Over the past few weeks, I was trying to optimize the E-beam lithography recipes for making suspended nano junctions with Bi2Se3 nanobelts. There were mainly two challenges : (a) charging effects and related effects on pattern resolution and (b) difficulties in focusing the electron optics as the height measurement on a bare sapphire substrate is not accurate. We found that using a properly adjusted proximity error correction file and opting to use a 20 nm Cr layer on top of the resist stack solves both of these EBL problems. An SEM image of one of the first junctions I made is given below. Although this set of devices from the first batch did not perform as we wanted, with some modifications we hope to do gate-controlled transport measurements on TI-junctions in the coming months.
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