Wireless Nanotechnology Report

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Introduction
This report introduces the application of carbon nanotubes (CNTs) and nanotechnology to the wireless realm. Use of carbon nanotubes in high-frequency electronic devices has several advantages. Specifically, such components result in favorable characteristics, such as high transconductance and long mean-free paths.1 Transconductance is the ratio of a change in output current to the change in input voltage that caused it. A high transconductance means a more efficient production of charge carriers. Mean-free path is the mean distance traveled by charge carriers before a scattering-based collision. A long mean-free path results in more efficient charge carrier transport



Description of the Process
CNT applications as an RF mixer (which convert RF power at one frequency into power at another frequency to assist in the simplification of digital signal processing) have been demonstrated by multiple groups. Kocabas et al. have “fabricated nanotube transistor radios, in which SWNT devices provide all key functions, including resonant antennas, fixed RF amplifiers, RF mixers, and audio amplifiers.”8 Rosenblatt et al. “have probed the electrical properties of top-gated single-walled carbon nanotube transistors at frequencies up to 50 GHz by using the device as a microwave mixer.”9 All of these groups use the CNT’s nonlinearity of the drain current with respect to the gate source current. Another group, Rodriguez et al., used a slightly different technique, taking advantage of the nonlinearity of the source-drain current relationship created by the zero-bias anomaly that manifests at low temperatures, in the case of this group, at T = 77 K.



Wireless Nanotechnology Report Written by Ryan Goldstein

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As demonstrated in Figure 5 (a), the demodulated signal is very close to the absolute value of the numerical second derivative of the current-voltage trace. A direct relationship between the applied RF power and the detected output signal is essentially linear, indicating that Iresolved is proportional to VRF2, supported by the plot in . Challenges and Opportunities
One significant difference between various methods of utilizing CNTs to demodulate amplitude modulated signals is two-terminal vs. three-terminal nonlinear devices. The sole advantage with a three-terminal device is that it can be optimized in terms of signal amplification (i.e. one additional variable to adjust). The fact that two-terminal devices cannot be optimized in this way is a fundamental property of such devices. However, two-terminal devices are much simpler and easier to work with and analyze. Rutherglen et al.’s development of such a two-terminal device represents the first physical demonstration, originally proposed by Manohara et al. in 2005.17