Direct-write fabrication of a nanoscale digital logic element on a single nanowire

Abstract

In this paper we report on the ‘direct-write’ fabrication and electrical characteristics of ananoscale logic inverter, integrating enhancement-mode (E-mode) and depletion-mode(D-mode) field-effect transistors (FETs) on a single zinc oxide (ZnO) nanowire.‘Direct-writing’ of platinum metal electrodes and a dielectric layer is executed onindividual single-crystalline ZnO nanowires using either a focused electron beam(FEB) or a focused ion beam (FIB). We fabricate a top-gate FET structure, inwhich the gate electrode wraps around the ZnO nanowire, resulting in a moreefficient gate response than the conventional back-gate nanowire transistors. ForE-mode device operation, the gate electrode (platinum) is deposited directly ontothe ZnO nanowire by a FEB, which creates a Schottky barrier and in turn afully depleted channel. Conversely, sandwiching an insulating layer between theFIB-deposited gate electrode and the nanowire channel makes D-mode operation possible.Integrated E- and D-mode FETs on a single nanowire exhibit the characteristics of adirect-coupled FET logic (DCFL) inverter with a high gain and noise margin.