AVS 49th International Symposium
    Processing at the Nanoscale Thursday Sessions
       Session PN-ThA

Paper PN-ThA7
Field Emission from Well-Aligned Heterojunctions of Carbon Nanotubes and Silicon Nanowires

Thursday, November 7, 2002, 4:00 pm, Room C-109

Session: Charged Particle Patterning and Emission
Presenter: M. Lu, Lanzhou University, P.R. China
Authors: M. Lu, Lanzhou University, P.R. China
M.-K. Li, Lanzhou University, P.R. China
H.-L. Li, Lanzhou University, P.R. China
Correspondent: Click to Email
Silicon nanowires (SiNWs) has recently attracted much attention due to its unusual properties. However, it is easily oxidized in air, which can hurt the uniformity and the efficiency of electron emission. It is our motivation to design nanowire/tube growth process and fabricate well-aligned CNTs/SiNWs heterojunctions by chemical vapor deposition (CVD) based on AAO template-synthesis method.@footnote 1@ It is clearly observed from SEM and TEM images the junctions consist of a core-sheath structure and have a highly-orientation. The filling material is proved to be a polycrystalline Si from SAED pattern. Field emission measurements show the turn-on field of the junctions decreases to ~7 V/µm from ~14 V/µm (pure SiNWs) and the maximum emission current density increases to ~35 mA/cm@super 2@ from ~3 mA/cm@super 2@ (pure SiNWs). A significant improvement in the turn-on field, the total emission current and the emission stability is apparent from the junctions compared with pure SiNWs. We also notice that the threshold field is in the range of 22-25V/µm for the junctions. The Fowler-Nordheim plot almost follows a linear relationship that indicates the field emission from the junctions is a barrier tunneling, quantum mechanical process. Moreover, the field emission increased with decreasing diameter of the junctions. During 24 h of continuous operation at 5 mA/cm@super 2@, the current fluctuation was as low as ±4% and the average current did not decrease over this period. When a sample was found to air for weeks after it was grown, it exhibited essentially the same emission behavior as the freshly grown surface. This suggests that the sheath of CNTs is indeed stable and chemically inert. @FootnoteText@ @footnote 1@, C.W. Wang, M.K. Li, and H.L. Li, Science in China 44(2), 234 (2001)