Scanning Tunneling Microscope Tip-Induced Formation of Bi Bilayers on Bi₂Te₃

We report the formation of Bi(111) bilayer islands and crater structures on Bi₂Te₃(111) surfaces induced by voltage pulses from a scanning tunneling microscope tip. Pulses above a threshold voltage (+3 V) produce craters ∼0.5 µm in diameter, similar to the size of the tip. Redeposited material self-assembles into a network of atomically ordered islands with a lattice constant identical to the underlying Bi₂Te₃ surface. The island size monotonically decreases over several microns from the pulse site, until the pristine Bi₂Te₃ surface is recovered. We assign these islands to Bi bilayer based on atomic resolution images, analysis of step heights, and tunneling spectroscopy. The dependence of bilayer formation on bias polarity and the evidence for defect diffusion together suggest a mechanism driven by the interplay of field evaporation and tunneling-current-induced Joule heating.