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Unformatted text preview: Nanoscale Structure, Composition, and Charge Transport Analysis of Transparent Conducting Oxide Nanowires Written by Focused Ion Beam Implantation Norma E. Sosa, Christopher Chen, Jun Liu, Sujing Xie, Tobin J. Marks,* ,, and Mark C. Hersam* ,, Department of Materials Science and Engineering and the Materials Research Center, Northwestern Uni V ersity, 2220 Campus Dri V e, E V anston, Illinois 60208-3108, and Department of Chemistry and the Materials Research Center, Northwestern Uni V ersity, 2145 Sheridan Road, E V anston, Illinois 60208-3113 Received October 30, 2009; E-mail: firstname.lastname@example.org; email@example.com Abstract: 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 In 2 O 3 ) created by direct-write focused ion beam (Ga + ) implantation within an insulating oxide substrate (In 2 O 3 ). 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 spectros- copy provides additional evidence for changes in the oxygen site chemical environment in the FIB-processed/ doped In 2 O 3 , 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 In 2 O 3 films grown by conventional processes. 1. Introduction The implementation of transparent oxides as the basis for all-transparent electronic circuitry has attracted great interest as a driver in both scientific and consumer electronics. 1- 8 The required transparent oxide (TO) materials suite must necessarily include transparent conducting oxides (TCOs), transparent oxide semiconductors (TOSs, which are not degenerately doped in contrast to their TCO counterparts), and transparent oxide insulators (TOIs). This range of electrical properties, combined with optical transparency, renders this materials family uniquely suitable to serve as the foundation for all-oxide electronics....
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