Characterization of material performance of carbon-based field emitters

Summary form only given. The highly enhanced electric field surrounding the microtips on a field emission cathode can induce electron emission by quantum tunneling. Cathodes which generate large currents, such as those used in high power devices, drive a large current through a small microtip. In this paper we examine the Joule-heating of these microtips and their subsequent thermal expansion. Where the base of these heated tips join the cool substrate below, temperature gradients can cause tensile and shearing stresses, which in certain situations may lead to fracture of the microtips. Estimates of the magnitude of these thermomechanical stresses are calculated and compared for examples of micron scale carbon/graphite fiber and carbon nanotube (CNT) field emitters subjected to microsecond pulses of intense electron emission. The work function (phi) of materials utilized in field emission cathodes was investigated computationally using ab-initio quantum mechanical modeling with the Vienna ab-initio simulation package (VASP). This approach enables the detailed and self-consistent treatment of a system based, on quantum mechanical principles, yielding extremely accurate information pertaining to its electronic properties. New insights for the CsI and CsI/graphite system have been obtained and correlated with experimental results obtained from the surface characterization of CsI films thermally evaporated onto graphite substrates. The deposition and growth of thin CsI films on substrates by thermal evaporation comprises a promising first step toward the growth of thin CsI layers on high aspect ratio, highly-dense micropost assemblies fabricated from Si templates