Single Carbon Nanotube Transistor at GHz Frequency

Abstract

We report on microwave operation of top-gated single carbon nanotube transistors. From transmission measurements in the 0.1−1.6 GHz range, we deduce device transconductance g_m and gate−nanotube capacitance C_g of micro- and nanometric devices. A large and frequency-independent g_m ∼ 20 μS is observed on short devices, which meets the best dc results. The capacitance per unit gate length of 60 aF/μm is typical of top gates on a conventional oxide with ε ∼ 10. This value is a factor of 3−5 below the nanotube quantum capacitance which, according to recent simulations, favors high transit frequencies f_T = g_m/2πC_g. For our smallest devices, we find a large f_T ∼ 50 GHz with no evidence of saturation in length dependence.