Nanoscale Electronic Inhomogeneity in In2Se3 Nanoribbons Revealed by Microwave Impedance Microscopy

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Abstract
Driven by interactions due to the charge, spin, orbital, and lattice degrees of freedom, nanoscale inhomogeneity has emerged as a new theme for materials with novel properties near multiphase boundaries. As vividly demonstrated in complex metal oxides (see refs 1−5) and chalcogenides (see refs 6 and 7), these microscopic phases are of great scientific and technological importance for research in high-temperature superconductors (see refs 1 and 2), colossal magnetoresistance effect (see ref 4), phase-change memories (see refs 5 and 6), and domain switching operations (see refs 7−9). Direct imaging on dielectric properties of these local phases, however, presents a big challenge for existing scanning probe techniques. Here, we report the observation of electronic inhomogeneity in indium selenide (In2Se3) nanoribbons (see ref 10) by near-field scanning microwave impedance microscopy (see refs 11−13). Multiple phases with local resistivity spanning 6 orders of magnitude are identified as the coexistence of superlattice, simple hexagonal lattice and amorphous structures with ∼100 nm inhomogeneous length scale, consistent with high-resolution transmission electron microscope studies. The atomic-force-microscope-compatible microwave probe is able to perform a quantitative subsurface electrical study in a noninvasive manner. Finally, the phase change memory function in In2Se3 nanoribbon devices can be locally recorded with big signals of opposite signs.
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