Aligned carbon nanotubes vacuum field emission devices

Carbon nanotubes (CNTs) possess a high aspect ratio, small radius of tip curvature, superb mechanical properties, thermal and chemical stability, making them excellent field emission cathodes for vacuum microelectronic applications. This study focuses on the design, fabrication and characterization of vacuum field emission (VFE) devices, specifically on the diode, triode and integrated differential amplifier (diff-amp) electronic device configurations, utilizing CNTs synthesized by microwave plasma chemical vapor deposition in conjunction with semiconductor microfabrication methods.; A consistent and reproducible CNTs synthesis method comprising plasma pretreatment of the catalysts prior to CNT synthesis was developed to tailor the surface profile of vertically aligned CNTs. The study found that the plasma pretreatment time and the array spacing of the micropatterned CNT emitters play an important role in achieving the desired field emission characteristics of low turn-on field, high current density and emission stability.; CNT triode arrays with a well-controlled convex-shaped emitter profile, designed per simulations for optimum field emission, were fabricated and their dc and ac performance evaluated. The triodes demonstrated good transistor characteristics with distinct linear, saturation and cutoff regions of operation. The triode amplifier achieved a low gate turn-on of ∼16 V, high current density of ∼7 A/cm2, high amplification factor of >400, and gate intercepted current of <1% of the anode current. Furthermore, a RF CNT triode amplifier with a projected 50 dB gain at cutoff frequency of ∼26 MHz and 20 dB gain at 1 GHz is achievable.; Lastly, for the first time in vacuum microelectronics, a novel integrated CNT VFE diff-amp was conceptualized, developed and microfabricated by a dual-mask process. The identical pair of integrated amplifiers was well-matched in their device characteristics with low gate turn-on voltage, large dc gain, and high transconductance. An analytical model was derived to estimate the common-mode-rejection-ratio (CMRR) of the diff-amp. The model was verified to be in reasonable agreement with the experimental data. Analysis of the measured small-signal characteristics showed a CMRR of ∼640 (∼56 dB). The successful implementation of the diff-amp demonstrates a new way to achieve temperature and radiation tolerant VFE integrated microelectronics.