Ion-Induced Lateral Damage in the Focused Ion Beam Patterning of Topological Insulator Bi2Se3 Thin Films

Focused Ion Beam patterning has become a widely applied technique in the last few decadesin the micro- and nanofabrication of quantum materials, representing an important advantage interms of resolution and versatility. However, ion irradiation can trigger undesired effects on the targetmaterial, most of them related to the damage created by the impinging ions that can severely affectthe crystallinity of the sample, compromising the application of Focused Ion Beam to the fabricationof micro- and nanosized systems. We focus here on the case of Bi2Se3, a topological material whoseunique properties rely on its crystallinity. In order to study the effects of ion irradiation on thestructure of Bi2Se3, we irradiated with Ga+ ions the full width of Hall-bar devices made fromthin films of this material, with the purpose of inducing changes in the electrical resistance andcharacterizing the damage created during the process. The results indicate that a relatively high iondose is necessary to introduce significant changes in the conduction. This ion dose creates mediumrangelateral damage in the structure, manifested through the formation of an amorphous region thatcan extend laterally up to few hundreds of nanometers beyond the irradiated area. This amorphousmaterial is no longer expected to behave as intrinsic Bi2Se3, indicating a spatial limitation for thedevices fabricated through this technique.