Nanoscale crystallization of Cr2Ge2Te6 thin films induced by terahertz near-fields

Cr2Ge2Te6 (CrGT) is a promising phase-change material exhibiting low operating energy and a thermally stable amorphous phase, suitable for next-generation nonvolatile memory. To assess its nanoscale switching behavior, we investigated phase transitions in amorphous CrGT thin films using a scanning tunneling microscope excited by picosecond terahertz (THz) pulses. Local THz near-fields enhanced within the tunnel junction induced reproducible nanoscale crystallization without mechanical contact. By varying the field strength, we identified a threshold far-electric field of approximately 0.6 kV cm−1 for the onset of crystallization. The results indicate that Joule heating generated by the tip-enhanced THz near-field governs the amorphous-to-crystalline transition. These findings establish THz field-driven nanoscale phase switching in CrGT and provide a physical framework for ultrafast, nonvolatile phase-control architectures.