Nanodiamond lateral field emission triode

Summary form only given. In this work, we report the fabrication and field emission characteristics of a nanodiamond lateral triode. The device fabrication involved a single-mask process, where a uniform layer of nanodiamond film of grain size 5-10 nm grown by CH₄/H₂/N₂ MPECVD on a SOI substrate, was micropatterned using reactive ion etching in pure O₂ plasma, with aluminum as the etch barrier for delineating the anode, cathode and the gate. On etching the silicon layer beneath the nanodiamond, the 1 mum-thick buried-oxide layer of the SOI serves to isolate the electrodes and achieve close inter-electrode spacing. The triode device structure (see figure 1) has a single finger nanodiamond cathode acting as the emitter, with 2 nanodiamond fingers in close proximity to the emitter on either side forming the gate, and a straight-edge geometry serving as the nanodiamond anode. A gate-cathode distance as small as 2 mum was achieved by photolithography and the subsequent etch processes. Fabricated anode-cathode distances per design were set to vary between 20 mum and 1 mm, so as to have a wide range to observe the modulation effect of the gate on the triode characteristics for field emission characterization of the device. A Ti/Au metal contact layer was applied on the nanodiamond to provide good electrical contact. A lateral triode with 2 mum gate-cathode and 20 mum anode-cathode spacing was characterized for field emission in a vacuum of 10^-7 Torr. The triode achieved a very low gate turn-on voltage of ~9 V (threshold field: 4.5 V/mum) and displayed gate-controlled current modulation behavior whereby higher applied gate voltages gave rise to high emission current collected by the anode (see Figure 2). As a result, a large anode current of ~15 muA was achieved at V_g = 40 V and V_a = 105 V. The device characteristics showed cut-off, linear and onset of saturation regions. The transistor parameters - defining the performance of a triode amplifier were determined graphically from the DC characteristics curves. The transconductance g_m of the triode was estimated to be ~ 0.83 muS at V_a = 105 V, which will be improved by building a larger nanodiamond finger array for the electron emitter. At a constant I_a of 8 muA, the amplification factor mu was calculated to be ~ 10, indicating that this triode is an amplifier. The detailed dc characteristics of the nanodiamond lateral triode and further enhancements of the transistor performance will be investigated and presented. The nanodiamond lateral triode is a potential candidate for high frequency, high power amplification device applications