We demonstrate that strong local electric fields generated by a scanning tunneling microscope (STM) tip induce nanoscale structural modifications beneath the surface of bilayer \(\textrm{Ta}_{2}\textrm{NiSe}_{5}\) . Applying voltage pulses with a positive sample bias leads to the formation of depressions at the pulse sites and protrusions at laterally displaced locations along the crystal’s chain direction. Bias-dependent STM imaging and scanning tunneling spectroscopy reveal no measurable change in the surface electronic structure, indicating that the observed height variations originate from structural, rather than electronic, effects. We propose that the electric field drives anisotropic atomic migration within the van der Waals gap, resulting in reversible and directional reconfiguration of subsurface layers. Sequential pulsing further confirms the dynamic nature of this process, allowing local depressions and protrusions to be erased or repositioned. Our findings introduce a mechanism for electric-field-induced subsurface patterning in layered materials, with potential applications in reconfigurable nanoscale devices in van der Waals materials.
