Terahertz pulse increases electron density 1,000-fold

Findings point to advances in transistor and solar cell development

2011-12-21

(Press-News.org) Kyoto, Japan -- Researchers at Kyoto University have announced a breakthrough with broad implications for semiconductor-based devices. The findings, announced in the December 20 issue of the journal Nature Communications, may lead to the development of ultra-high-speed transistors and high-efficiency photovoltaic cells.

Working with standard semiconductor material (gallium arsenide, GaAs), the team observed that exposing the sample to a terahertz (1,000 gigahertz) range electric field pulse caused an avalanche of electron-hole pairs (excitons) to burst forth. This single-cycle pulse, lasting merely a picosecond (10^-12 s), resulted in a 1,000-fold increase in exciton density compared with the initial state of the sample.

"The terahertz pulse exposes the sample to an intense 1 MV/cm^2 electric field," explains Hideki Hirori, team leader and Assistant Professor at Kyoto University's Institute for Integrated Cell-Material Sciences (iCeMS). "The resulting exciton avalanche can be confirmed by a bright, near-infrared luminescence, demonstrating a three-order of magnitude increase in the number of carriers."

Research in Kyoto using terahertz waves is led by Professor Koichiro Tanaka, whose lab at the iCeMS pursues numerous applications including the development of new biological imaging technologies.

"Since terahertz waves are sensitive to water, our goal is to create a microscope that will allow us to look inside living cells in real time," says Prof. Tanaka. "These just-released results using semiconductors are an entirely different field of science, but they demonstrate the rich potential that lies in the study of terahertz waves."

INFORMATION:

The article, "Extraordinary carrier multiplication gated by a picosecond electric field pulse" by H. Hirori, K. Shinokita, M. Shirai, S. Tani, Y. Kadoya, and K. Tanaka was published online in the December 20, 2011 issue of Nature Communications.

Acknowledgements: This work was supported by Grant-in-Aid for Young Scientists (B) (Grant No. 21760038) of the Japan Society for the Promotion of Science, and also Grant-in-Aid for Scientific Research on Innovative Area "Optical science of dynamically correlated electrons (DYCE)" (Grant No. 20104007) and Grant-in-Aid for Creative Scientific Research (Grant No. 18GS0208) of the Ministry of Education, Culture, Sports, Science and Technology, Japan.

About the iCeMS

The Institute for Integrated Cell-Material Sciences (iCeMS) at Kyoto University in Japan aims to advance the integration of cell and material sciences -- both traditionally strong fields for the university -- in a uniquely innovative global research environment. The iCeMS combines the biosciences, chemistry, materials science, and physics to capture the potential power of stem cells (e.g., ES/iPS cells) and of mesoscopic sciences (e.g., porous coordination polymers). Such developments hold the promise of significant advances in medicine, pharmaceutical studies, the environment, and industry.

[Attachments] See images for this press release:

ELSE PRESS RELEASES FROM THIS DATE:

Jackson Design & Remodeling Wins BBB Torch Award for Marketplace Ethics, the Third Consecutive Win for San Diego Remodeling Company

2011-12-21

Jackson Design & Remodeling (JDR) announced today it has won a 2011 Better Business Bureau (BBB) Torch Award for marketplace ethics in the category for San Diego businesses with 25-99 employees. The company won BBB awards in 2007 and 2009. Winning companies are only eligible to submit entries every two years, making this JDR's third consecutive win. The Torch Awards are the BBB's annual awards program honoring outstanding local for-profit companies and nonprofit charitable organizations that have demonstrated a commitment to ethical business practices, both in operations ...

Frankincense production 'doomed' warn ecologists

2011-12-21

Trees that produce frankincense – used in incense and perfumes across the world and a key part of the Christmas story – are declining so dramatically that production of the fragrant resin could be halved over the next 15 years, according to a new study published in the British Ecological Society's Journal of Applied Ecology. Ecologists from the Netherlands and Ethiopia say tree numbers could decline by 90% in the next 50 years. If fire, grazing and insect attack – the most likely causes of the decline – remain unchecked frankincense production could be doomed, they warn. ...

Every cloud has a silver lining: Weather forecasting models could predict brain tumor growth

2011-12-21

Every cloud has a silver lining: weather forecasting models could predict brain tumor growth Ever wondered how meteorologists can accurately predict the weather? They use complex spatiotemporal weather models, i.e. mathematical equations that track the motions of the atmosphere through time and space, and combine them with incoming data streams from weather stations and satellites. Now, an innovative new study published in BioMed Central's open access journal Biology Direct has determined that the mathematical methodology used to assimilate data for weather forecasting ...

Get ready for spring - hay fever worse in spring than summer

2011-12-21

Hay fever (runny nose, sneezing, itchy eyes) is caused by an allergy to pollen, and most commonly to grass pollen. These tiny grains bring misery to sufferers through spring and summer and pollen levels are often included as part of weather reports to help sufferers prepare. However new research published in BioMed Central's open access journal Clinical and Translational Allergy shows that, regardless of medication and other allergies, for the same grass pollen levels, hay fever symptoms are worse in the first half of the season than later on. Worldwide there are over ...

New candidate vaccine neutralizes all tested strains of malaria parasite

2011-12-21

A new candidate malaria vaccine with the potential to neutralise all strains of the most deadly species of malaria parasite has been developed by a team led by scientists at the University of Oxford. The results of this new vaccine independently confirm the utility of a key discovery reported last month from scientists at the Wellcome Trust Sanger Institute who had identified this target within the parasite as a potential 'Achilles' heel' that could hold significant promise for vaccine development. According to the World Malaria Report 2010, malaria killed an estimated ...

Can nerve growth factor gene therapy prevent diabetic heart disease?

2011-12-21

Diabetes is a major risk factor for cardiovascular disease and can reduce blood supply to the heart tissue and damage cardiac cells, resulting in heart failure. New research has investigated if nerve growth factor (NGF) gene therapy can prevent diabetic heart failure and small vascular disease in mice. The study by Professor Costanza Emanueli, British Heart Foundation Senior Research Fellow and colleagues of the Bristol Heart Institute in the Regenerative Medicine Section of the School of Clinical Sciences at the University of Bristol is published online in Diabetes, ...

Fame is more likely to kill rock stars, not being 27 years old

2011-12-21

The list of well known musicians who have died at age 27 may look like more than a coincidence – Amy Winehouse, Jim Morrison, Jimi Hendrix, Janis Joplin, Kurt Cobain, and Brian Jones to name a few – but their age is unlikely to have been the cause of their demise, according to research in the Christmas issue published on bmj.com today. While fame may increase the risk of death for musicians, probably due to their rock and roll lifestyle, this risk is not limited to age 27, say the authors led by Adrian Barnett from Queensland University of Technology in Australia. To ...

Salt policy makers eat too much salt at work

2011-12-21

Salt policy makers in the Netherlands are consuming more than the average daily recommended salt intake of 6 grams in one hot meal at their work canteens, finds a study in the Christmas issue published on bmj.com today. The authors, led by Dr Lizzy Brewster at the University of Amsterdam, say the policy makers eating at their staff canteens were consuming around 15.4 grams of salt a day. They warn that this amount of salt, compared to the recommended intake, translates to up to a 36% increase in premature death. Excess salt intake is estimated to cause 30% of all high ...

Doctors should stop using the phrase 'obs stable' in hospital notes

2011-12-21

The phrase "obs stable" in hospital notes is ambiguous and does not reliably indicate a patient's health status, concludes a study in the Christmas issue published on bmj.com today. Dr Gregory Scott and colleagues argue that the phrase is potentially misleading and advise doctors to stop using it and write the observations in full. The expression "obs stable" is written daily in hospital notes to indicate that there are no alarming problems with a patient's bedside nursing observations. Abnormalities in these observations act as an alarm for doctors when assessing ...

Could cod liver oil help combat tuberculosis?

2011-12-21

A review of a historical study from 1848 reveals that cod liver oil was an effective treatment for tuberculosis, says Professor Sir Malcolm Green in the Christmas issue published on bmj.com today. In the study, carried out by physicians at the Hospital for Consumption, Chelsea (now the Royal Brompton Hospital), 542 patients with consumption (tuberculosis) received standard treatment with cod liver oil. These patients were compared with 535 'control' patients who received standard treatment alone (without cod liver oil). While improvement rates were similar in the two ...

LAST 30 PRESS RELEASES:

Evaluating performance and agreement of coronary heart disease polygenic risk scores

Heart failure in zero gravity— external constraint and cardiac hemodynamics

Amid record year for dengue infections, new study finds climate change responsible for 19% of today’s rising dengue burden

New study finds air pollution increases inflammation primarily in patients with heart disease

AI finds undiagnosed liver disease in early stages

The American Society of Tropical Medicine and Hygiene and the Bill & Melinda Gates Foundation announce new research fellowship in malaria genomics in honor of professor Dominic Kwiatkowski