1-4244-1134-3/07/$25.00 © 2007 129 Field emission observation of carbon nanosheet thin film by photoelectron emission microscopy (PEEM) Kun Hou 1 , Martin E. Kordesch 2 , Uwe Arp 3 , Mingyao Zhu 4 , Ronald A. Outlaw 1 , Peter Miraldo 4 , Brian C. Holloway 1,5 , Dennis Manos 1,4 1 Department of Applied Science, College of William and Mary, Williamsburg, VA 23187-8795 2 Department of Physics and Astronomy, Ohio University, Athens, OH 45701 3 Electron and Optical Division, National Institute of Standard and Technology, Gaithersburg, MD 20899 4 Department of Physics, College of William and Mary, Williamsburg, VA 23185-8795 5 Luna Nanoworks Division, Luna Innovations Incorporated, Danville, VA 24541 * Corresponding author: kxhoux@wm.edu , 757-221-1895 Carbon nanosheets (CNS), a novel-two dimensional carbon nanostructure consisting of vertically oriented ultra-thin graphitic sheets terminating with 1-3 graphene layers, are fabricated by inductively coupled radio frequency plasma enhanced chemical vapor deposition. [1, 2] Carbon nanosheets have been successfully deposited on a variety of substrates such as Si, Al 2 O 3 , SiO 2 , Ti, and Au without the need of catalysts. [3] A representative carbon nanosheet is hundreds of nanometers in length and height but less than 2 nm in thickness, as shown in Fig. 1. Carbon nanosheets, with their atomic-scale edge structure, high purity, and uniform height distribution have been suggested to be a promising candidate for the cold cathode in vacuum microelectronic devices. [4-6] In this study, the field emission characterization of carbon nanosheet thin film was conducted using a diode configuration with an anode-cathode distance of 254 µm. To date, a maximum total current of 26 mA has been measured from a 32 mm 2 testing area at an applied electric field of 25.5 V/µm, as indicated in Fig. 2. Moreover, a stable 19 hour lifetime test at a dc current level of 1.2 mA is presented in Fig. 3. The lifetime test was conducted using a 32 mm 2 test area in a constant 12.5 V/µm electric field. No secular decay of current with time was observed; the variation over 19 hours was less than 2%. Photoelectron emission microscopy (PEEM) was used to investigate the field emission uniformity over the surfaces of carbon nanosheet thin films. PEEM measurements were conducted using a front-gated triode with carbon nanosheets as the cathode, a copper mesh front gate, and the objective lens of the microscope as the anode. The gate-cathode and anode-cathode distance are 125 µm and 4 mm, respectively. We can discriminate PEEM images of the gate from those of the nanosheet film, since these sources yield different kinetic energies in the triode. In addition, FEEM images of the nanosheets, formed without photon illumination, were also captured. The instrument permits quantitative measurement of the total current collected within the field of view of the electromagnetic lens system. The analysis of these images shows that any given time a small number of the numerous possible nanosheet emission sites dominate the emission current. [1] J. J. Wang et al, Applied Physics Letters 85, 1265-1267(2004). [2] J. Wang et al, Carbon 42, 2867-2872(2004). [3] M. Zhu et al, Diamond and Related Materials 16, 196-201(2007). [4] S. Wang et al, Applied Physics Letters 89, 183103-183103(2006). [5] J. Wang et al, Journal of Vacuum Science & Technology B 22, 1269-1272(2004). [6] T. Tyler et al, Journal of Vacuum Science & Technology B 24, 2295-2301(2006). Authorized licensed use limited to: IEEE Xplore. Downloaded on January 23, 2009 at 10:45 from IEEE Xplore. Restrictions apply.