Thiol self-assembled monolayers (SAMs) on gold surfaces have a wide range of applications including surface patterning and metal contact-organic semiconductor interface modification in organic electronic devices. Here we present our studies about the low coverage phases of decanethiol (CH3(CH2)(9)SH) SAMs on Au(1 1 1) surface, grown in vacuum by supersonic molecular beam deposition. Crystal structures, phase behaviors and desorption energies of these films determined by helium atom diffraction technique are discussed. (C) 2013 Elsevier B. V. All rights reserved.