场发射材料的演进.pptVIP

* Geometry and structure of CNTs Radius of curvature ~ nm Tube lengths can be mm Field enhancement b1000 Structure MWCNT SWCNT DWCNT Nanohorn * Straight and entangled CNTs * Aligned and patterned CNTs * Patterned CNTs * Single CNT on top of Si tip * Typical I-V and FN plots of CNT emitter Turn-on field can be 3 MV/m * Typical field emission properties of CNTs Key parameter Typical Best Current density CNT film 100 mA cm-2 ~ 1 A cm-2 3 A cm-2 Current density Single CNT 105 107 Turn-on field (MV/m) 1.0 0.6 Threshold field (MV/m) 6 5 Emission site density (cm-2) ~105 108 Turn-on: 10 mA cm-2 Threshold: 10 mA cm-2 * CNTs from polymers S Jou et al, NTUST * Instability of field emission of CNTs with time release of absorbate * Gated CNT emitters * Various nanomaterials for field emission Wide band-gap Narrow band gap Metallic SiC, SiCN, BCN, AlN ZnO GaN, MoO3 …. Cu2S, CuO, MoS2 Mo, W, graphite….. * Needle-shaped SiC nanowires * Nanowire arrays MoO2 MoO3 Mo * IrO2 Nanotubes DH Tsai, YS Huang, NTUST (2005) * Composite emitter array with triode structure electrode is made of a mixture of conductive paste and nanomaterials * FED prototype with printable emitter Ag + CNT * Field emission display * CNT lighting element * Thank you 場發射材料的演進 * Outline Field emission Evolution of electron emitters -Spindt cathode Si tip -Diamond cold cathode -Nanotubes Applications * Field emission The principle of field emission is based on the applications of a very high electric field to extract electrons from a metal or a highly doped semiconducting surface. * Field electron emission from a tip NS Xu, SE Huq, MSE R 48 (2005) 47-189 * Fowler-Nordheim equation The phenomenon of field emission is associated with a quantum mechanical tunneling process whereby electrons tunnel through potential barrier under the influence of a high electric field. The current generated by this process is described by the Fowler-Nordheim (FN) equation. * Fowler-Nordheim equation I =