Nanotechnology Now

Our NanoNews Digest Sponsors

Heifer International

Wikipedia Affiliate Button

Home > Press > Seeing in color at the nanoscale: Berkeley Lab scientists develop a new nanotech tool to probe solar-energy conversion

A new microscopy tool promises to revolutionize nanoscale imaging. Left, a design schematic of the so-called “campanile” microscopy tip. Right, an electron micrograph of the tip and, inset, the UC Berkeley campanile bell-tower for which it is named.
A new microscopy tool promises to revolutionize nanoscale imaging. Left, a design schematic of the so-called “campanile” microscopy tip. Right, an electron micrograph of the tip and, inset, the UC Berkeley campanile bell-tower for which it is named.

Abstract:
If nanoscience were television, we'd be in the 1950s. Although scientists can make and manipulate nanoscale objects with increasingly awesome control, they are limited to black-and-white imagery for examining those objects. Information about nanoscale chemistry and interactions with light—the atomic-microscopy equivalent to color—is tantalizingly out of reach to all but the most persistent researchers.

Seeing in color at the nanoscale: Berkeley Lab scientists develop a new nanotech tool to probe solar-energy conversion

Berkeley, CA | Posted on December 13th, 2012

But that may all change with the introduction of a new microscopy tool from researchers at the Department of Energy (DOE)'s Lawrence Berkeley National Laboratory (Berkeley Lab) that delivers exquisite chemical details with a resolution once thought impossible. The team developed their tool to investigate solar-to-electric energy conversion at its most fundamental level, but their invention promises to reveal new worlds of data to researchers in all walks of nanoscience.

"We've found a way to combine the advantages of scan/probe microscopy with the advantages of optical spectroscopy," says Alex Weber-Bargioni, a scientist at the Molecular Foundry, a DOE nanoscience center at Berkeley Lab. "Now we have a means to actually look at chemical and optical processes on the nanoscale where they are happening."

Weber-Bargioni is one of the corresponding authors of a paper reporting this research, published in Science. The paper is titled, "Mapping local charge recombination heterogeneity by multidimensional nanospectroscopic imaging." Co-authoring the paper are Wei Bao, Mauro Meli, Frank Ogletree, Shaul Aloni, Jeffrey Bokor, Stephano Cabrini, Miquel Salmeron, Eli Yablonovitch, and James Schuck of Berkeley Lab; Marco Staffaroni of the University of California, Berkeley; Hyuck Choo of Caltech; and their colleagues in Italy, Niccolo Caselli, Francesco Riboli, Diederik Wiersma, and Francesca Intoni.

"If you want to characterize materials, particularly nanomaterials, the way it's traditionally been done is with electron microscopies and scan/probe microscopies because those give you really high, sub-atomic spatial resolution," says co-author James Schuck, a nano-optics researcher at the Molecular Foundry. "Unfortunately, what they don't give you is chemical, molecular-level information."

For chemical information, researchers typically turn to optical or vibrational spectroscopy. The way a material interacts with light is dictated to large part by its chemical composition, but for nanoscience the problem with doing optical spectroscopy at relevant scales is the diffraction limit, which says you can't focus light down to a spot smaller than approximately half its wavelength, due to the wave-nature of light.

To get around the diffraction limit, scientists employ "near-field" light. Unlike the light we can see, near-field light decays exponentially away from an object, making it hard to measure, but it contains very high resolution—much higher than normal, far-field light.

Says Schuck, "The real challenge to near-field optics, and one of the big achievements in this paper, is to create a device that acts as a transducer of far-field light to near-field light. We can squeeze it down and get very enhanced local fields that can interact with matter. We can then collect any photons that are scattered or emitted due to this interaction, collect in the near field with all this spatial frequency information and turn it back into propagating, far-field light."

The trick for that conversion is to use surface plasmons: collective oscillations of electrons that can interact with photons. Plasmons on two surfaces separated by a small gap can collect and amplify the optical field in the gap, making a stronger signal for scientists to measure.

Researchers have exploited these effects to make near-field probes with a variety of geometries, but the experiments typically require painstaking optical alignment, suffer from background noise, only work for narrow frequency ranges of light and are limited to very thin samples.

In this latest work, however, the Berkeley Lab researchers transcended these limitations with a cleverly designed near-field probe. Fabricated on the end of an optical fiber, the probe has a tapered, four-sided tip. The researchers named their new tool after the campanile church tower it resembles, inspired by the landmark clock tower on the UC Berkeley campus. Two of the campanile's sides are coated with gold and the two gold layers are separated by just a few nanometers at the tip. The three-dimensional taper enables the device to channel light of all wavelengths down into an enhanced field at the tip. The size of the gap determines the resolution.

In a regular atomic force microscope (AFM), a sharp metal tip is essentially dragged across a sample to generate a topological map with sub-nanoscale resolution. The results can be exquisite but only contain spatial information and nothing about the composition or chemistry of the sample.

Replacing the usual AFM tip with a campanile tip is like going from black-and-white to full color. You can still get the spatial map but now there's a wealth of optical data for every pixel on that map. From optical spectra, scientists can identify atom and molecule species, and extract details about electronic structure.

"That's the beauty of these tips," says Schuck. "You can just put them on the end of an optical fiber and then it's just like using a regular AFM. You don't have to be a super near-field jock anymore to get this type of data."

The team developed their new tool to study indium-phosphide nanowires. These nanowires, with the nearly ideal band gap of 1.4 electron-volts, are well-suited to converting solar energy to electricity. The researchers found that the nanowires were not the homogeneous objects previously thought, but instead had varying optoelectronic properties along their length, which could radically alter how sunlight is converted to electricity. They also found that photoluminescence, an indication of the relationship between light and electricity, was seven-times stronger in some parts of a nanowire than others. This is the first time anyone has measured these events on such a small scale.

Weber-Bargioni says: "Details like this about indium-phosphide nanowires are important because if you want to use these suckers for photocatalysis or a photovoltaic material then the length scale at which we're measuring is where everything happens. This information is really important to understand how, for example, the fabrication and surface treatment of nanowires influences these charge recombination velocities. These determine how efficiently a solar device can convert photons into usable electrons."

Adds Schuck: "We realized that this is really the optimal way to do any kind of optical experiment one might want to do at the nano scale. So we use it for imaging and spectroscopy but we anticipate many other uses also."

Experiments were carried out in collaboration with the groups of Diederik Wiersma and Francesca Intonti from the European Laboratory for Non-linear Spectroscopy, Italy.

This research was supported by the DOE Office of Science.

####

About Berkeley Lab
Lawrence Berkeley National Laboratory addresses the world’s most urgent scientific challenges by advancing sustainable energy, protecting human health, creating new materials, and revealing the origin and fate of the universe. Founded in 1931, Berkeley Lab’s scientific expertise has been recognized with 13 Nobel prizes. The University of California manages Berkeley Lab for the U.S. Department of Energy’s Office of Science. For more, visit www.lbl.gov.

The Molecular Foundry is one of five DOE Nanoscale Science Research Centers (NSRCs), national user facilities for interdisciplinary research at the nanoscale, supported by the DOE Office of Science. Together the NSRCs comprise a suite of complementary facilities that provide researchers with state-of-the-art capabilities to fabricate, process, characterize, and model nanoscale materials, and constitute the largest infrastructure investment of the National Nanotechnology Initiative. The NSRCs are located at DOE’s Argonne, Brookhaven, Lawrence Berkeley, Oak Ridge and Sandia and Los Alamos national laboratories. For more information about the DOE NSRCs, please visit http://science.energy.gov/bes/suf/user-facilities/nanoscale-science-research-centers/.

DOE’s Office of Science is the single largest supporter of basic research in the physical sciences in the United States, and is working to address some of the most pressing challenges of our time. For more information, please visit the Office of Science website at science.energy.gov/.

For more information, please click here

Contacts:
Alison Hatt
510-495-2391

Copyright © Berkeley Lab

If you have a comment, please Contact us.

Issuers of news releases, not 7th Wave, Inc. or Nanotechnology Now, are solely responsible for the accuracy of the content.

Bookmark:
Delicious Digg Newsvine Google Yahoo Reddit Magnoliacom Furl Facebook

Related Links

For more information about the Molecular Foundry go here:

For more information about the research of Jim Schuck go here:

Related News Press

News and information

Oxford Instruments announces Dr Kate Ross as winner of the 2018 Lee Osheroff Richardson Science Prize for North and South America February 20th, 2018

Computers aid discovery of new, inexpensive material to make LEDs with high color quality February 20th, 2018

Unconventional superconductor may be used to create quantum computers of the future: They have probably succeeded in creating a topological superconductor February 19th, 2018

Photonic chip guides single photons, even when there are bends in the road February 16th, 2018

Imaging

Graphene on toast, anyone? Rice University scientists create patterned graphene onto food, paper, cloth, cardboard February 13th, 2018

New method enables high-resolution measurements of magnetism February 7th, 2018

Leti Presents Optical-Equipment Curving Technology that Improves Performance, Cuts Costs: ‘Disruptive Approach’ for Imaging Applications Presented in Paper At Photonics West and Demonstrated in Leti’s Booth February 2nd, 2018

Chemistry

Ultra-efficient removal of carbon monoxide using gold nanoparticles on a molecular support: New method and mechanism for state-of-the-art gas purification February 9th, 2018

Fast-spinning spheres show nanoscale systems' secrets: Rice University lab demonstrates energetic properties of colloids in spinning magnetic field February 7th, 2018

Laboratories

Atomic Flaws Create Surprising, High-Efficiency UV LED Materials: Subtle surface defects increase UV light emission in greener, more cost-effective LED and catalyst materials February 8th, 2018

Govt.-Legislation/Regulation/Funding/Policy

Computers aid discovery of new, inexpensive material to make LEDs with high color quality February 20th, 2018

Arrowhead Receives Regulatory Clearance to Begin Phase 1/2 Study of ARO-HBV for Treatment of Hepatitis B February 15th, 2018

Arrowhead Pharmaceuticals Receives Orphan Drug Designation for ARO-AAT February 15th, 2018

Rutgers-Led Innovation Could Spur Faster, Cheaper, Nano-Based Manufacturing: Scalable and cost-effective manufacturing of thin film devices February 14th, 2018

Discoveries

Computers aid discovery of new, inexpensive material to make LEDs with high color quality February 20th, 2018

Unconventional superconductor may be used to create quantum computers of the future: They have probably succeeded in creating a topological superconductor February 19th, 2018

Photonic chip guides single photons, even when there are bends in the road February 16th, 2018

'Living bandages': NUST MISIS scientists develop biocompatible anti-burn nanofibers February 15th, 2018

Announcements

Oxford Instruments announces Dr Kate Ross as winner of the 2018 Lee Osheroff Richardson Science Prize for North and South America February 20th, 2018

Computers aid discovery of new, inexpensive material to make LEDs with high color quality February 20th, 2018

Unconventional superconductor may be used to create quantum computers of the future: They have probably succeeded in creating a topological superconductor February 19th, 2018

Photonic chip guides single photons, even when there are bends in the road February 16th, 2018

Tools

Oxford Instruments announces Dr Kate Ross as winner of the 2018 Lee Osheroff Richardson Science Prize for North and South America February 20th, 2018

New method enables high-resolution measurements of magnetism February 7th, 2018

Nanometrics Selected for Fab-Wide Process Control Metrology by Domestic China 3D-NAND Manufacturer: Latest Fab Win Includes Comprehensive Suite for Substrate, Thin Film and Critical Dimension Metrology February 7th, 2018

A new radiation detector made from graphene: A new bolometer exploits the thermoelectric properties of graphene February 6th, 2018

Energy

Round-the-clock power from smart bowties February 5th, 2018

Silk fibers could be high-tech ‘natural metamaterials’ January 31st, 2018

A simple new approach to plastic solar cells: Osaka University researchers intelligently design new highly efficient organic solar cells based on amorphous electronic materials with potential for easy printing January 28th, 2018

Nature paper by Schlumberger researchers used photothermal based nanoscale IR spectroscopy to analyze heterogeneous process of petroleum generation January 23rd, 2018

Solar/Photovoltaic

A simple new approach to plastic solar cells: Osaka University researchers intelligently design new highly efficient organic solar cells based on amorphous electronic materials with potential for easy printing January 28th, 2018

Tweaking quantum dots powers-up double-pane solar windows: Engineered quantum dots could bring down the cost of solar electricity January 2nd, 2018

Record high photoconductivity for new metal-organic framework material December 15th, 2017

Inorganic-organic halide perovskites for new photovoltaic technology November 6th, 2017

NanoNews-Digest
The latest news from around the world, FREE



  Premium Products
NanoNews-Custom
Only the news you want to read!
 Learn More
NanoStrategies
Full-service, expert consulting
 Learn More











ASP
Nanotechnology Now Featured Books




NNN

The Hunger Project