Alkanethiolate Self-Assembled Monolayers As a Negative or Positive Resist for Electron Lithography

Taking self-assembled monolayers (SAMs) of octadecanethiol (ODT) on Au(111) as a test system, we demonstrate that aliphatic SAMs can serve as both positive and negative resist materials for electron-beam lithography. This is a principally new finding, since these systems are generally considered as positive resists only and no negative resist behavior has been reported so far. The behavior of the SAM resist was found to be dependent on the irradiation dose and explained by the dominance of different irradiation-induced processes at different stages of electron-beam treatment. A negative resist performance was only observed at low irradiation doses. The transition from the negative to positive resist behavior occurred at 8−10 mC/cm 2 (50 eV electrons) under the conditions of our experiments.