Achieving the In-plane Orientation of Carbon Nanowalls: Implications for Sensing, Energy Harvesting, and Nanobio Devices

High Resolution Image Download MS PowerPoint Slide The in-plane orientation of the nanowalls was successfully realized through control of the ion energy and incidence angle during plasma-enhanced chemical vapor deposition processing of carbon nanowalls (CNWs). The ion energy and incidence angle were controlled by using a tilted stage, a metal mesh, and a radiofrequency (RF) stage bias. The degree of in-plane orientation was strongly dependent on the ion energy and incidence angle. The maximum degree of in-plane orientation was 0.65 for a stage tilt angle of 75° and an RF bias of 6 W. In the in-plane X-ray diffraction pattern, a graphite 002 peak was observed at a diffraction angle of 25.7° only when the X-rays were incident along the in-plane orientation direction of the CNWs. The electrical conductivity of the in-plane oriented CNWs was measured using the four-point probe method, and the in-plane conductivity was determined to be 2.5 times larger than that in the perpendicular direction. The conductivity was also improved by a factor of 2 compared to random CNWs. These results show that control of the degree of in-plane orientation leads to anisotropic electrical properties for vertically grown nanographene.