Field emission triode amplifier utilizing aligned carbon nanotubes

摘要

A vacuum field emission transistor utilizing aligned carbon nanotubes (CNTs) to form a triode configured as a common emitter amplifier is investigated. DC and AC performances of this triode amplifier are reported. The vertically aligned CNT emitters for the microtriodes with a convex surface profile were selectively synthesized utilizing microwave plasma chemical vapor deposition (MPCVD) with Ni or Co as catalysts. The single-mask micro-fabrication process achieved a CNT microtriode array (array size: 34 x 84, element dimension: 10 mu m X 10 mu m square, element spacing: 20 mu m) with self-aligned gate. Transistor curves for the CNT triode with anode current (I_a) as a function of anode voltage (V_a) for different gate voltages (V_g) was measured, followed by AC characterization. The triode amplifier demonstrated gate-controlled modulation of the emission current with distinct cutoff, linear and saturation regions of operation. A large DC gain or amplification factor of approx 350, transconductance of approx 2 mu S, and a computed anode resistance of 182 Mil are obtained. A large anode current of approx 3.5 mu A or current density of approx 1.2 mA/cm~2 was achieved at V_g=46 V and V_a=300 V. Saturation of the anode currents at V_a>80 V was also observed. The AC performance of the CNT triode amplifier was characterized by input voltage (v_(in)) vs. output voltage (v_(out)). The voltage gain of the triode amplifier, A_v, is given by the ratio of v_(out)/ v_(in). The estimated A_v is calculated to be approx 3.13 with a phase shift of approx 180 deg , as expected. A larger A_v could be attained if larger R_L is applied. Preliminary frequency response of the triode amplifier is presented. The results obtained thus far demonstrate that the CNT triode amplifier can be a promising amplifier candidate.