By exposure to a metastable helium beam, latent images of the patterns were formed in the heptanethiol (HT) self-assembled monolayer (SAM) resists on Au(1 1 1) films, and then the patterns were transferred to the underlying gold films by wet chemical etching. Negative patterns, as well as positive patterns with lower doses, were fabricated with higher exposures to a metastableatom beam. The smallest width of edge, similar to40 nm, among alkanethiol SAM resists was achieved in the condition of negative pattern formation. According to the metastable-atom-stimulated desorption (MSD) measurement of alkanethiol SAMs on Au(I 1 1), the SAMs were damaged under the irradiation of metastable-atom beam losing either H atoms or CH3 groups. Thus, the highly concentrated energy deposition by a metastable-atom beam, which induced crosslinking of the main molecular chain in the SAM resists and increased the resistance to etching, could lead to the negative pattern formation at higher doses. (C) 2004 Elsevier B.V All rights reserved.