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Enhancement of the Electron Spin Resonance of Single-Walled Carbon Nanotubes by Oxygen Removal
Rice, William D.,Weber, Ralph T.,Leonard, Ashley D.,Tour, James M.,Nikolaev, Pavel,Arepalli, Sivaram,Berka, Vladimir,Tsai, Ah-Lim,Kono, Junichiro American Chemical Society 2012 ACS NANO Vol.6 No.3
<P>We have observed a nearly 4-fold increase in the electron spin resonance (ESR) signal from an ensemble of single-walled carbon nanotubes (SWCNTs) due to oxygen desorption. By performing temperature-dependent ESR spectroscopy both before and after thermal annealing, we found that the ESR in SWCNTs can be reversibly altered <I>via</I> the molecular oxygen content in the samples. Independent of the presence of adsorbed oxygen, a Curie law (spin susceptibility ∝ 1/<I>T</I>) is seen from ∼4 to 300 K, indicating that the probed spins are finite-level species. For both the pre-annealed and post-annealed sample conditions, the ESR line width decreased as the temperature was increased, a phenomenon we identify as motional narrowing. From the temperature dependence of the line width, we extracted an estimate of the intertube hopping energy; for both sample conditions, we found this hopping energy to be ∼1.2 meV. Since the spin hopping energy changes only slightly when oxygen is desorbed, we conclude that only the spin susceptibility, not spin transport, is affected by the presence of physisorbed molecular oxygen in SWCNT ensembles. Surprisingly, no line width change is observed when the amount of oxygen in the SWCNT sample is altered, contrary to other carbonaceous systems and certain 1D conducting polymers. We hypothesize that physisorbed molecular oxygen acts as an acceptor (p-type), compensating the donor-like (n-type) defects that are responsible for the ESR signal in bulk SWCNTs.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/ancac3/2012/ancac3.2012.6.issue-3/nn204094s/production/images/medium/nn-2011-04094s_0009.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/nn204094s'>ACS Electronic Supporting Info</A></P>
CHARGE TRANSPORT THROUGH CARBON NANOTUBE OR FULLERENE–MOLECULE–SILICON JUNCTIONS
FU-REN F. FAN,BO CHEN,AUSTEN K. FLATT,JAMES M. TOUR,ALLEN J. BARD 성균관대학교(자연과학캠퍼스) 성균나노과학기술원 2007 NANO Vol.2 No.5
We report here the current–voltage (i–V) characteristics of several (n++-Si/MNOPE/C60/Pt-tip) or (n++-Si/MNOPE/SWCNT/Pt-tip) junctions, where MNOPE = 2'-mononitro-4, 4'-bis(phenylethynyl)-1-phenylenediazonium and SWCNT = single wall carbon nanotube. A layer of C60 or SWCNT-derivatized MNOPE has strong effect on the i–V behavior of the junctions, including rectification, negative differential resistance (NDR) and switching behaviors. The i–V curve of a grafted molecular monolayer (GMM) of MNOPE atop n++-Si shows NDR behavior, whereas those of C60- and SWCNT-derivatized GMMs of MNOPE on n++-Si show strong rectifying behavior with opposite rectification polarities. With C60, larger currents were found with negative tip bias, while with SWCNT, the forward top bias was positive. Because C60 tends to be a good electron acceptor and SWCNTs tend to be good electron donors, they show different i–V behavior, as observed. Some of the (n++-Si/MNOPE/SWCNT/Pt-tip) junctions also show reversible bistable switching behavior.
Kwon, Soonbang,Kim, Tae-Wook,Jang, Seonghoon,Lee, Jae-Hwang,Kim, Nam Dong,Ji, Yongsung,Lee, Chul-Ho,Tour, James M.,Wang, Gunuk American Chemical Society 2017 ACS APPLIED MATERIALS & INTERFACES Vol.9 No.39
<P>A memristor architecture based on metal-oxide materials would have great promise in achieving exceptional energy efficiency and higher scalability in next-generation electronic memory systems. Here, we propose a facile method-for fabricating selector-less memristor arrays using an engineered nanoporous Ta2O5-x architecture. The device was fabricated in the form of crossbar arrays, and it functions as a switchable rectifier with a self-embedded nonlinear switching behavior and ultralow power consumption (similar to 2.7 X 10(-6) W), which results in effective suppression of crosstalk interference. In addition, we determined that the essential switching elements, such as the programming power, the sneak current, the nonlinearity value, and the device-to-device uniformity, could be enhanced by in-depth structural engineering of the pores in the Ta2O5-x layer. Our results, oil the basis of the structural .engineering of metal-oxide materials, could provide an attractive approach for fabricating simple and cost-efficient memristor. arrays with acceptable device, uniformity and low power consumption without the need for additional addressing selectors.</P>
Flexible Nanoporous WO<sub>3–<i>x</i></sub> Nonvolatile Memory Device
Ji, Yongsung,Yang, Yang,Lee, Seoung-Ki,Ruan, Gedeng,Kim, Tae-Wook,Fei, Huilong,Lee, Seung-Hoon,Kim, Dong-Yu,Yoon, Jongwon,Tour, James M. American Chemical Society 2016 ACS NANO Vol.10 No.8
<P>Flexible resistive random access memory (RRAM) devices have attracted great interest for future nonvolatile memories. However, making active layer films at high temperature can be a hindrance to RRAM device fabrication on flexible substrates. Here, we introduced a flexible nanoporous (NP) WO3-x RRAM device using anodic treatment in a room-temperature process. The flexible NP WO3-x RRAM device showed bipolar switching characteristics and a high I-ON/IOFF ratio of similar to 10(5). The device also showed stable retention time over 5 X 10(5) s, outstanding cell-to-cell uniformity, and bending endurance over 10(3) cycles when maximum bending conditions.</P>