Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Technique Creates Piezoelectric Ferroelectric Nanostructures

23.02.2012
Researchers have developed a “soft template infiltration” technique for fabricating free-standing piezoelectrically active ferroelectric nanotubes and other nanostructures from PZT – a material that is attractive because of its large piezoelectric response. Developed at the Georgia Institute of Technology, the technique allows fabrication of ferroelectric nanostructures with user-defined shapes, location and pattern variation across the same substrate.

The resulting structures, which are 100 to 200 nanometers in outer diameter with thickness ranging from 5 to 25 nanometers, show a piezoelectric response comparable to that of PZT thin films of much larger dimensions. The technique could ultimately lead to production of actively-tunable photonic and phononic crystals, terahertz emitters, energy harvesters, micromotors, micropumps and nanoelectromechanical sensors, actuators and transducers – all made from the PZT material.

Using a novel characterization technique developed at Oak Ridge National Laboratory, the researchers for the first time made high-accuracy in-situ measurements of the nanoscale piezoelectric properties of the structures.

“We are using a new nano-manufacturing method for creating three-dimensional nanostructures with high aspect ratios in ferroelectric materials that have attractive piezoelectric properties,” said Nazanin Bassiri-Gharb, an assistant professor in Georgia Tech’s Woodruff School of Mechanical Engineering. “We also leveraged a new characterization method available through Oak Ridge to study the piezoelectric response of these nanostructures on the substrate where they were produced.”

The research was published online on Jan. 26, 2012, and is scheduled for publication in the print edition (Vol. 24, Issue 9) of the journal Advanced Materials. The research was supported by Georgia Tech new faculty startup funds.

Ferroelectric materials at the nanometer scale are promising for a wide range of applications, but processing them into useful devices has proven challenging – despite success at producing such devices at the micrometer scale. Top-down manufacturing techniques, such as focused ion beam milling, allow accurate definition of devices at the nanometer scale, but the process can induce surface damage that degrades the ferroelectric and piezoelectric properties that make the material interesting.

Until now, bottom-up fabrication techniques have been unable to produce structures with both high aspect ratios and precise control over location. The technique reported by the Georgia Tech researchers allows production of nanotubes made from PZT (PbZr0.52Ti0.48O3) with aspect ratios of up to 5 to 1.

“This technique gives us a degree of control over the three-dimensional process that we’ve not had before,” said Bassiri-Gharb. “When we did the characterization, we saw a size effect that until now had been observed only in thin films of this material at much larger size scales.”

The ferroelectric nanotubes are especially interesting because their properties – including size, shape, optical responses and dielectric characteristics – can be controlled by external forces even after they are fabricated.

“These are truly smart materials, which means they respond to external stimuli such as applied electric fields, thermal fields or stress fields,” said Bassiri-Gharb. “You can tune them to behave differently. Devices made from these materials could be fine tuned to respond to a different wavelength or to emit at a different wavelength during operation.”

For example, the piezoelectric effect could permit fabrication of “nano-muscle” tubes that would act as tiny pumps when an electric field is applied to them. The fields could also be used to tune the properties of photonic crystals, or to create structures whose size can be altered slightly to absorb electromagnetic energy of different wavelengths.

In fabricating the nanotubes, Bassiri-Gharb and graduate student Ashley Bernal (currently an assistant professor at the Rose-Hulman Institute of Technology) began with a silicon substrate and spin-coated a negative electron-beam resist material onto it. A template was created using electron-beam lithography, and a thin layer of aluminum oxide was added on top of that using atomic layer deposition.

Next, the template was immersed under vacuum into an ultrasound bath containing a chemical precursor solution for PZT. The structures were pyrolyzed at 300 degrees Celsius, then annealed in a two-step heat treating process at 600 and 800 degrees Celsius to crystallize the material and decompose the polymer substrate. The process produced free-standing PZT nanotubes connected by a thin layer of the original aluminum oxide. Increasing the amount of chemical infiltration allows production of solid nanorods or nanowires instead of hollow nanotubes.

Though the researchers used electron beam lithography to create the template on which the structures were grown, in principle, many other chemical, optical or mechanical patterning techniques could be used for create the templates, Bassiri-Gharb noted.

In studies done in collaboration with researchers Sergei Kalinin and Alexander Tselev of the Center for Nanophase Materials Sciences at the Oak Ridge National Laboratory, the devices produced by the soft template process were analyzed with band-excitation piezoresponse force microscopy (BPFM). The technique allowed researchers to isolate properties of the AFM tip from those of the PZT sample, allowing analysis in sufficient detail to detect the size-scale piezoelectric effects.

“One of our most important observations is that these piezoelectric nanomaterials allow us to generate a factor of four to six increase in the extrinsic piezoelectric response compared to the use of thin films,” said Baassiri-Gharb. “This would be a huge advantage in terms of manufacturing because it means we could get the same response from much smaller structures than we would have had to otherwise use.”

The Center for Nanophase Materials Sciences is one of the five Department of Energy (DOE) Nanoscale Science Research Centers, premier national user facilities for interdisciplinary research at the nanoscale that are supported by the DOE Office of Science. Together, the NSRCs comprise a suite of complementary facilities that provide researchers with state-of-the-art capabilities to fabricate, process, characterize and model nanoscale materials, and constitute the largest infrastructure investment of the National Nanotechnology Initiative. The NSRCs are located at DOE’s Argonne, Brookhaven, Lawrence Berkeley, Oak Ridge, Sandia and Los Alamos National Laboratories. For more information about the DOE NSRCs, please visit http://science.energy.gov/bes/suf/user-facilities/nanoscale-science-research-centers/.

Research News & Publications Office
Georgia Institute of Technology
75 Fifth Street, N.W., Suite 314
Atlanta, Georgia 30308 USA
Media Relations Contacts: John Toon (404-894-6986)(jtoon@gatech.edu) or Abby Robinson (404-385-3364)(abby@innovate.gatech.edu).

Writer: John Toon

John Toon | Newswise Science News
Further information:
http://www.gatech.edu

More articles from Materials Sciences:

nachricht From foam to bone: Plant cellulose can pave the way for healthy bone implants
19.03.2019 | University of British Columbia

nachricht Additive printing processes for flexible touchscreens: increased materials and cost efficiency
19.03.2019 | INM - Leibniz-Institut für Neue Materialien gGmbH

All articles from Materials Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: The taming of the light screw

DESY and MPSD scientists create high-order harmonics from solids with controlled polarization states, taking advantage of both crystal symmetry and attosecond electronic dynamics. The newly demonstrated technique might find intriguing applications in petahertz electronics and for spectroscopic studies of novel quantum materials.

The nonlinear process of high-order harmonic generation (HHG) in gases is one of the cornerstones of attosecond science (an attosecond is a billionth of a...

Im Focus: Magnetic micro-boats

Nano- and microtechnology are promising candidates not only for medical applications such as drug delivery but also for the creation of little robots or flexible integrated sensors. Scientists from the Max Planck Institute for Polymer Research (MPI-P) have created magnetic microparticles, with a newly developed method, that could pave the way for building micro-motors or guiding drugs in the human body to a target, like a tumor. The preparation of such structures as well as their remote-control can be regulated using magnetic fields and therefore can find application in an array of domains.

The magnetic properties of a material control how this material responds to the presence of a magnetic field. Iron oxide is the main component of rust but also...

Im Focus: Self-healing coating made of corn starch makes small scratches disappear through heat

Due to the special arrangement of its molecules, a new coating made of corn starch is able to repair small scratches by itself through heat: The cross-linking via ring-shaped molecules makes the material mobile, so that it compensates for the scratches and these disappear again.

Superficial micro-scratches on the car body or on other high-gloss surfaces are harmless, but annoying. Especially in the luxury segment such surfaces are...

Im Focus: Stellar cartography

The Potsdam Echelle Polarimetric and Spectroscopic Instrument (PEPSI) at the Large Binocular Telescope (LBT) in Arizona released its first image of the surface magnetic field of another star. In a paper in the European journal Astronomy & Astrophysics, the PEPSI team presents a Zeeman- Doppler-Image of the surface of the magnetically active star II Pegasi.

A special technique allows astronomers to resolve the surfaces of faraway stars. Those are otherwise only seen as point sources, even in the largest telescopes...

Im Focus: Heading towards a tsunami of light

Researchers at Chalmers University of Technology and the University of Gothenburg, Sweden, have proposed a way to create a completely new source of radiation. Ultra-intense light pulses consist of the motion of a single wave and can be described as a tsunami of light. The strong wave can be used to study interactions between matter and light in a unique way. Their research is now published in the scientific journal Physical Review Letters.

"This source of radiation lets us look at reality through a new angle - it is like twisting a mirror and discovering something completely different," says...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

International Modelica Conference with 330 visitors from 21 countries at OTH Regensburg

11.03.2019 | Event News

Selection Completed: 580 Young Scientists from 88 Countries at the Lindau Nobel Laureate Meeting

01.03.2019 | Event News

LightMAT 2019 – 3rd International Conference on Light Materials – Science and Technology

28.02.2019 | Event News

 
Latest News

Laser processing is a matter for the head – LZH at the Hannover Messe 2019

25.03.2019 | Trade Fair News

A Varied Menu

25.03.2019 | Life Sciences

‘Time Machine’ heralds new era

25.03.2019 | Information Technology

VideoLinks
Science & Research
Overview of more VideoLinks >>>