Feedback-controlled ion beam sculpting apparatus

We report the design of an ion sculpting instrument that enables the controlled fabrication of nanometer-sized structures in solid-state materials. The instrument employs a beam of kilo-electron-volt argon ions that impinge on a solid-state membrane containing prefabricated structures such as holes, slits, or cavities whose properties are to be modified. By controlling both the ion beam parameters and sample temperature, the instrument can be adjusted to either deliver or remove material from these articulations, for example opening or closing holes of various shapes. The instrument is unique in its use of feedback control for the crafting of structures that define a hole through which a component of the incident ion beam is permitted to pass and be monitored. Electrostatic ion optics refocus ions transmitted unimpeded through the hole, onto a detector capable of registering single ions. The transmission rate is a direct, real-time measure of the transmitting area that is used as a feedback signal to trigger the termination of the ion irradiation process precisely when a desired dimension is obtained. The ions thus serve the dual role of modifying and measuring the size of the nanoscale structures. The sensitivity of the ion beam sculpting apparatus to atomic-scale material rearrangement at the perimeter of a hole also enables the study of ion beam induced material transport at solid-state surfaces. The utility of the instrument as a fabrication tool has been demonstrated by the fabrication of nanopores used for recent single-molecule biophysics studies. (C) 2004 American Institute of Physics.