Tag Archives: APS

New method of Rayleigh scattering for better semiconductors

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Rayliegh scattering provides a scientific explanation first devised in the 19th century for why the sky is blue during the day and why it turns red in the evening. A March 4, 2014 news item on Nanowerk describes some research into measuring semiconductor nanowires with a new Rayleigh scattering technique,

A new twist on a very old physics technique could have a profound impact on one of the most buzzed-about aspects of nanotechnology.

Researchers at the University of Cincinnati [UC] have found that their unique method of light-matter interaction analysis appears to be a good way of helping make better semiconductor nanowires.

The March 4, 2014 University of Cincinnati news release, which originated the news item, has the researcher describing his work in further detail (Note: Links have been removed),

“Semiconductor nanowires are one of the hottest topics in the nanoscience research field in the recent decade,” says Yuda Wang, a UC doctoral student. “Due to the unique geometry compared to conventional bulk semiconductors, nanowires have already shown many advantageous properties, particularly in novel applications in such fields as nanoelectronics, nanophotonics, nanobiochemistry and nanoenergy.”

Wang will present the team’s research “Transient Rayleigh Scattering Spectroscopy Measurement of Carrier Dynamics in Zincblende and Wurtzite Indium Phosphide Nanowires” at the American Physical Society (APS) meeting to be held March 3-7 [2014] in Denver. …

Key to this research is UC’s new method of Rayleigh scattering, a phenomenon first described in 1871 and the scientific explanation for why the sky is blue in the daytime and turns red at sunset. The researchers’ Rayleigh scattering technique probes the band structures and electron-hole dynamics inside a single indium phosphide nanowire, allowing them to observe the response with a time resolution in the femtosecond range – or one quadrillionth of a second.

“Basically, we can generate a live picture of how the electrons and holes are excited and slowly return to their original states, and the mechanism behind that can be analyzed and understood,” says Wang, of UC’s Department of Physics. “It’s all critical in characterizing the optical or electronic properties of a semiconducting nanowire.”

Semiconductors are at the center of modern electronics. Computers, TVs and cellphones have them. They’re made from the crystalline form of elements that have scientifically beneficial electrical conductivity properties.

Wang says the burgeoning range of semiconductor nanowire applications – such as smaller, more energy-efficient electronics – has brought rapid improvement to nanowire fabrication techniques. He says his team’s research could offer makers of nanotechnology a new and highly effective option for measuring the physics inside nanowires.

“The key to a good optimization process is an excellent feedback, or a characterization method,” Wang says. “Rayleigh scattering appears to be an exceptional way to measure several nanowire properties simultaneously in a non-invasive and high-quality manner.”

Additional contributors to this research are UC alumnus Mohammad Montazeri; UC physics professors Howard Jackson and Leigh Smith and adjunct associate professor Jan Yarrison-Rice, all of the McMicken College of Arts and Sciences; and Tim Burgess, Suriati Paiman, Hoe Tan, Qiang Gao and Chennupati Jagadish of Australian National University.

You can get more information about the American Physical Society March 3 – 7, 2014 meeting in Denver, Colorado here.

Special coating eliminates need to de-ice airplanes

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There was a big airplane accident years ago where the chief pilot had failed to de-ice the wings just before take off. The plane took off from Dulles Airport (Washington, DC) and crashed minutes later killing the crew and passengers (if memory serves, everyone died).

I read the story in a book about sociolinguistics and work. When the ‘black box’ (a recorder that’s in all airplanes) was recovered, sociolinguists were included in the team that was tasked with trying to establish the cause(s). From the sociolinguists’ perspective, it came down to this. The chief pilot hadn’t flown from Washington, DC very often and was unaware that icing could be as prevalent there as it is more northern airports. He did de-ice the wings but the plane did not take off in its assigned time slot (busy airport). After several minutes and just prior to takeoff, the chief pilot’s second-in-command who was more familiar with Washington’s weather conditions gently suggested de-icing wings a second time and was ignored. (They reproduced some of the dialogue in the text I was reading.) The story made quite an impact on me since I’m very familiar with the phenomenon (confession: I’ve been on both sides of the equation) of comments in the workplace being ignored, although not with such devastating consequences. Predictably, the sociolinguists suggested changing the crew’s communication habits (always a good idea) but it never occurred to them (or to me at the time of reading the text) that technology might help provide an answer.

A Japanese research team (Riho Kamada, Chuo University;  Katsuaki Morita, The University of Tokyo; Koji Okamoto, The University of Tokyo; Akihito Aoki, Kanagawa Institute of Technology; Shigeo Kimura, Kanagawa Institute of Technology; Hirotaka Sakaue, Japan Aerospace Exploration Agency [JAXA]) presented an anti-icing (or de-icing) solution for airplanes at the 65th Annual Meeting of the APS* Division of Fluid Dynamics, November 18–20, 2012 in San Diego, California, from the Nov. 16, 2012 news release on EurekAlert,

To help planes fly safely through cold, wet, and icy conditions, a team of Japanese scientists has developed a new super water-repellent surface that can prevent ice from forming in these harsh atmospheric conditions. Unlike current inflight anti-icing techniques, the researchers envision applying this new anti-icing method to an entire aircraft like a coat of paint.

As airplanes fly through clouds of super-cooled water droplets, areas around the nose, the leading edges of the wings, and the engine cones experience low airflow, says Hirotaka Sakaue, a researcher in the fluid dynamics group at the Japan Aerospace Exploration Agency (JAXA). This enables water droplets to contact the aircraft and form an icy layer. If ice builds up on the wings it can change the way air flows over them, hindering control and potentially making the airplane stall. Other members of the research team are with the University of Tokyo, the Kanagawa Institute of Technology, and Chuo University.

Current anti-icing techniques include diverting hot air from the engines to the wings, preventing ice from forming in the first place, and inflatable membranes known as pneumatic boots, which crack ice off the leading edge of an aircraft’s wings. The super-hydrophobic, or water repelling, coating being developed by Sakaue, Katsuaki Morita – a graduate student at the University of Tokyo – and their colleagues works differently, by preventing the water from sticking to the airplane’s surface in the first place.

The researchers developed a coating containing microscopic particles of a Teflon-based material called polytetrafluoroethylene (PTFE), which reduces the energy needed to detach a drop of water from a surface. “If this energy is small, the droplet is easy to remove,” says Sakaue. “In other words, it’s repelled,” he adds.

The PTFE microscale particles created a rough surface, and the rougher it is, on a microscopic scale, the less energy it takes to detach water from that surface. The researchers varied the size of the PTFE particles in their coatings, from 5 to 30 micrometers, in order to find the most water-repellant size. By measuring the contact angle – the angle between the coating and the drop of water – they could determine how well a surface repelled water.

While this work isn’t occurring at the nanoscale, I thought I’d make an exception due to my interest in the subject.

*APS is the American Physical Society

Canadian scientists get more light in deal with the US Argonne National Laboratory

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Canada’s synchrotron, Canadian Light Source (based in Saskatchewan), has signed a new three-year deal with the US Dept. of Energy’s Argonne National Laboratory’s Advanced Photon Source (APS)  that will give Canadian scientists more access to the APS facilities, according to the June 18, 2012 news item at the  Nanowerk website,

Seeking to solve some of today’s greatest global problems, scientists using x-ray light source facilities at national research laboratories in the United States and Canada are sharing more expertise.

The Canadian Light Source (CLS) and the Advanced Photon Source (APS) at the U.S. Department of Energy’s (DOE’s) Argonne National Laboratory agreed in January 2012 to a Partner User Proposal that cements a stronger working relationship between the two facilities for the next three years. These two premier light sources use different but complementary x-ray techniques to probe materials in order to understand chemical and structural behavior.

Tone Kunz’s June 18, 2012 news release for the APS provides details about the deal,

This new agreement will provide Canadian scientists with more research time to use the x-ray light source facilities and more time on a larger number of APS beamlines. Using varied x-ray and imaging capabilities will broaden the range of experiments Canadians may undertake at the APS to augment their research done at the Canadian Light Source. X-ray science offers potential solutions to a broad range of problems in surface, material, environmental and earth sciences, condensed matter physics, chemistry, and geosciences.

Since the Sector 20 beamlines became fully operational, scientists from Canada and other areas who have used these beamlines at the APS have produced an average of 51 scientific publications a year. This research includes the study of more effective mineral exploration strategies, ways to mitigate mine waste and mercury contamination, and novel ways to fabricate nanomaterials for use in fuel cells, batteries, and LEDs.

I had not realized how longstanding the  CLS/APS relationship has been,

Before the Canadian Light Source began operation in 2004, a Canadian group led by Daryl Crozier of Simon Fraser University, working in partnership with colleagues at the University of Washington and the Pacific Northwest National Laboratory, helped found the Sector 20 beamlines at the APS as part of the Pacific Northwest Consortium Collaborative Access Team, or PNC-CAT. Parts of this team were included in the X-ray Science Division of the APS when it was formed.

This long-standing partnership has led to scientifically significant upgrades to the beamline. The new agreement will provide the valuable manpower and expertise to allow the APS to continue to push the innovation envelope. [emphasis mine]

As I was reading Kunz’s news release I kept asking, what’s in it for the APS? Apparently they need more “manpower and expertise.” Unfortunately, their future plans are a little shy of detail,

Scientists from the APS and the Canadian Light Source will work together on R&D projects to improve light-source technology. In particular, scientists will upgrade even further the two beamlines at Sector 20 in four key areas. This will provide a unique capability to prepare and measure in situ films and interfaces, a new technique to create quantitative three-dimensional chemical maps of samples, and improved forms of spectroscopy to expand the range of elements and types of environments that can be examined.

What are the four key areas? For that matter, what is Sector 20? I suspect some of my readers have similar questions about my postings. It’s easy (especially if you write frequently) to forget that your readers may not be as familiar as you are with the subject matter.

(I wrote about the CLS and another deal with a synchrotron in the UK in my May 31, 2011 posting.)

Inspiring kids, again? High schoolers at Argonne National Laboratory

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C. P. Snow’s 1959 lecture and book, Two Cultures, spends a fair chunk of time on the issue of encouraging the next generation to study science and engineering. As Snow perceived the problem, the UK was falling behind both the US and Russia in the science race. I haven’t investigated what the perceptions were in the US and Russia at the time but I have noticed that descriptions of the race to get someone on the moon feature a great deal of anxiety in the US about Russian supremacy in science. Given human nature, I imagine the Russians were worried too. Plus ça change, n’est ce pas?

Today, everyone is worried that someone else is going to get there (wherever that might be) first and there is enormous pressure internationally to inspire the next generation to pursue science, technology, engineering, and mathematics (STEM) careers.

I see that the Argonne National Laboratory in the US has opened up its doors to high schoolers for a special programme. From the June 6, 2012 news item by Tona Kunz on Nanowerk,

In commencement speeches across the country, graduates have , been warned to expect rocky times breaking into the workforce. Unemployment hovers between 8 and 9 percent. Competition is tough.

Unless you studied science or engineering. Those jobs have a 2 percent unemployment rate, which has led some Fortune 500 companies to complain about offices they can’t fill.

So it’s no surprise that when the U.S. Department of Energy’s (DOE) Argonne National Laboratory decided to give high school students a chance to test-drive a science career, it found students, parents and school officials from Naperville, Ill. eager to hop on board.

Kunz’s June 6, 2012 news release on the Argonne National Laboratory website mentions (Note: I have removed links from the excerpt),

…  Teachers received training in the workings of the Advanced Photon Source (APS), the brightest high-energy X-ray machine in the Western Hemisphere, and the Electron Miscroscopy Center (EMC). Students from Naperville’s two high schools then competed for slots on four research teams that used X-ray beams to decipher what matter is made of, how it’s built and how it reacts.

…

More than 5,000 researchers from throughout the world use the APS and EMC annually to target society’s greatest challenges: how to make better pharmaceuticals, sustainable fuels and high-performance materials. These challenges will feed scientific jobs for decades to come.

“I think there is a huge push in our district from the community for STEM (science, technology, engineering and math) education,” said Tricia Noblett, a teacher and science club advisor at Neuqua Valley High School. “I think they are seizing on what has been out there in the media that STEM fields are where the jobs are and that science careers can be interesting.”

Students drew on experiences in their lives to choose research topics and explained their results to scientists at the annual meeting held in May at Argonne for users of the APS, EMC and Center for Nanoscale Materials (CNM).

…

Inspired by the recent cleanup of a contaminated portion of the west branch of the DuPage River near their school, one group of students studied how to increase the efficiency of water filtration systems.

Another group worked with the Naperville wastewater facility to evaluate how corrosion affects the lifespan of water pipes.

And another group looked at how to improve the efficiency of graphene, a nanomaterial that may hold the key to building faster semiconductors for smart phones and the next-generation of research tools.

It’s exciting stuff and I’m always glad to have a chance to pass on information about these kinds of programmes. As for the history, I find it interesting to note the similarities with and the differences from the past.

Broader Impacts Criterion and informal science education in the US

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Broader Impacts Criterion (BIC), a requirement for US National Science Foundation (NSF) grants covers the areas of science education, science outreach, and the promotion of benefits to society. As you might expect there is support and criticism from scientists and the scientific community about having to include BIC in grant proposals, from the American Physical Society News, June 2007 (volume 16, no. 6),

Bob Eisenstein, Chair of APS’s Panel on Public Affairs, was at NSF when the criterion was first put in place in the mid-1990s. He said that the criterion is meant to serve two purposes: first, it forces scientists to think more carefully about the ways in which their work impacts society, and second, it helps provide the public with more information about what scientists are doing.

Fred Cooper, a current NSF program director for theoretical physics, said his personal opinion is that this is a good thing for NSF to do. “I’m very happy to encourage people to think about these things,” he said. He says it is in scientists’ self-interest to do so.

However, some scientists object to research funding being coupled to education or outreach efforts. Mildred Dresselhaus of MIT says she has heard from many scientists who are unhappy with the broader impacts requirements, and who feel they should be funded based on the quality of their research, not for outreach. …

I gather the criticism was serious enough to warrant a review, excerpted from the July 25, 2011 NISE (Nanoscale Informal Science Education) Net blog posting by Carol Lynn Alpert (BIC requirements have an indirect impact on science museums which benefit from subawards and partnerships with researchers and research institutions seeking to fulfill their BIC obligations),

After reviewing comments from 5,100 stakeholders, the NSB [the National Science Board is the NSF’s governing body] has decided to retain both criteria, but to revise them in order to clarify their intent and “connection to NSF’s core principles” (NSF-11-42, available at http://www.nsf.gov/nsb/publications/2011/06_mrtf.jsp).

As stated by the NSB, these core principles and national goals are led by concerns for global economic and workforce competitiveness, and for the first time allow that “broader impacts” may be achieved “through the research itself.”  This phrase has some worrying that a “BIC loophole” has been created, for it allows that the research itself may be “enough” to enhance U.S economic and workforce competitiveness, without the research team needing to specifically incorporate synergistic activities addressing concomitant K-12 education, diversity, or public engagement goals.

On July 13, AAAS [American Association for the Advancement of Science] submitted a letter to the Chairman of the NSB strongly objecting to what I am here referring to as the “BIC loophole.” AAAS said, “While increasing knowledge serves a public good, it is not always clear how publicly funded research can produce broader impacts unless it is applied and/or widely communicated beyond the scholarly community. The current language appears to offer researchers an excuse not to engage in a more thoughtful consideration of the criterion.”

Here’s a link to the full letter from the AAAS.

I find it fascinating that there’s a discussion about this in the US as the concept of scientists engaging in public outreach does not seem to exist in the same way in Canada. I was able to find Canadian science funding agencies that require some public outreach.  NSERC (Natural Sciences and Engineering Research Council) has a general NSERC policy for public communication,

The Institution [receiving the grant] agrees to:

  1. identify, encourage and assist researchers to communicate with media and participate in announcement events to promote Agency-funded research;
  2. inform, at least five working days before the proposed announcement, if feasible, the Agency’s or Agencies’ public affairs or communications division – normally through the Institution’s own public affairs, communications, or research communications department – of announcements of Agency awards, programs and significant research results that the Institution proposes to make;
  3. include appropriate acknowledgement of the appropriate Agency or Agencies in all relevant public communications issued by the Institution;
  4. respect the relevant Agency or Agencies’ obligation under the Communications Policy of the Government of Canada;
  5. respect the relevant Agency or Agencies’ prerogative to make the first public announcement of its awards, grants and programs, when the relevant Minister declines to do so. It is the purview of a Minister or the Minister’s designate to make public announcements of all federal expenditures; and
  6. share with the Agency or Agencies any promotional material for the general public that is based on Agency-funded research.

So, this NSERC policy is aimed more at the universities and other institutions not the individual researcher.  Also, it seems to be more a guideline or general rule which provides a bit of a contrast  with the Canada Foundation for Innovation (CFI) which lists public communication as a requirement for funding. From the CFI Policy and Program Guide, December 2010,

As part of filing their annual institutional reports (see secion 7.3.2), institutions must provide the CFI with information on the communication activities undertaken in the previous year, along with activities planned for the coming year that are designed to showcase the impacts and outcomes of CFI investments. Institutions are asked to provide information on media activity, publications (print and online) and special events. This information assists the CFI in identifying national trends in research communications, as well as opportunities for collaboration on communications initiatives with institutions. (p. 81)