Materials analysis and focused ion beam nanofabrication of topological insulator Bi₂Se₃

Focused ion beam milling allows manipulation of the shape and size of nanostructures to create geometries potentially useful for opto-electronics, thermoelectrics, and quantum computing. We focus on using the ion beam to control the thickness of Bi₂Se₃ and to create nanowires from larger structures. Changes in the material structure of Bi₂Se₃ nanomaterials that have been milled using a focused ion beam are presented. In order to characterize the effects of ion beam processing on the samples, we use a variety of techniques including analytical transmission electron microscopy and atomic force microscopy. The results show that while part of the material remains intact after shaping, amorphous regions form where the beam has been used to thin the sample. For wires created by thinning the material down to the substrate, the sidewalls of the wires appear intact based on diffraction images from samples cut at an angle, but thin crystalline regions remain at the wire edges. Even with the resulting defects and limitations when thinning, focused ion beam milling can be used to fabricate custom geometries of Bi₂Se₃ nanostructures.