) phases with p =4 and 5. Through the relative carbon content measurement by XPS and the stripe spacing measurement by STM, we propose a different stripe phase structure than those observed for SAMs grown by gas-phase deposition or by vacuum annealed solution-grown samples.