Tip-induced nanoscale engineering of surface potential and conductivity in GeSn alloys

This study investigates the manipulation of the electronic properties of GeSn alloys at the nanoscale by applying electric fields between an atomic force microscope (AFM) tip and the surface of GeSn films grown on Ge/Si substrates. Local changes in work function (WF) and resistivity were observed by Kelvin Probe Force Microscopy and Scanning Spread Resistance Microscopy and were associated with an increased Sn content in the near-surface region within patterns produced by the AFM tip. The effect is explained by the poor stability of GeSn layers, making possible the diffusion of Sn toward the surface, driven by high electric fields near the AFM tip under combined alternating current and direct current biases. The modified regions of GeSn films with increased Sn content exhibit a significant increase in local conductivity and a lower WF, potentially providing a suitable platform for nanoscale electronic devices based on group-IV materials.