Schottky nanocontact on single crystalline ZnO nanorod using conductive atomic force microscopy

Abstract

This article reports the formation of Schottky nanocontacts on single crystalline ZnO nanorods (NR) using atomic force microscopy (AFM) with a PtIr-coated Si cantilever in a contact mode. ZnO NRs were synthesized by thermal evaporation of metallic zinc thin film followed by annealing. The NRs are [11 $$ \overline{2} $$ 0] directed (i.e., along a-axis) which is quite unusual for wurtzite ZnO. The appearance of an intense visible emission band in room-temperature photoluminescence indicates the presence of a high density of intrinsic defects confirming n-type ZnO. The PtIr tip/ZnO Schottky nanocontacts with an ultra fine effective contact radius ~0.5 nm on horizontally dispersed NRs show an ideality factor of ~7, turn on voltage of ~1.0 V, Schottky barrier height of ~0.65 eV, breakdown voltage of ~−4.7 V, and ON to OFF current ratio of ~500 at ±2 V. The junction corresponds to a nanoscale Schottky contact with satisfactory properties which is comparable to the other PtIr/ZnO or Pt/ZnO reports at higher loading forces. Single crystallinity and contact on the side faces of the horizontally dispersed NRs are primarily thought to be the key factors for higher device performances.