A computer image of the Laboratory for Integrated Science and Engineering (LISE) that will house shared facilities for Harvard's Center for Imaging and Mesoscale Structures and NSEC, and will provide space for interdisciplinary research. LISE will contain an Imaging Laboratory for electron, scanning probe and optical microscopy, a cleanroom for nanofabrication and soft lithography, and an Advanced Materials Science Laboratory.

National Nanotechnology Infrastructure Network
Harvard University and UC Santa Barbara

Harvard and UC Santa Barbara are two of an integrated partnership of thirteen user facilities, led by Cornell and Stanford, that provide opportunities for nanoscience and nanotechnology research. At Harvard, the NNIN provides expertise in soft lithography and assembly, and computation through the Center for Imaging and Mesoscale Structures. At UCSB, the NNIN provides expertise in optics and electronic materials. The NNIN was funded by the NSF in January 2004.

Cablecasting Nanotech News via New England Cable News
C.L. Alpert and D. Davis

… reaching as many as 2.8 million homes and businesses

a) How to make a nanobattery.

b) How Xiaowei Zhuang videotaped individual influenza viruses.

c) How iron nanoparticles might be used to clean up toxic waste sites.

d) Modeling Eric Mazur and Limin Tong's method for making glass nanofibers.

Each Thursday morning, New England Cable News anchors visit the Current Science & Technology Center at the Museum of Science via robotic cameras linked by fiber optics to their Needham, MA studio. Once a month, NSEC Education Associate Joel Rosenberg delivers lively three-minute presentations and demonstrations about nanotech research. The cablecasts are repeated throughout the day and archived at . This live cablecasting partnership was developed under the direction of NSEC Senior Investigator for Educational Outreach Carol Lynn Alpert, and is the first of its kind in the nation.

Imaging Electron Flow
M. Topinka, R.M. Westervelt, and E.J. Heller

Cover of Physics Today, Dec. 2003 — Simulation of the flow of electron waves by E.J. Heller.

This issue contains a review of imaging electron flow in two-dimensional electron gases by Topinka, Heller and Westervelt including their collaborative research.

Electron Resonator Simulations
E.J. Heller and R.M. Westervelt

Waves injected into two resonators in a two-degree of freedom electron gas (2DEG) emerge through openings in the cavities. This image illustrates the new capability we have developed for rapid testing of barrier gate structures, by running wave packets inside scanned or hand drawn images of the devices.

Thermal Electron Wave Packets
E.J. Heller and R.M. Westervelt

A thermal wave packet (whose energy distribution is derived from its temperature) is shown emerging from a small opening (a quantum point contact, or QPC) from which is spreads out, hitting impurities. These scatter the waves, some of which head back to the QPC. They can interfere there to produce interference fringes in an image of electron flow only if they arrive at the same time.

Interference of Thermal Electron Wavepackets
E.J. Heller and R.M. Westervelt

A thermal wavepacket has been sent from below, spreading out and bouncing against the two mirrors shown in the right and left portions of the image. After one bounce from the farther mirror, and two from the closer one, parts of the wavepacket are arriving at the same time back at the QPC. By moving the mirror slightly (about 1/4 of a deBroglie wavelength) the resulting interference from the two paths goes from destructive (left, less flux seen going down) to constructive (right, more flux going down).

Micropost Matrix
T.Hunt, D. Ham, and R.M. Westervelt

Micropost matrix for trapping and manipulating single cells.
(a) Micrograph of the micropost matrix.
(b) A schematic 3-D view of the device.
We have developed a micropost matrix that can move small particles and biological cells, through a microfluidic system using dielectrophoresis. Rf voltages are separately applied to each post, under computer control. The micropost matrix can independently trap and move a number of particles or cells through the fluid.

Pumping and Focusing Pure Spin
C.M. Marcus, B.I. Halperin

With growing interest in the spin of electrons comes the need for a spin battery, analogous to a conventional (charge) battery for creating voltages in a circuit. We have used quantum coherence to produce a pump that can independently pump spins of different orientation (with respect to an externally applied magnetic field). When the two independent currents — one for spin-up and one for spin-down — exactly cancel, then no charge is pumped. However, this condition means that a spin-down current is moving to the left, say, and an equal spin-up current to the right. We have realized such a "pure" spin pump. What’s more, we have taken the spin current and made it bend around a loop, focus it, and inject it into a narrow gap.

The figure shows in the top frame total pumped current using a mesoscopic quantum pump. The bottom frame shows spin sensitive (green) and spin insensitive (black) current detection (bottom frame, black) measured at the same time as the current measured in the top frame. At zeros of total current, the spin dependent current is nonzero. At these points a pure spin current is being pumped. Top inset shows a schematic of the cyclic pumping cycle needed to make a charge or spin pump. The bottom inset shows the measurement set-up where a pumped dot is embedded in a focusing geometry. The quantum point contact on the collector can be made spin sensitive (in an external field) by adjusting the gate voltage to have partial transmission.

Kondo Effect in a Single Electron Transistor Excited by Microwaves
M.A. Kastner, C.M. Marcus

(A) Evolution of the Kondo peak with increasing microwave voltage Vdsosc applied to a single electron transistor SET at T = 100 mK.
(B) Separation between the satellites and the central peak as a function of the microwave voltage. The horizontal line is hf/e where h is Planck’s constant and f is the microwave frequency

Growth of Single-Crystal VO2 Nanowires
H. Park and B.I. Halperin

(a) High resolution TEM image of a representative VO2 nanowire, illustrating lattice fringes.
(b) Diagram of a nanowire with the growth surfaces indicated.
Synthesis of single-crystal VO2 nanowires was achieved using a simple vapor transport method in a tube furnace. VO2 is an attractive material for a Mott field effect transistor, where the channel undergoes an electrically driven Mott metal-insulator transition.

Metal-semiconductor Nano-composite Material as seen in Cross-section in an Electron Microscope Image
D. Klenov, D. Driscoll, M. Hanson, S. Stemmer and A.C. Gossard

Dark-colored lines are layers of metal islands (erbium arsenide) in a semiconductor (indium gallium arsenide). The unique honeycomb structure occurs with alternate growth of ErAs and InGaAs by molecular beam epitaxy. The metal islands form in a spontaneous island mode of crystal growth. Faceting of the surface and appearance of the honeycomb structure occur only for metal depositions and indium content greater than a certain level.

Improved Room Temperature Metallic Spin Valves
S.O. Valenzuela, M. Tinkham, and E. Demler

Spintronics devices, which simultaneously exploit the spin and charge of the electron, are being explored due to promising new electronic applications. Our devices consist of an aluminum wire contacted with two different ferromagnets (FM) with different coercive fields, as shown in the SEM image. Tunnel barriers between the FMs and the Al are grown in situ using a stencil mask and angle evaporation techniques. The Al is 100 nm wide while the FMs are 50nm wide and 150 nm apart, dimensions well below the spin relaxation length of ~300 nm. The measurements show the spin-valve effect at room temperature for positive and negative H-field sweep direction, with ~100 times larger signal than in previous work.

Raman Spectroscopy of Individual Carbon Nanotubes Under Strain
S.B. Cronin, M. Tinkham, and E. Demler

Raman spectroscopy of individual semiconducting carbon nanotubes is used for the first time to measure vibrational frequencies vs. strain. The strain is induced by bending the nanotubes with an AFM tip while the ends of the nanotubes are held fixed by metal electrodes, thus converting the transverse displacement to an elongation. Under strain of 1–2%, we observe the vibrational frequency to decrease by up to 40cm^–1. The Raman peaks shift back toward their original positions over a time period of order one week, implying strain relaxation over a similar period.