Title : Electrostatically induced flexovoltage in silicon–platinum junctions
Abstract:
Improvements in the tools available to probe charge transport at the nanoscale have been behind many recent advances in electronics, energy conversion, and storage technologies. Despite the broad adoption in nanoscience of atomic force microscopy (AFM) based electrical measurements, such measurements still face technical and conceptual challenges, such as hard-to-minimize, and often bias-dependent, tip drift and tilt. 1 This talk will present findings with immediate implications for analyzing AFM-based current–voltage spectroscopy at silicon surfaces. We show that at silicon electrodes protected from anodic degradation by a self-assembled monolayer, 2 there are voltage-dependent adhesion forces that, provided the current flow is negligible, cause a measurable rotation of the AFM platinum tip. The rotation of the tip is electrostatic in origin and leads to a strain gradient on the silicon which in turn induces an additional reverse bias term (flexovoltage). This “internal” additional bias causes the Schottky diode to leak: a leaky diode in response to continually changing strain gradient due to electrostatic tip–substrate adhesion. These findings highlight the complex interplay of electrostatic effects, mechanical stimuli, and nanoscale friction in AFM-based electrical measurements at semiconductors.
