We have discussed the orientation and chemical state of ethanethiolate on a clean Cu(111) surface adsorbed at 90 K and 300 K. At 90 K, two ethanethiolate (C2H5S-) of different orientation on surface are identified while for adsorption at 300 K, atomic sulfur and only a thiolate are identified to be adsorbed at different adsorption sites. It was found that the tilt angle of the S-C bond at room temperature is larger than that of the thiolate at low temperature. The amount of charge transferred from substrate to molecule is also large for the ethanethiolate at room temperature adsorption. (c) 2006 Elsevier B.V. All rights reserved.