A large-area gold patte with nanoscale edge on muscovite mica was fabricated by using a metastable helium beam and octanethiol(OT)and dodecanethiol(DDT)self-assembled monolayers(SAM),in which the width of edge was typically ～70nm for the OT SAM and ～90nm for the DDT SAM,respectively.The mask was reproduced with high fidelity.Combined the analysis of roughness with grain size,more flat surface and sharper edge of pattes were obtained by using the shorter chain molecules such as the OT.All the information indicated that the OT SAMs on atomically flat surfaces can be used as a resist for exposure to metastable atom beams.