Recently developed processes have enabled bottom-up chemical synthesis of graphene nanoribbons (GNRs) with precise atomic structure. These GNRs are ideal candidates for electronic devices because of their uniformity, extremely narrow width below 1 nm, atomically perfect edge structure, and desirable electronic properties. Here, we demonstrate nano-scale chemically synthesized GNR field-effect transistors, made possible by development of a reliable layer transfer process. We observe strong environmental sensitivity and unique transport behavior characteristic of sub-1 nm width GNRs.

We develop short-channel transistors using solutionprocessed single-walled carbon nanotubes (SWNTs) to evaluate the feasibility of those SWNTs for high-performance applications. Our results show that even though the intrinsic field-effect mobility is lower than the mobility of CVD nanotubes, the electrical contact between the nanotube and metal electrodes is not significantly affected. It is this contact resistance which often limits the performance of ultrascaled transistors. Moreover, we found that the contact resistance is lowered by the introduction of oxygen treatment. Therefore, high-performance solution-processed nanotube transistors with a 15 nm channel length were obtained by combining a top-gate structure and gate insulators made of a high-dielectric-constant ZrO 2 film. The combination of these elements yields a performance comparable to that obtained with CVD nanotube transistors, which indicates the potential for using solution-processed SWNTs for future aggressively scaled transistor technology.

Carbon nanotube networks in thin-film type transistors were studied experimentally, comparing the use of pre-separated semiconducting enriched nanotubes (90% and 99% purity) to examine how topology affects the properties of the devices. Measurements are reported for two deposition methods used for network formation: random and spin-aligned deposition methods. The results show that the thin-film transistors fabricated via spin-aligned deposition demonstrate better electrical uniformity and performance than those produced by the random network deposition method. Our results imply that coverage and alignment are strongly correlated with the properties of the devices and should therefore be simultaneously optimized for improved electrical uniformity and performance.Networks of single-walled carbon nanotubes (SWNTs) represent a class of electronic materials that can serve as high-performance channel layers in thin-film field effect transistors (TFTs) and other devices. 1-5 The favorable properties of such films may provide a route to practical nanotube-based electronic systems by eliminating the need for precise control over the properties or positions of individual SWNTs. Although single-tube devices can potentially achieve the intrinsic mobility of a semiconducting SWNT, 6 single-tube assembly methods are extremely challenging to scale up and are not yet technologically practical for largearea applications. Therefore, thin films of SWNTs consisting of either random or well-aligned networks represent a promising path to scalable device manufacturing. 7,8 However, such films may have a lower mobility than single-tube devices because tube-tube crossings limit the current flow from source to drain when the channel length is greater than the nanotube length. 9,10 Increasing the network density can increase the current but can also lead to a shorted TFTs 11 resulting from a detrimental increase in the probability of having a percolation path dominated by metallic species.The problem of the co-existence of metallic and semiconducting SWNTs can be addressed by using pre-purified semiconducting enriched SWNTs produced, for example, by density gradient ultracentrifugation. 12 However, limitations are also imposed in this process because cost-effective, 100% pure semiconducting nanotubes are not available. Therefore, all commercially available enriched solutions contain some amount of metallic nanotubes, which may negatively impact semiconducting device properties. To date, there has been progressive research based on highly preenriched semiconducting nanotubes (i.e., over 95% semiconducting nanotubes). 13,14 Nevertheless, many interesting issues remain to be studied. Open questions include whether improved performance can be achieved with separated nanotubes of lower enrichment (<95%) and how does network topology affect the transport and uniformity properties. 15 Here, we present the results of experimental studies designed to address these questions by evaluating the transport and uniformity properties of transistors fabric...

Transistors utilizing carbon nanotube (CNT) thin films have exhibited high on-currents and mobilites greater than those of alternative channel materials. One critical problem that has limited the utilization of CNT thin-film transistors (TFTs) is the occurrence of unavoidable parasitic current paths stemming from metallic nanotubes. In this work, we experimentally demonstrate high-yield, high-performance TFTs composed of a highly purified single-walled carbon nanotube (SWNT) network. A solution process for a highly separated 99.9% semiconducting SWNT solution is used to acquire a significant enhancement in transistor performance, such as a high on/off ratio, high mobility, and high yields close to 100%.

Energy efficient nanomagnetic logic (NML) computing architectures propagate binary information by relying on dipolar field coupling to reorient closely spaced nanoscale magnets. Signal propagation in nanomagnet chains has been previously characterized by static magnetic imaging experiments; however, the mechanisms that determine the final state and their reproducibility over millions of cycles in high-speed operation have yet to be experimentally investigated. Here we present a study of NML operation in a high-speed regime. We perform direct imaging of digital signal propagation in permalloy nanomagnet chains with varying degrees of shape-engineered biaxial anisotropy using full-field magnetic X-ray transmission microscopy and time-resolved photoemission electron microscopy after applying nanosecond magnetic field pulses. An intrinsic switching time of 100 ps per magnet is observed. These experiments, and accompanying macrospin and micromagnetic simulations, reveal the underlying physics of NML architectures repetitively operated on nanosecond timescales and identify relevant engineering parameters to optimize performance and reliability.

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