Field Emission Current Uniformity and Stability of Well-Aligned Carbon Nanotubes Synthesized in Methanol

Abstract

Field emission current uniformity and the stability of well-aligned carbon nanotubes (CNTs) synthesized in methanol have been evaluated. For the growth of CNTs, a cobalt-loaded silicon substrate was heated by applying a direct current through the substrate in methanol. Well-aligned CNTs were grown vertically on the substrates at temperatures of 600 and 900 C. The uniformity and the stability of field electron emission from the CNTs were measured with a scanning probe field emission current (SPFEC) system. The CNTs grown at 900 C, which had higher crystallinity according to laser Raman spectroscopic analysis than those grown at 600 C, showed excellent uniformity and high stability of the emission current. Over all measured areas of 2 Â 2 mm 2 on the well-aligned CNTs grown at 900 C, a uniform emission current larger than 100 nA was obtained at an anode voltage of 280 V, when the gap from the CNTs to the anode was 30 mm. Emission current stability with a range of 5 to 6 mA at an anode voltage of 300 V was observed in the CNTs grown at 900 C.