Chapter 10. Measurement of active nanoelectronic devices
Thomas M. Wallis, Pavel Kabos
Many of the most promising applications of nanomaterials involve active, nanoelectronic devices. For example, the intrinsic transport properties of single-walled, carbon nanotubes (CNTs) enable field effect transistors (FETs) that allow higher current densities and lower distortion than their conventional counterparts. In addition, CNTFETs offer the tantalizing possibility of field effect transistors (FETs) with cutoff frequencies in the terahertz range, at least in theory. Given that a typical, 100 nm-long CNT has a capacitance on the order of C = 4 aF and a quantized resistance as small as R = 6.25 kΩ, a rough calculation of the RC time constant of such a nanotube is on the order of 160 fs, corresponding to a frequency of about 6 THz. Early measurements of the transconductance in CNT transistors also suggested potential cutoff frequencies well into the terahertz regime. However, in practice, the extrinsic cutoff frequencies of realizable CNTFETs have been on the order of tens of gigahertz. The realization of CNTFETs with terahertz-scale, extrinsic cutoff frequencies faces significant, potentially insurmountable challenges. For instance, materials-science challenges include the isolation of large numbers of uniform, semiconducting CNTs. Also, while the intrinsic properties of CNTs favor high cutoff frequencies, optimization of the extrinsic cutoff frequency requires minimization of contact reactance and other parasitics. These fabrication challenges are also intimately tied to the need for impedance matching. Moreover, quantum mechanical effects such as kinetic inductance and quantum capacitance can play significant roles in device performance, depending upon the intended application and desired operating frequency. Ultimately, the cutoff frequencies of CNTFETs appear unlikely to surpass those of less expensive, conventional FETs. However, the unique properties of CNTs may yet be leveraged for specialized applications such as high-linea
Measurement Techniques for Radio Frequency Nanoelectronics
and Kabos, P.
Chapter 10. Measurement of active nanoelectronic devices, Cambridge University Press, Cambridge, -1, [online], https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=922181
(Accessed June 3, 2023)