Fabrication of an Atom Chip for Studying Atom-Surface Interactions.

Using photolithography processes, we have fabricated a chip-based magnetic microtrap (atom chip) suitable for trapping Rb atoms close to a gold surface in order to study atom-surface interactions. The surface, separated from the trapping wires by a polyimide dielectric, also acts as a shield to block out stray electric fields from the wires. The polyimide layer is highly planarizing to minimize surface corrugations, but $<$ 5 $\mu $m thick to attain the high magnetic field gradients required to bring the trapped atoms within 2 $\mu $m of the surface. A lift-off process has been developed to fabricate evaporated gold wires with edge roughness $\sim $100 nm, limited by the grain size of the gold. Results of atom chip performance and trap loading are presented.