Nima Rouhi

Fundamental Limits on the Mobility of Nanotube‐Based Semiconducting Inks

[∗] N. Rouhi , D. Jain , K. Zand Prof. P. J. Burke Integrated Nanosytems Research Facility Department of Electrical Engineering and Computer Science University of California-Irvine Irvine, CA, USA; pburke@uci.edu Carbon-nanotube-based semiconducting inks offer great promise for a variety of applications including fl exible, transparent, and printed electronics and optics. A critical drawback of such inks has been the presence of metallic nanotubes, which causes high-mobility inks to suffer from poor on/off ratios, preventing their applications in a wide variety of commercial settings. Here, we report a comprehensive study of the relationship between mobility, density, and on/off ratios of solution-based, deposited semiconducting nanotube ink used as the channel in fi eld effect transistors. A comprehensive spectrum of the density starting from less than 10 tubes μ m − 2 to the high end of more than 100 tubes μ m − 2 have been investigated. These studies indicate a quantitative trend of decreasing on/off ratio with increasing density and mobility, starting with mobilities over 90 cm 2 V − 1 s − 1 (approaching that of p-type Si MOSFETs) but with on/off ratios ∼ 10, and ending with on/off ratios > 10 5

Nanoscale Devices for Large-Scale Applications

In this article, the authors review the progress toward carbon nanotube based electronics and consider the implications for application of nanotubes in analogue RF devices and RF system applications as well as recent prospects in printed electronics, especially printed RFID tags. The author also points out that nanowire devices are also starting to show similar performance in the RF domain, with similar manufacturing challenges.

Broadband conductivity of graphene from DC to THz

In this paper for the first time we have studied the broadband sheet conductance of few-layer graphene on single-crystal quartz substrate. Few-layer graphene was grown on Nickel coated Si wafers and transferred to the target substrate, which is single crystal quartz. High frequency measurements at X-band (8–12 GHz), using WR90 waveguide were performed. In addition, sheet resistance at W-band (75–100 GHz) and 1 THz range is also measured providing a comprehensive frequency sheet conductance calculation. The sheet resistance is extracted form the transmission coefficient (S21). The results present small variation at different frequency bands, and are quite stable within the bands.

Effect of source, surfactant, and deposition process on electronic properties of nanotube arrays

The electronic properties of arrays of carbon nanotubes from several different sources differing in the manufacturing process used with a variety of average properties such as length, diameter, and chirality are studied. We used several common surfactants to disperse each of these nanotubes and then deposited them on Si wafers from their aqueous solutions using dielectrophoresis. Transport measurements were performed to compare and determine the effect of different surfactants, deposition processes, and synthesis processes on nanotubes synthesized using CVD, CoMoCAT, laser ablation, and HiPCO.

All-semiconducting nanotube devices for RF and microwave applications

Purified, all-semiconducting nanotubes offer great promise for a variety of applications in RF and microwave electronics. In this work, we present device performance of thin-film transistors fabricated using a spin-coating method that is economical and lends itself to mass manufacturing of nanotube electronics.

An RF Circuit Model of a Quantum Point Contact

We develop a realistic, physics based, practical RF circuit model for the AC impedance of a quantum point contact that includes the ohmic contacts, the on-chip ¿lead¿ resistance and kinetic inductance, and the quantum point contact impedance itself. The kinetic inductance of the electrons in the ¿leads¿ in series with the quantum point contact capacitance form a resonant tank circuit whose resonant frequency depends on the width of the quantum point contact channel. These measurements probe devices in the following qualitative regime: they are in the ballistic limit, and the measurement frequency is higher than the electron scattering frequency.

Novel approach towards performance enhancement of all semiconducting carbon nanotube devices for printed electronics

Carbon nanotube based semiconducting inks are now being widely used by researchers for several exotic applications including but not limited to flexible TFTs, biosensors and printed electronics. As this point it is crucial to be able to have a precise control over the electronic performance of such devices. In this work, we present our progress towards thin film transistor fabrication where 99% semiconducting nanotubes ink is used as the starting material. By controlling the density of nanotubes in the network, we laid down a road map to predict and enhance the device performance based on their mobility and on/off ratio. From this work the DC analysis of devices characterization shows a mobility more than 90 cm2/V-s and also on/off ratios as high as, 105 have been achieved.

Carbon nanotube purified ink-based printed thin film transistors: Novel approach in controlling the electrical performance

In this paper we present a comprehensive study of the solution-based printed carbon nanotube purified-ink devices while introducing a new idea of controlling the electronic performance of these devices. One of the most important concerns in nanoelectronics is whether the nanotube-based devices will ever enter the reality world of circuit designs? What are the fundamental and critical issues to be resolved? Which parameters affect the device performance most? A comprehensive study of the relationship between mobility, on/off ratio, and nanotube network density is presented for the first time in detail. This study reveals a clear road map towards experimental control over the performance of solution-based nanotube thin film transistors for a wide range of state-of-the-art applications.

Semiconducting-enriched printed carbon nanotube mat used for fabrication of thin film transistors

Semiconducting nanotubes, theoretically, offer great promise for a variety of applications in RF and microwave electronics. In this work, we present device performance of thin-film transistors fabricated using a spin-coating purified all-semiconducting nanotubes that is economical and lends itself to mass manufacturing of nanotube electronics.