WFU hosts international excitonic processes conference

By Jacob McConnico
June 5, 2006

The process used to illuminate a television or computer screen or the technology behind elaborate optical fiber telecommunications systems or advertising displays might not be of much concern to the average person, but when a display breaks down or looks outdated or communications fail, it becomes a big issue for even the most non-scientific minds.

A desire to understand, improve and further manipulate the science of converting light to excited electrons and the conversion of excited electrons back to light in various materials is the reason more than 115 researchers from at least 18 different countries will converge at Wake Forest University for the 7th International Conference on Excitonic Processes in Condensed Matter June 26-30.

Richard Williams, Reynolds Professor of Physics at Wake Forest and conference chairman, said the event brings together researchers from a variety of basic and applied fields and offers a unique opportunity for the participants to discuss their work.

"This international scientific gathering places Wake Forest among an elite list of institutions and cities around the world that have hosted this conference," said Williams, who is the author of numerous articles and a book about excitons and is a member of the international advisory committee for the EXCON series. "Though excitons may not be a familiar term to many, they really affect us every day in important ways for economics and living."

An exciton is a bound state of an electron and the absence of an electron called an "electron hole" in an insulator or semiconductor.

Excitons produce the light in light emitting diodes or LEDs and in laser diodes found in CD players, grocery store scanners and laser pointers. They may also play a role in future quantum computer technologies.

Excitons are at the heart of modern laser diodes used in optical communications and optical memories. They also play a role in processes important to our lives and health such as photosynthesis, vision and radiation damage such as from sunburn and X-ray exposure.

Some of the research to be reported during EXCON 2006 at Wake Forest looks at excitons in nanoscale structures — quantum dots, quantum wires, and quantum wells — for insight on new opportunities and devices. Novel advances to be described include a semiconductor source of photon pairs in entangled quantum states and spin-injection in quantum wells, both looking toward new generations of computing. Reports will detail theoretical advances in understanding the exciton's role in radiation damage.

The study of excitons and how they behave also has wide implications in the development of inorganic and organic light emitters for different types of displays - personal computer screens, cell phones, televisions and many other electronic devices.

Inorganic semiconductor light emitters like gallium arsenide, indium arsenide and gallium phosphide are essential in optical fiber telecommunications, CD players and some video displays, and they offer a bright and energy efficient future alternative to incandescent lighting. But, such materials are typically rigid and brittle, making them inappropriate for flexible electronics.

Organic semiconductors offer an attractive alternative because they are easy to make, emit visible light and can be manipulated more easily. Researchers around the world have developed a range of organic-semiconductor devices, including transistors, LEDs, solar cells and lasers. Excitons are an important aspect to be mastered for these applications.

The Japanese have been particularly adept in recent years at developing excitonic processes for use in technology. More than 60 of the conference participants are from Japan.

The series of conferences, also known as EXCON, are held in even number years and started in 1994 in Darwin, Australia. This is only the second time the conference has been held in the United States. Previous conference sites have included Kurort Gohrisch, Germany; Boston; Osaka, Japan; and Cracow, Poland.

Advance registration is required for all conference participants. For more information about EXCON 2006, please visit the conference Web site: