Graduate Discovers Record Low Pressure-induced Phase Transition in a Semiconductor

Anya Rasmussen’s Research Published in Peer-Reviewed Physics Journal

By: Camlynne Waring

Rasmussen (right) and and fellow researcher Elham Mafi (left) taking a Raman spectrum of indium selenide at high pressure. Photo credit: Shelly Hanks

Recent Walla Walla University alumna Anya Rasmussen and fellow researchers at Washington State University recently discovered a pressure-induced phase transition in indium selenide at the pressure of seven tenths of a gigapascal (GPa), which is believed to be the lowest critical pressure observed in a semiconductor.  Their research has been published in Applied Physics Letters, a peer-reviewed scientific journal published by the American Institute of Physics.

“This critical pressure is an order of magnitude lower than that for most materials,” says Rasmussen. “Other semiconductors show phase transitions at two GPa or higher.”

Rasmussen’s research could have implications for memory devices, called phase change random access memory, or PRAM.  PRAM is a faster and smaller replacement for FLASH memory.  Indium selenide is a phase change material that can be used in these devices.

“The switching in PRAM devices is done thermally,” explains Rasmussen. “However, the thermal phase transitions can cause the phase change material to change in volume, which puts stress on the material possibly affecting the memory switching. To precisely control switching between phases, it is important to understand the phase transformations due to pressure as well as temperature.”

Rasmussen is a doctoral candidate at Washington State University, with full funding provided by a grant from the National Science Foundation.

Rasmussen’s WWU education gave her the skills she needed to succeed in her graduate studies. “WWU's physics instruction prepared me well for graduate level physics classes,” says Rasmussen. “I am grateful for such a strong math background, as I also majored in math at WWU.”  Her experience as a teaching assistant for the applied statistics class also gave Rasmussen a strong background in probability, which was beneficial in her graduate thermodynamic course work.

In the future, Rasmussen hopes to teach physics at a college or university and continue her research on high pressure physics.

apl.aip.org/resource/1/applab/v102/i6/p062105_s1

 

Published May 30, 2013

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