Metastable Atom Lithography

Abstract

This thesis describes the development of a rare gas metastable atomic beam apparatus, and its application to atom lithography. The principal component of the apparatus is the supersonic DC discharge source. The source parameters, such as operating pressure, skimmer distance, discharge current and nozzle shape were optimised to generate a bright beam of excited state metastable neon and argon, with typical flux of 5×10¹? atoms sr?¹ and 3×10¹? atoms sr?¹ respectively. This apparatus was used to investigate the pattern formation of self assembled monolayer (SAM) resists prepared on Au/Si samples exposed to metastable beams of Ar* and Ne*, through microfabricated contact masks. Positive and negative tone patterning was observed, with supporting XPS analysis attributing the negative tone resists to contamination from pump oil vapour. The formation of negative tone contamination resists by the metastable neon beam was applied to the generation of micrometer sized Fe structures using contact masks. A 3-step etch process was developed and refined, resulting in 7.5µm Fe microdot structures on a Si substrate. A bright transverse and longitudinally cooled and collimated metastable neon beam source for atom lithography was developed. The transverse atomic beam collimation stage produced a collimated beam flux of of 1.4×10¹? s?¹, with a divergence of 22.8 mrad. Axial slowing of the atomic beam was demonstrated with the development of a Zeeman slower. Numerical simulations were undertaken to calculate the motion of metastable neon atoms in a one-dimensional standing wave light field mask. The simulations show the dynamics and atom distributions for the focusing regime (low power) and channeling regime (high power). Future refinements of the apparatus should allow the realisation of nanofabricated structures utilising optical masking techniques.