Structures of $\sim 100$ nm Size Produced by Atom Lithography with Metastable He

We have used neutral atom lithography with metastable 2$^3$S He (He*) to produce structures of size $\sim 100$ nm. A beam of He* from our source is collimated by the bichromatic force\footnote{M. Partlow et al., Phys. Rev. Lett. {\bf 93,} 213004 (2004)} and then by optical molasses. Atoms cross a standing wave of $\lambda =$ 389 nm light tuned $\sim$80 MHz below the 2$^3$S$_1 \rightarrow 3^3$P$_2$ transition and are focussed into lines striking a self assembled monolayer (SAM) of nonanethiol coated over a gold film on a single crystal Si wafer. The 20 eV internal energy of He* destroys the SAM molecules ultimately leaving a pattern of SAM on the gold. Subsequent etching of the unprotected region of the gold results in these features\footnote{C. Allred et al., submitted to J. Appl. Phys.}$^,$\footnote{C. Allred, Ph.D. Thesis, Stony Brook, NY (2009) - unpublished.}. The lines are separated by 194.5 nm and they occupy about 60\% of their spacing. AFM measurements of our first samples show their width to be $\sim 120$ nm and their depth to be $\sim 10$ nm.