Portland, Ore. - A team at Central Michigan University (Mount Pleasant) is striving toward a model that will let designers build application-specific piezoelectric semiconductors.
Those adding such semiconductors to their designs today basically choose from among the known piezoelectric materials available off the shelf, said assistant professor of physics Marco Fornari.
Fornari has spent more than two years working with various colleagues to gather the mother of all piezoelectric data sets. Armed with a Cottrell College Science Award, granted in November, he is now building a model from that data set that will enable designers to create application-specific piezoelectric semiconductors. Fornari expects to show off the first example this fall.
"We want our model to predict the electrical properties of novel new materials by interpreting the huge amount of data that we have already gathered from several good candidate materials-materials that we have already synthesized in the lab and have been testing over the last few years," said Fornari. "Now we are building a model which understands why they are so good, and with it we can design even better properties into novel nanoscale materials."
Fornari hopes to have designed at least one nanoscale material before this year's fall conference schedule commences. He then plans to continue refining his model into 2006, when he hopes to deliver a field-tested tool that enables designers to create custom-formulated piezoelectric materials for any application-from actuator to electric motor.
"There are many different types of properties to utilize for specific applications, such as for random-access memories or for different types of sensors or transducers," said Fornari. "Today we know how to make different sorts of piezoelectric materials, but it is not clear what happens to those effects when you scale them down. With our model, we hope to be able to design better materials at the nanoscale, with no preset limit on what you can design. You will use a new composition every time you use the tool, covering all types of parameters, such as making a wider temperature range or a more specific frequency, or many other properties for special requirements."
Fornari and his colleagues have already formulated several novel materials in the lab, ones designed to enable a range of capabilities. His favorite candidate material is perovskite and its alloys. In nature, perovskite is composed of calcium, titanium and oxygen, but often with a mixture of rare-earth metals too, such as zirconium and lead.
Fornari's favorite formulation so far is zirconium, titanium, lead and oxygen. By modeling these four ingredients, and the precise results from different mixes along with various dopants, Fornari hopes to create and synthesize novel compounds with nanoscale properties that optimize each application with a unique semiconductor formulation.
"We want to model which properties are important when producing different piezoelectric effects, so that we can design-in really nice properties at the nanoscale," said Fornari.
Piezoelectric semiconductors transduce acoustic vibrations into electricity and vice versa. Thus they can be used for both emitters (such as speakers) and detectors (such as microphones). They can also be used as actuators, to drive anything from a robot's arm to a lithographic mask aligner, and in sonography. Fornari thinks that his model will demonstrate how to custom-formulate materials for each application.