Tag Archives: American Physical Society

New method of Rayleigh scattering for better semiconductors

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

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

Broader Impacts Criterion and informal science education in the US

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)