Nanoscale structure, composition, and charge transport analysis of transparent conducting oxide nanowires written by focused ion beam implantation

Realizing optically transparent functional circuitry continues to fuel scientific and technological interest in transparent conducting oxides (TCOs). However, precise means for creating transparent interconnects for device-to-device integration has remained elusive. Here we report on the chemical, microstructural, and electronic properties of transparent conducting oxide nanowires (Ga-doped In₂O₃) created by direct-write focused ion beam (Ga⁺) implantation within an insulating oxide substrate (In₂O₃). First, methodology for preparing TEM-ready samples is presented that enables detailed TEM-based analysis of individual nanowires. Differences in diffraction features between doped and undoped oxide regions, accompanied by RTA results, support a model in which oxygen vacancies and amorphization comprise the predominant doping/carrier creation mechanism. The same isolated nanowires are then subjected to chemical profiling, providing quantitative information on the lateral Ga doping dimensions, which are in good agreement with conductive AFM images. Furthermore, spatially selective nanoscale EELS spectroscopy provides additional evidence for changes in the oxygen site chemical environment in the FIB-processed/doped In₂O₃, and for negligible changes in the surrounding non-FIB-processed/undoped oxide. The nanowires exhibit ohmic electrical behavior and with an average estimated conductivity of 1600-3600 S cm^-1, similar to macroscale Ga-doped In₂O₃ films grown by conventional processes.