Feedback-controlled ion beam system for nanoporous membrane fabrication

We report the design of an ion beam bombardment chamber that enables the controlled fabrication of nanometer-sized holes in solid-state materials. The instrument employs a beam of MeV gold ions that impinges on a polymer membrane whose properties are to be modified. The instrument uses an innovative feedback control for the crafting of structures that define a hole in the film through which a trapped gas is permitted to leak and be monitored by a Residual Gas Analyzer. The polymer thin film was fixed as a cover window to a He gas filled chamber and then exposed to a uniformly scanned gold MeV ion beam masked to define the exposed area. The gas leak rate through the fabricated pores is a real-time measure of the total area of the pores produced and is used as the feedback signal to trigger the bombardment process when the desired nanopore size is obtained. Applications of the instrument, as a fabrication tool for nanopores, have been recently reported for nanoporous membranes studies.