Bulletin of the American Physical Society
2006 APS March Meeting
Monday–Friday, March 13–17, 2006; Baltimore, MD
Session N37: Focus Session: Nanoscale Fabrication, Assembly and Semiconductor Nanowires |
Hide Abstracts |
Sponsoring Units: DMP Chair: Latha Venkataraman, Columbia University Room: Baltimore Convention Center 340 |
Wednesday, March 15, 2006 8:00AM - 8:12AM |
N37.00001: Single electron transistors without tunnel junctions tailored by local oxidation of metallic ultra thin films Vincent Bouchiat, Marc Faucher, C\'{e}cile Delacour, Thierry Fournier, Bernard Panneteir We present the fabrication and low temperature electric properties of nanoscale metallic constrictions made by local oxidation with an Atomic Force Microscope of weakly localized niobium ultra-thin (3nm) strip lines. These constrictions implements nanoscale resistors with resistance of the order of the resistance quantum. Both laterally constrained and variable thickness junctions are made with a lateral gate coupled to the interjunction electrode. Circuits following both geometries exhibits reproducible low contrast gate oscillations at 4K which phase inverts with drain source voltage. The gate modulation of the current is in strong disagreement with the orthodox theory that involves tunnelling. Transport is interpreted as single or multiple islands in series for which Coulomb blockade is induced by the highly resistive sheet resistance. [Preview Abstract] |
Wednesday, March 15, 2006 8:12AM - 8:24AM |
N37.00002: Single-Walled Carbon Nanotubes as Shadow Masks for Nanogap Junction Fabrication Etienne De Poortere, Limin Huang, Mingyuan Huang, Shalom Wind, James Hone, Stephen O'Brien, Horst Stormer We report a technique for fabricating nanometer-scale gaps in Pt wires on insulating substrates, using individual\textit{ single-walled carbon nanotubes} as shadow masks during metal deposition. 83{\%} of the devices display current-voltage dependencies characteristic of direct electron tunneling. Fits to the current-voltage data yield gap widths in the 0.8 - 2.3 nm range for these devices, dimensions that are well suited for single-molecule transport measurements. [Preview Abstract] |
Wednesday, March 15, 2006 8:24AM - 8:36AM |
N37.00003: Self-Assembly for Large Scale Fabrication of Integrated Electronic Devices Based on 1-D Nanostructures. Juntae Koh, Minbaek Lee, Jiwoon Im, Sung Myung, Seunghun Hong Recently, electronic devices based on 1-dimensional (1-D) nanostructures (e.g. carbon nanotubes (CNTs) and nanowires) have been drawing much attention as next-generation device architecture. However, the shortage of reliable nanomanufacturing methods for such circuits has hindered their practical applications. One promising nanomanufacturing method can be `surface-programmed assembly' process, where functional molecular monolayer on the substrate guides the `selective assembly' and `alignment' of nanowires and nanotubes on the substrate without relying on any external forces. Using this method, we successfully assembled and aligned carbon nanotubes and vanadium oxide nanowires on various substrates including Au, silicon oxide, Si, Al, and polymer. Furthermore, by additional microfabrication process, we demonstrated large-scale fabrication of various device structures such as junctions and top-gate transistors based on CNTs and vanadium oxide nanowires. Significantly, since this process does not require any high-temperature processing steps, it can be applied to virtually general substrates and may remove current difficulty in manufacturing of electronic devices based on 1-D nanostructures. [Preview Abstract] |
Wednesday, March 15, 2006 8:36AM - 9:12AM |
N37.00004: Integrating molecular electronics with silicon Invited Speaker: |
Wednesday, March 15, 2006 9:12AM - 9:24AM |
N37.00005: Nanoscale devices on thin films by ultra-high-resolution lithography Michael Fischbein, Marija Drndic It is possible to achieve exceptionally high resolution with lithographic techniques that use scanning and transmission electron beams by using a thin film as a substrate. With this approach, numerous structures such as nanowires, nanorings, nanogaps and quantum dots can be made with dimensions under ten nanometers and in some cases even less than one nanometer. The flexibility of this fabrication approach also allows these extremely small structures to be easily contacted by large electrodes and therefore integrated into full electronic devices that exhibit effects due to carrier confinement. Furthermore, because these devices are on thin films, they are compatible with imaging by transmission electron microscopy (TEM). Basic devices made with this approach will be introduced. Extensions to devices with more complicated geometries and those which also include non-lithographically prepared nanostructures will be discussed as well. *This work was supported by ONR (N000140410489), NSF (DMR-0449553), NSF MRSEC (DMR00-79909) and NSF-IGERT (DGE 022166). [Preview Abstract] |
Wednesday, March 15, 2006 9:24AM - 9:36AM |
N37.00006: Correlated electrostatic force microscopy and transmission electron microscopy study of nanostructures on silicon nitride membranes Zonghai Hu, Michael Fischbein, Marija Drndic Silicon nitride membrane windows allow correlated electrostatic force microscopy and transmission electron microscopy (EFM/TEM) study of electrical and structural properties of the same nanoscale electronic devices fabricated on top of them. Under EFM, nanoscale charge transport patterns are distinguished and correlated with structural details as imaged by high resolution TEM. Examples of nanostructures studied include lithographically fabricated devices and self-organized nanocrystal arrays. Implications of the results on the transport mechanisms of these nanostructures will also be discussed. This work is supported by ONR Young Investigator Award N000140410489, ACS PRF Grant 41256-G10, NSF Career Grant DMR-0449553, and NSF NSEC Grant DMR-0425780. [Preview Abstract] |
Wednesday, March 15, 2006 9:36AM - 9:48AM |
N37.00007: Local Photocurrent Mapping of Nanowire Photodetectors with Ohmic and Schottky Contacts Yi Gu, John P. Romankiewicz, Jessica L. Lensch, Teri W. Odom, Lincoln J. Lauhon Near-field scanning photocurrent microscopy (NSPM) was used to determine the mechanisms of carrier transport and collection in CdS nanowire photodetectors. NSPM employs an apertured NSOM probe as a local ($<$100 nm) illumination source to map the local photocurrent as a function of the tip position along the device, i.e., from one metal contact to the other. Striking differences between Schottky and ohmically contacted devices have been observed in maps of the local photocurrent. In the Schottky devices, the photoinduced current is localized to the reverse biased diode, whereas in ohmic devices, the peak photoresponse position shifts continuously with applied bias. Modeling of the photocurrent profiles in ohmically contact devices gives the mobility-lifetime product for electrons and for holes. When independent carrier lifetime measurements are considered, one can extract electron and hole mobilities. As expected for CdS, the electron mobility exceeds the hole mobility, producing the observed shift of the photocurrent peak towards the hole collector. The effects of surface passivation and trap filling on carrier transport have also been explored. [Preview Abstract] |
Wednesday, March 15, 2006 9:48AM - 10:00AM |
N37.00008: Negative Differential Resistance in CdSe Nanorod Devices. Hugo Romero, Dong Tran, Gregory Calusine, Marija Drndic Semiconductor quantum rods are expected to exhibit interesting novel behaviors because of their well-defined shape with the long axis preferably grown along the unique c axis. They would also allow for efficient quasi-1D electrical transport. Thus, when organized into arrays of aligned quantum rods separated by insulating barriers, improved and unconventional electronic transport could be achieved compared to that of ``spherical'' nanocrystal arrays. Here, we report on the observation of interesting charging properties in electronic devices consisting of CdSe quantum rod thick films as the active components. The low bias regime of the current-voltage characteristics of such devices displays multiple negative differential resistance behavior and step-like structures at room temperature. This effect may be related to the alignment of localized trap levels in the insulating barriers with the carrier levels in the quantum rods. [Preview Abstract] |
Wednesday, March 15, 2006 10:00AM - 10:12AM |
N37.00009: Electron transport of nanoscale P-donor wires in silicon T.-C. Shen, S. J. Robinson, J. R. Tucker Three dimensional carrier transport in doped semiconductors has been extensively investigated. However, transport in low-dimensions is much less clear because of the difficulty to confine dopant distribution in a crystal. In the past few years we have created 2D embedded dopant sheets by exposing Si(100) surfaces to phosphine molecules in ultrahigh vacuum followed by growing epitaxial silicon over-layers at room temperature. Electron density in these delta layers can be as high as $\sim $1.5x10$^{14}$ cm$^{-2}$. We find that surface roughness dictates the carrier mobility and activation, even though all surfaces are atomically clean and locally ordered. Furthermore, applying STM e-beam lithography on a single-layer H-resist enables us to define P-donor wires at widths from 200 nm to 5 nm in 2-terminal device templates. The As-implanted electrodes in the device templates provide ohmic contact with P-donor wires. In this presentation we will discuss our electrical and magneto-resistance measurement of various P-donor nanostructures at cryogenic temperatures. The goal of this research is to apply 2D P-donor patterns as building blocks for nanoscale integrated circuits. [Preview Abstract] |
Wednesday, March 15, 2006 10:12AM - 10:24AM |
N37.00010: Confined Doping for Control of Transport Properties in Nanowires and Nanofilms Jianxin Zhong, G. Malcolm Stocks Doping, an essential element for manipulation of electronic transport in traditional semiconductor industry, is widely expected to play important role as well in control of transport properties in nanostructures. However, traditional theory of electronic disorder predicts that doping in one-dimensional and two-dimensional systems leads to carrier localization, limiting practical applications due to poor carrier mobility. Here, a novel concept is proposed that offers the possibility to significantly increase carrier mobility by confining the distribution of dopants within a particular region [1]. Thus, the doped nanostructure becomes a coupled system comprising a doped subsystem and a perfect crystalline subsystem. We showed that carrier mobility in such a dopped nanowire or a nanofilm exhibits counterintuitive behavior in the regime of heavy doping. In particular, the larger the dopant concentration the higher the carrier mobility; we trace this transition to the existence of quasi-mobility-edges in the nanowires and mobility edges in nanofilms. \begin{enumerate} \item J.X. Zhong and G.M. Stocks, Nano Lett., in press, (2005) \end{enumerate} [Preview Abstract] |
Wednesday, March 15, 2006 10:24AM - 10:36AM |
N37.00011: Field emission characteristics of GaN nanorods on self-implanted (111) Si H.W. Seo, X.M. Wang, Q.Y. Chen, L.W. Tu, Y.J. Tu, C.L. Hsiao, M. Chen, O. Lozano, D.H. Kim, P.V. Wadekar, Wei-Kan Chu Periodic arrays of GaN nanostructures have been fabricated by MBE growth on self-implanted (111) Si substrates. Nano-capillary condensation was found to be an effective catalytic process fostering the formation of epitaxially aligned GaN nanorods supported by a thin film matrix. Changes of Si substrate surface morphology as a result of ion bombardments prior to the thin-film deposition are responsible for the enhanced nanorod growth. The density of nanorods in relation to implanted ion dosages was studied. Field emission measurement was performed to understand the physical characteristics of functional devices based on such nanostructures. Experimental details and their implications for the future development of nanostructure and nano-device fabrications will be presented. [Preview Abstract] |
Wednesday, March 15, 2006 10:36AM - 10:48AM |
N37.00012: Conductance measurement of GaN nanorods O. Lozano, H.W. Seo, Q.Y. Chen, L.W. Tu, Y.J. Tu, C.L. Hsiao, M. Chen, D.H. Kim, P.V. Wadekar, Wei-Kan Chu GaN nanorods have been grown by molecular beam epitaxy over a thin-film GaN matrix on Si substrate. We have studied the conductance behaviors of a single nanorod and clusters nanorods. Transport measurement of internal emission of electrons from nanorod-clusters was carried out with metallic contacts over the nanostructure. Vacuum tunneling of externally emitted electrons from individual nanorod was measured using a scanning tunneling microscope-first in constant voltage mode to locate the more conductive nanorods, which was then followed by measurements at various applied voltage. Observations are made to distinguish thin film matrix from the nanorods by their efficiencies of electron emission. The characteristics of I-V curves will be reported and the applications of these nanorods to electron-emission devices will be discussed. [Preview Abstract] |
Wednesday, March 15, 2006 10:48AM - 11:00AM |
N37.00013: Structural and Electronic Properties of GaN and InN Nanowires grown using Hot-Wall CVD Elena Cimpoiasu, Eric Stern, Guosheng Cheng, Ryan Munden, Aric Sanders, Mark A. Reed We study the electron-mobility dependence on the free carrier concentration \textit{n} exhibited by hot-wall chemical-vapor deposition-grown gallium nitride (GaN) and indium nitride (InN) nanowires. The growth involves flow of ammonia over solid sources of gallium or indium and the substrate, which is covered with metal catalyst (in case of GaN) or is catalyst-free (in case of InN). The nanowires are subsequently deposited on oxidized silicon wafers and fabricated in field-effect transistors using optical lithography. In this way, more than 1000 devices were characterized at room temperature. Both types of nanowires show high carrier concentration ($10^{19}-10^{20}$ cm$^{-3}$ for GaN and $10^{20}-10^{21}$ cm$^{-3}$ for InN), with mobility decreasing with increasing free carrier concentration, consistent with ionized impurity scattering. Mobility levels range between below 1 to 100 cm$^{2}$/Vs. Estimations of the ionized impurity mobility indicate that GaN wires grow heavily compensated, and subsequent anneals in ammonia result in even higher compensation levels. We were also successful in doping GaN nanowires with magnesium, for p-type doping. Similar chemical, structural, and electronic analysis will be presented. This work was partially supported by DARPA through AFOSR, ARO, AFOSR, NASA, by the Department of Homeland Security, and by NSF. [Preview Abstract] |
Follow Us |
Engage
Become an APS Member |
My APS
Renew Membership |
Information for |
About APSThe American Physical Society (APS) is a non-profit membership organization working to advance the knowledge of physics. |
© 2024 American Physical Society
| All rights reserved | Terms of Use
| Contact Us
Headquarters
1 Physics Ellipse, College Park, MD 20740-3844
(301) 209-3200
Editorial Office
100 Motor Pkwy, Suite 110, Hauppauge, NY 11788
(631) 591-4000
Office of Public Affairs
529 14th St NW, Suite 1050, Washington, D.C. 20045-2001
(202) 662-8700