Electronic Materials Synthesis the Topic of 2016 Nelson Lecture
On March 31, the Department of Materials Science and Engineering hosted the 2016 Nelson W. Taylor Lecture in Materials, presented by Nobel Laureate Shuji Nakamura.
Before taking the podium in front of an overflow crowd in the HUB-Robson Center, the 2014 Physics Laureate was preceded by three Penn State faculty experts discussing their work involving the synthesis of electronic materials.
Roman Engel-Herbert, assistant professor of materials science and engineering, presented a talk titled “New opportunities in electronic materials utilizing strong electron correlation effects,” in which he discussed recent efforts to develop transparent metal conductors. Using a hybrid molecular beam epitaxy deposition technique, he described ways to open new growth windows – the conditions under which a material can be epitaxially grown on a substrate in a self-regulated fashion – in transition metal oxides using volatile precursors.
Engel-Herbert successfully grew transparent metal thin films using what he referred to as the “hidden knob” of electron correlation, which is a quantum phenomenon in which electrons become entangled, increasing their effective mass, thus making them transparent in the visible spectrum. This unusual electronic material is a potential candidate to replace indium tin oxide for smart phone, tablet, and TV displays.
John Badding, professor of chemistry, physics and materials science and engineering, spoke on “confined geometry chemical deposition for next generation optoelectronics.” Badding’s technology uses high pressure chemical vapor deposition to grow semiconductor materials inside optical fibers with multiple smaller pores. Like long silicon threads, these materials can be used as infrared lasers, wave guides for optoelectronics or long range electron transport though quantum confinement. Using other geometries besides optical fibers, Badding and Penn State colleague Venkat Gopalan can make films, amorphous silicon solar cells, large-area single crystals and possibly do hundreds of meters of materials deposition for large-area electronics, replacing expensive plasma reactors.
Adri van Duin
Adri van Duin, professor of mechanical and nuclear engineering, spoke on “the reactive force field method and its application to CVD growth.” ReaxFF is a computational method that uses empirical approximations to expand small scale atomistic calculations to the million-atom scale. ReaxFF, which van Duin developed in collaboration with Bill Goddard (Caltech) and others, is a bond-order based empirical force field. Penn State, van Duin said, is in a good position to cover all of the size scales required in materials simulation. The Materials Computation Center that he directs at Penn State brings together almost two dozen faculty experts in virtually every field of theory and simulation. “New deposition techniques require new, more complex calculations and simulation,” he said.
The Taylor Lecturer, Professor Shuji Nakamura of the University of California, Santa Barbara, was introduced by Susan Sinnott, head of the Department of Materials Science and Engineering.
In “The invention of high efficient blue LEDs and future lighting,” Nakamura told the amusing tale of how he came to invent one of the most important energy saving technologies of the 20th century.
Nakamura graduated from the University of Tokushima in 1979 after earning a Master’s degree, the highest degree the university offered. He went to work at a small chemical company in the same city, where he was assigned to develop a red light emitting diode.
“The University of Tokushima had the lowest ranking of all universities in Japan. It’s located in a remote city. I joined a small company that had no background in semiconductors, but my boss asked me to develop a conventional red LED. So, I had to spend 10 years developing these conventional red LEDs. But other companies were already making this product. Even if I could make it, no one would buy it from this small chemical company,” he said to laughter from the standing-room-only crowd.
After 10 years of work, Nakamura was so dispirited he was ready to quit. His work had not produced a single sale, and his boss frequently complained that he had cost the company a lot of money. As a last resort, he went to the founder and president of the company and told him he wanted to work on a blue LED. This was something that large teams of Ph.D. scientists from top universities were working on at large electronic companies like Panasonic and Sony with budgets of $100 million for three years.
“I was one person, no money, no Ph.D.,” Nakamura said. “When I told our founder I wanted to work on a blue LED, he said ‘OK.’ He was 75 years old, I thought he didn’t understand what I meant.
“I said, ‘Will you give me money for research?’ He said, ‘No problem.’
“I had never been to another country. I asked him, ‘Can I go to the University of Florida for one year?’ And again he said, ‘No problem.’
“So, I went to the University of Florida for one year, from ’88 to ’89, and when I came back I went to work on the blue LED.”
Within four years, he had invented the first blue LED based on a material, gallium nitride, that no one thought could work.
Nakamura has gone on to win many other awards, earned a Ph.D., and moved to the U.S. in 2000. The white LEDs that resulted from his research have made a substantial dent in energy usage, the equivalent of 19 nuclear power plants over five years in the U.S. alone, he estimates.
By combining low energy white LEDs with solar cells, his discoveries have brought low cost lighting to areas of the world without an electrical grid.
Recent discoveries about potential danger from long exposure to the strong blue emissions in white LEDs surprised Nakamura. However, the news more than justifies his switch away from his invention toward developing the safer, more natural light of violet LEDs. His company, cofounded with two UCSB colleagues in 2008, is the world’s only manufacturer of violet-based white LEDs.
The man who famous professors once called “some crazy guy at some company working on gallium nitride” (a material they just knew would never work) now holds more than 200 U.S. patents and 300-plus Japanese patents and has published more than 550 scientific papers. Pretty good for a guy who had yet to publish a single paper by the age of 35.
The Nelson W. Taylor Lecture Series in Materials Science and Engineering honors the memory of Professor Taylor (1869-1965) who was head of Penn State’s Department of Ceramics from 1933-1943.