Electron-induced crosslinking of aromatic self-assembled monolayers: Negative resists for nanolithography

We have explored the interaction of self-assembled monolayers of 1,1'-biphe nyl-4-thiol (BPT) with low energy electrons. X-ray photoelectron, infrared, and near edge x-ray absorption fine structure spectroscopy showed that BPT forms well-ordered monolayers with the phenyl rings tilted similar to 15 d egrees from the surface normal. The films were exposed to 50 eV electrons a nd changes were monitored in situ. Even after high (similar to 10 mC/cm(2)) exposures, the molecules maintain their preferred orientation and remain b onded on the gold substrate. An increased etching resistance and changes in the infrared spectra imply a crosslinking between neighboring phenyl group s, which suggests that BPT can be utilized as an ultrathin negative resist. This is demonstrated by the generation of patterns in the underlying gold. (C) 1999 American Institute of Physics. [S0003-6951(99)03640-2].