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Lasers, sensors, diagnostics
Team perfecting million-dollar crystals … and WSU program
Friday, Feb. 17, 2012
By Tina Hilding, College of Engineering and Architecture
Kelvin Lynn (Photo by Robert Hubner, WSU Photo
PULLMAN, Wash. - A beautifully formed single silicon crystal sits in the Washington State University office of professor Kelvin Lynn. Add Intel chips to it, and the large wafer of silicon is worth about $5 million.
Nearby is a seemingly perfect crystal of fluorescent yttrium aluminum garnet (YAG). Add a little cerium and it can be used in radiation detectors; it glows when hit with radiation and also can be used in medical diagnostics. A nearby purple crystal, neodymium YAG, when used to produce a laser, can cut all the metal in your car, Lynn said.
A good crystal of cadmium zinc telluride (CdZnTe), transparent to infrared radiation but not to visible light, allows you to detect thermal or radiation signatures clearly. From the sky, you might be able to see molecules in smoke coming from a factory that is miles below. You might detect radiation at a border crossing or see the tiny beginnings of a cancer in a laboratory.
Basic science of growing studied
Lynn is Boeing chair of advanced materials, George and Diane Conniff distinguished professor and director of the WSU Center for Materials Research. He and his colleagues in the CMR are helping industries around the world with the challenge of growing better crystals.
Although lasers were invented almost 50 years ago and are used in everything from missile guidance to eye surgery, growing the crystals that are used in solid state lasers has never been an exact science.
Because of the prohibitive cost of growing them, little research has been conducted on the basic science of the methods used. When Lynn arrived at WSU about 15 years ago from Brookhaven National Laboratory, he saw the need.
Washington leads in crystals
Washington grows more crystal materials than any other state. For example, REC Silicon Inc., based in Moses Lake, is one of the largest producers of silicon materials in the world for the solar industry.
The industry is made possible by the continuous and inexpensive hydropower along the Columbia River, Lynn said. If you’re a crystal grower and you lose power, you lose your crystal and probably your profit for an entire year.
Figuring variables to optimize quality
CMR researchers work with industry leaders to grow and characterize crystals that are used for civil and military laser applications. The researchers are working to improve crystal growth of YAG, which they hope will lead to more efficient, high-powered, smaller sized and lighter weight lasers. They are trying to improve CdZnTe crystals for use as radiation detectors in medical imaging and handheld instruments.
The researchers are working to better understand and improve silicon crystal growth by assessing damage and defects that occur in the industrial process and mitigating them.
The researchers buy powder for their crystals and then heat them in specially built furnaces. Temperatures might range from 1,450 to more than 2,000 degrees centigrade. Growing some of the world’s best crystals can take a few days or several weeks.
"We figure out the right environment, the right dopants (additives) and the right growth rate,” said Lynn.
Science ‘the ultimate adventure’
Originally from South Dakota, Lynn had an early interest in math and science. Math, he said, "is elegant.” In new science, he said, "nobody knows the answers.”
"It’s the ultimate adventure. It’s a real exciting drive to solve something that no one else has solved,” he said.
When he entered college, he studied a variety of math and science topics, including materials science, physics, chemical engineering, chemistry, engineering and math. At one time, he considered getting a degree in philosophy. He finally settled on degrees in math and materials science and engineering.
He came away from his education with the feeling that the distinct fields "were all related, although they were taught differently.”
After getting his doctorate, Lynn worked at Brookhaven as a physicist and materials scientist. There he conducted pioneering research in the design of positron beams and constructed the first prototype.
Lynn is a fellow of the American Association for the Advancement of Science (AAAS) as well as the American Physical Society. His work has been extensively cited around the world.
Program, reputation growing
Lynn was drawn to WSU partly because of the reputation of Professor John Hirth and the materials science program, which, he said, was uniquely integrated at the graduate level. It included physicists, engineers and chemists.
In addition to his work in crystals, Lynn is internationally renowned for his pioneering research on positrons. He is developing a trap for the tricky antimatter particles, which want to annihilate the instant they run up against matter, and is using them to characterize defects embedded deep inside materials.
And Lynn continues to build materials research capability at WSU into a truly interdisciplinary effort. The university’s material science and engineering graduate program is growing, the number of students is increasing, and the program’s reputation is on the upswing.
Lynn hopes to develop a research center focused particularly on using new materials as sensors, including radiation detectors. This would include high-level materials science research in crystal growth and systems, as well as in electronics, packaging and forensics.
Difficult process, rewarding benefits
The work is sometimes difficult. Lynn is embarrassed that it took him and his colleagues so long to figure out positron traps—which, he said, "are so simple.” Then, it took another few years, with plenty of rejection, to get support for his ideas.
Sometimes, scientific discussions around a research point can become "scientific shouting,” he said wryly.
But the work that this integrated team is doing has the ability to change the world, Lynn said. The work has been supported by a host of sponsors at an average annual research expenditure of nearly $2 million during the past decade. Sponsors include the National Science Foundation, U.S. Department of Energy, various agencies of the U.S. Department of Defense and the private sector.
Lynn’s colleagues, many of whom he has helped and mentored over the years, consider him an intellectual tour de force and a "man with a million ideas.”
"I do science because I really love it,” Lynn said. "When I use my creative energy to do better science, I do just fine. And everyone else, hopefully, benefits too.”