Self aligned hysteresis free carbon nanotube field-effect transistors

Abstract

Hysteresis phenomenon in the transfer characteristics of carbon nanotube field effect transistor (CNT FET) is being considered as the main obstacle for successful realization of electronic devices based on CNTs. In this study, we prepare four kinds of CNTFETs and explore their hysteretic behavior. Two kinds of devices comprise on-surface CNTs (type I) and suspended CNTs (type II) with thin insulating layer underneath and a single global gate which modulates the CNT conductance. The third and fourth types (types III and IV) consist of suspended CNT over a metallic local gate underneath, where for type IV the local gate was patterned self aligned with the source and drain electrodes. The first two types of devices, i.e., type I and II, exhibit substantial hysteresis which increases with scanning range and sweeping time. Under high vacuum conditions and moderate electric fields (|E|>4×106 V/cm), the hysteresis for on-surface devices cannot be eliminated, as opposed to suspended devices. Interestingly, type IV devices exhibit no hysteresis at all at ambient conditions, and from the different roles which the global and local gates play for the four types of devices, we could learn about the hysteresis mechanism of this system. We believe that these self aligned hysteresis free FETs will enable the realization of different electronic devices and sensors based on CNTs.

DC Signature of Snap-through Bistability in Carbon Nanotube Mechanical Resonators

“…■ METHODS Device Fabrication. All CNT resonators were fabricated according to the local gate self-aligned technique reported in ref 35. Briefly, source and drain electrodes were patterned using standard e-beam lithography, and Cr/Pt 7/32 nm metal layers were evaporated.…”

Mode coupling bi-stability and spectral broadening in buckled carbon nanotube mechanical resonators

“…Device structure and experimental setup Figure 1a presents the geometric structure of our devices. The fabrication is based on the technique developed recently for self-aligned local-gate suspended CNT devices 21 . Briefly, CNTs are grown by chemical vapor deposition (CVD) to create a contact between the source and drain (SD) electrodes, while suspended above a local-gate electrode (Fig.…”

“…We evaporated Cr/Pt 5/ 35 nm for the source and drain (SD) electrodes, after which we etched the SiO 2 using buffer oxide etchant (BOE) to create the local-gate trench (see supplementary text for details). Then, another step of Cr/Pt 5/35 nm evaporation was performed to create the self-aligned localgate 21 . Finally, we deposited a patterned ferritin catalyst near the SD electrodes for the CNT growth.…”

Conduction properties of semiconductive multiwalled carbon nanotubes

“…5 and 7. This is due to the well known hysteretic shifting of the gate curves, which stems from impurities and defectrelated charges in the gate insulator and possibly the CNT itself [19]. The two measurements were performed at different cooling runs, whereby a shift in the position of the TG is understandable, since the hysteresis occurs at temperatures that allow ionic mobility.…”