November 21, 2011 — University of Wisconsin-Madison engineers and physicists have integrated highly piezoelectric single-crystal material onto silicon to fabricate a low-voltage, micro electro mechanical system (MEMS) for communications, energy harvesting, sensing, actuators and other applications.
Chang-Beom Eom, UW-Madison professor of materials science and engineering and physics, led a team studying lead magnesium niobate-lead titanate (PWN-PT), which possesses piezoelectric properties that deliver much greater mechanical displacement with the same amount of electric field as traditional piezoelectric materials.
Rather than starting with bulk piezoelectric material and grinding it down to use in the nearly nanoscale device, the UW-Madison team layered PMN-PT onto silicon using wafer fabrication techniques. The atomic-level fabrication control prevented chemical reactions among components.
Onto a silicon substrate, Eom’s team adds a very thin layer of strontium titanate, which acts as a template and mimics the structure of silicon. Next, a layer of strontium ruthenate as electrode, 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 are as good as the bulk single-crystal material, Eom said.
The resultant devices are called hyper-active MEMS, because active control is high. The material can also be used for fabricating piezoelectric MEMS.
Applied in signal processing, communications, medical imaging and nanopositioning actuators, hyperactive MEMS devices could reduce power consumption and increase actuator speed and sensor sensitivity. Additionally, through a process called energy harvesting, hyperactive MEMS devices could convert energy from sources such as mechanical vibrations into electricity that powers other small devices-for 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 include Lynn H. Matthias Professor in Electrical and Computer Engineering Robert Blick and physics professor Mark Rzchowski. Other collaborators include people at the National Institute of Standards and Technology, Pennsylvania State University, the University of Michigan, Argonne National Laboratory, the University of California at Berkeley, and Cornell University.
The multi-institutional team published its results in the November 18 issue of the journal Science. Access it here: http://www.sciencemag.org/content/334/6058/958.short.