Fig. 2: The disordered regions modified by the ion beam have suppressed surface conductivity.

A Schematic of the AFM configuration showing how current and topography is measured over a patterned region. B Mapping of surface currents of a Sb₂Te₃ single crystal showing that the 3 × 3 rectangular grid sections, which were modified by the ion beam, are less conducting. Each square received a sequentially increasing ion beam fluence from low dose (top right square) to high dose (bottom left square) ranging from 3.74 × 10¹³ ions/cm² to 1.12 × 10¹⁶ ions/cm² (see Supplementary Information for the details) The measurement bias was 2.5 V. C Height map over the same region as in (B) showing that topography is modified for higher fluences. D Integrated current and height of each Sb₂Te₃ grid point irradiated with increasing dose of Ga⁺ ions, measured using cAFM with a scanning bias of 2.2 V. E Current mapping using a 1 V DC bias for an individual irradiated box (see Supplementary Information for IV characterization) showing additional conductivity at the edges of the pattern, and on surface terraces. F Four-probe temperature-dependent resistance of a Sb₂Te₃ device before and after amorphization, showing the increased resistance. The inset shows the measurement configuration.