April 11, 2011

By Audrey Rabalais

The same semiconductor that lights up traffic signals is being harnessed by a researcher at Ohio University to store information in modern electronics.

Kangkang Wang, a PhD student and research assistant in OU's Nanoscale and Quantum Phenomena Institute (NQPI), presented his research on two-dimensional manganese structures on the gallium nitride growth surface to members of NQPI on Friday, February 11.

Wang has spent the last year and a half manipulating the two elements to create a thin magnetic film that rests on a semiconductor. With these, he creates the possibility of using the spin of the electrons involved to store data in electronic devices. Older technology becomes a problem when electronics shrink in size due to increased power consumption per unit volume which causes overheating and wasted energy. By using electrons rather than magnets or other materials, these electronic devices become smaller, smarter versions of their ancestors. This field of study is known as spintronics.

“Spintronics is said to be offering advantages of higher processing speed, reduced power consumption, nonvolatility and increased density of storage,” said Wang. “Spintronics is not really a brand new idea. It has already been implemented in several electronic applications such as hard drives.”

Wang chose gallium nitride and manganese because their combinative properties make controlling and moving the electrons easy. Gallium nitride is a semiconductor and manganese is a ferromagnet when coupled with gallium. Manganese can be grown in a crystalline structure on top of GaN, without combining with it, allowing scientists to finely manipulate the spin of the electrons. The two elements form alloys with stable magnetic properties, which means the spin structure of the atoms is also stable.

“If we can prepare some of these atoms with very well-defined spin structure, we can manipulate the spin as we wish. Then we can possibly make use of the spin to store some information,” Wang said.

By using a scanning tunneling microscope (STM), Wang and other researchers can visualize the layout of the atoms so in the future they can move and manipulate them at will. However, for this project, Wang did not have technology that could keep up with his lofty research plans. He spent much of his time updating old equipment and building a completely new, spin-polarized STM.

“We are doing frontier research in science, so we often have to build our machines,” said Saw-Wai Hla, Associate Professor of Physics. “If you are at the highest point of a skyscraper, you still want to go up higher, so you have to set up your own ladder to climb up.”

Wang said the project was completely finished in November 2010. In October 2010, he won the Leo M. Falicov Student Award for his work at the AVS 57th International Symposium & Exhibition. The prestigious award is given to one student every year and includes $1000 cash. Wang's research has been accepted for publication in the Physical Review B Journal of the American Physical Society.