Neutral Atom Lithography Using a Bright Metastable Helium Beam

We have performed neutral atom lithography using a beam of metastable 2$\,^3$S Helium (He*) that is brightened sequentially by the bichromatic force and then optical molasses\footnote{M. Partlow et al., Phys. Rev. Lett {\bf 93}, 213004 (2004).}. We have successfully demonstrated this technique using a physical mask of fine mesh covering a self assembled monolayer (SAM) of nonanethiol over a 20 nm evaporated film of Au on a Si wafer substrate\footnote{Younan Xia et al. Chem. Mater. {\bf 7}, 2332 (1995)}. The 20 eV internal energy of He* damages the SAM so that those damaged molecules and the underlying Au layer can be removed using a wet chemical etch$^5$. Samples created this way have an edge resolution of $\sim \,$63 nm that we measured with an atomic force microscope. This technique has promise for creating nano-structured meta-materials with unusual optical properties.