AZ Partners in Science - 2013
Spin-dependent transport of electrons in magnetic tunneling junctions
Creating Next-Generation Transistors
There is an urgent need to solve the problem of excessive energy consumption in next-generation transistors. It is caused by greatly increased current leakage when transistor size is reduced below 10 nm. (A nanometer is almost unimaginably small -- one-billionth of a meter.)
If no solution is found, according to one prediction, transistors used in information technology could gobble up to 20 percent of the world’s electricity by 2025.
Sadequn Nahar, Sunnyside High School, is working with Associate Professor Weigang Wang, UA Department of Physics, to find a technological fix.
Nahar’s research, funded by a Partners in Science Award from Research Corporation for Science Advancement, is focused on exploiting spin-based magnetic nanostructures. Electrons carry a charge, positive or negative, but they also have a quality called “spin,” which comes in two modes – up or down. (Electron spin in atoms is the main source of ferromagnetism.)
“Spintronics” – rather than “electronics” -- could solve the leaky current problem in transistors. However, the power consumption required to switch spin modes is relatively high. Nahar is looking at novel mechanisms to dramatically reduce magnetization reversal energy.
She has been testing various magnetic tunneling junctions (MTJs). These incredibly tiny devices consist of two magnetic layers separated by an ultrathin oxide layer (1 nm – 2 nm). Electrons can tunnel through the oxide barrier under a bias voltage. The resistance of the system depends on the relative orientation of the magnetic layers. Generally the resistance is low if the magnetizations of two magnetic layers are parallel (P state) and the resistance is high if the magnetizations are antiparallel (AP) state.
Nahar is exploring mechanisms that increase the resistance difference in the P and AP states.
“Our goal is to fabricate a sample that can give us a resistance of better than 300 percent,” she said. “We haven’t gotten there yet, but the research continues. The other thing we want to achieve is consistency, to reproduce samples the yield the same effects every time. We haven’t achieved that yet.”
Nahar said some of her Sunnyside High students have shown an interest in her work. “I’m expecting them to visit this lab,” she said. “And we have a chapter on electricity and magnetism, which fits nicely into this research. Also, Dr. Wang is open to recruiting some of my good students to work in his lab, and he’s willing to visit my class to give a talk.”