화학공학소재연구정보센터
Current Applied Physics, Vol.9, No.2, E29-E32, 2009
Development of scanning field emission current microscopy
Spatial uniformity and durability of field emission are main issues in carbon nanotube (CNT) field emission devices fabricated by a screen-printing process. In this paper, we propose a novel method to visualize field emission sites of CNT films two-dimensionally by adopting scanning probe microscopy. While an anode probe with a small tip diameter of <100 nm was scanned over a CNT emitter surface whose dimension is 200 mu m x 200 mu m, the field emission current was recorded by a Keithley 6517A, SR570 (low-noise current preamplifier) and NI USB-6009 (data acquisition board), converted into 256 grayscale level, and displayed on a monitor through the LabView (TM) program. The anode probe was made by electrochemically etching tungsten wire and the CNT emitter sample was fabricated by screen-printing multiwall CNTs whose diameter is 4-6 nm and length 1-2 mu m on indium-tin-oxide (ITO) glass. During scanning, the gap between W anode and ITO glass surface was maintained to be a few tens of mu m. For large-scale imaging, we used an inertial nano-positioner whose model number is ANPxyz100, made by Attocube Systems, as a long-range scanner. With this system, we could obtain an electron emission current map over large surface areas under constant anode voltage. (C) 2009 Elsevier B. V. All rights reserved.