Since their discovery, carbon nanotubes have fascinated many researchers due to their unprecedented properties. However, a major drawback in utilizing carbon nanotubes for practical applications is the difficulty in positioning or growing them at specific locations. Here we present a simple, rapid, non-invasive and scalable technique that enables optical imaging of carbon nanotubes. The carbon nanotube scaffold serves as a seed for nucleation and growth of small size, optically visible nanocrystals. After imaging the molecules can be removed completely, leaving the surface intact, and thus the carbon nanotube electrical and mechanical properties are preserved. The successful and robust optical imaging allowed us to develop a dedicated image processing algorithm through which we are able to demonstrate a fully automated circuit design resulting in field effect transistors and inverters. Moreover, we demonstrate that this imaging method allows not only to locate carbon nanotubes but also, as in the case of suspended ones, to study their dynamic mechanical motion.

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Bi-stable mechanical resonators play a significant role in various applications, such as sensors, memory elements, quantum computing and mechanical parametric amplification. While carbon nanotube based resonators have been widely investigated as promising NEMS devices, a bi-stable carbon nanotube resonator has never been demonstrated. Here, we report a class of carbon nanotube resonators in which the nanotube is buckled upward. We show that a small upward buckling yields record electrical frequency tunability, whereas larger buckling can achieve Euler-Bernoulli bi-stability, the smallest mechanical resonator with two stable configurations to date. We believe that these recently-discovered carbon nanotube devices will open new avenues for realizing nano-sensors, mechanical memory elements and mechanical parametric amplifiers. Furthermore, we present a three-dimensional theoretical analysis revealing significant nonlinear coupling between the in-plane and out-of-plane static and dynamic modes of motion, and a unique three-dimensional Euler-Bernoulli snap-through transition. We utilize this coupling to provide a conclusive explanation for the low quality factor in carbon nanotube resonators at room temperature, key in understanding dissipation mechanisms at the nano scale.

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.