Piezotronic Activity Study by AFM Tip (Al) Top Electrode of Single ZnO Nanofiber Deposited on TiNx/c-Si Substrate

Abstract

ZnO nanofibers were synthesized via a hydrothermal method. A single nanofiber was delicately transferred and deposited onto a TiN_x thin film on a silicon substrate to facilitate the investigation of its piezotronic properties. An aluminum-coated atomic force microscope tip was employed in contact mode as a top nanoscale electrode to locally induce bending deformation in the individual ZnO nanofiber. The current–voltage (I–V) characteristics recorded between the top atomic force microscope tip electrode and the bottom TiN_x surface exhibited rectifying behavior, indicative of the formation of a Schottky junction upon the application of a minimum bending force of 25 nN by the atomic force microscope tip. This force threshold was necessary to ensure adequate contact between the atomic force microscope probe and the ZnO nanofiber. However, upon exceeding the 25 nN bending force perpendicular to the c-axis, the forward current underwent a substantial reduction, eventually leading to complete suppression of the Schottky junction under further increments in the bending force. Finite element method simulations elucidated the presence of piezoelectric activity within the ZnO nanofiber, which was responsible for the observed attenuation in the forward current. The Cheung–Cheung method was employed to quantify the increase in barrier height at the Schottky junction as a function of the applied bending force.