Until now, the complexity of PMN-PT has thwarted researchers' efforts to develop simple, reproducable microscale fabrication techniques.
Applying microscale fabrication techniques such as those used in computer electronics, Eom's team has overcome that barrier. He and his colleagues worked from the ground up to integrate PMN-PT seamlessly onto silicon. Because of potential chemical reactions among the components, they layered materials and carefully planned the locations of individual atoms. "You have to lay down the right element first," says Eom.
Onto a silicon "platform," his team adds a very thin layer of strontium titanate, which acts as a template and mimics the structure of silicon. Next comes a layer of strontium ruthenate, an electrode Eom developed some years ago, and finally, the single-crystal piezoelectric material PMN-PT.
The researchers have characterized the material's piezoelectric response, which correlates with theoretical predictions. "The properties of the single crystal we integrated on silicon are as good as the bulk single crystal," says Eom.
His team calls devices fabricated from this giant piezoelectric material "hyper-active MEMS" for their potential to offer researchers a high level of active control. Using the material, his team also developed a process for fabricating piezoelectric MEMS. Applied in signal processing, communications, medical imaging and nanopositioning actuators, hyper-active MEMS devices could reduce power consumption and increase actuator speed and sensor sensitivity. Additionally, through a process called energy harvesting, hyper-active MEMS devices could convert energy from sources such as mechanical vibrations into electricity that powers other small devicesfor example, for wireless communication.
The National Science Foundation is funding the research via a four-year, $1.35 million NIRT grant. At UW-Madison, team members includ
|Contact: Chang-Beom Eom|
University of Wisconsin-Madison