Graduate student Yeliz Celik defended her doctoral thesis in November and will graduate with a doctoral degree in physics at the end of winter quarter. Her advisor is Dr. Braslavsky.

Celik’s thesis, “Experimental Investigation of the Interactions of Hyperactive Antifreeze Proteins with Ice Crystals,” reveals important findings about how antifreeze proteins (APFs) function.

AFPs are found in organisms that have to survive cold temperatures.The proteins protect these organisms by arresting the growth of ice crystals within their bodies.

The Braslavsky group was the first to use microfluidics in AFP research. With this technique, the researchers exchanged a solution around an ice crystal while maintaining fine temperature control, Celik said.

“We use these temperature-controlled microfluidic devices to study whether antifreeze proteins bind irreversibly or reversibly to ice surfaces,” she said.

The research revealed that antifreeze proteins bind irreversibly to the surface of an ice crystal. It also produced data demonstrating that AFPs can suppress ice melting.

Although the idea of superheating ice crystals in AFP solutions originated years ago, this was the first experiment to provide quantitative proof for the phenomenon.

Before joining the Braslavsky group in 2006, Celik earned her masters degree in science education from Bogazici University in Turkey. She plans to complete two years of post-doc research before teaching physics at the university level.

Celik says that having her work with AFPs published will be the most rewarding part of the research process.

Dr. Goetz is a professor of chemical and biomecular engineering and an NQPI member. For more information about his collaboration with Interthyr Corporation, read this article from the Ohio University Office of Research Communications.

Prof. Ameenah Al-Ahmadi from Umm Al-Qura University in Saudi Arabia visited Ohio University November 25 to present a lecture titled, "1D Exciton Fine Structure in Single Walled Carbon Nanotubes." Dr. Al-Ahmadi earned a doctorate and masters degree in physics from OU and  now researches  the optical properties of semiconductor colloidal quantum dots. 

Dr. Lena Ivanova visited Ohio University in November to discuss her nanoscience research with NQPI members. During her visit she also presented her research in a seminar to students and faculty members.

Her presentation, “Characterization of GaAsN Quantum Wells, GaInNAs Quantum Dots and GaN (1-100) surfaces by Scanning Tunneling Microscopy,” was based on findings from her doctoral work.

Dr. Ivanova received her diploma degree and PhD in solid state physics from the Technical University Berlin, Germany. Her research interests include compound semiconductors and low-dimensional structures.She is currently working with non-polar GaN surfaces and InN/GaN heterostructures using scanning tunneling microscopy and spectroscopy.

Dr. Art Smith and Dr. Lena Ivanova pause for a quick photo.

Kangkang Wang, Dr. Lena Ivanova, Dr.Yinghao Liu and Wenzhi Lin pose in the Smith group lab.

Graduate student Greg Petersen continued his PhD research at the National Atomic Energy Commission in Buenos Aires this summer as part of the Spin-Polarized Partnership for International Research and Education (SPIRE).

During his stay in Buenos Aires, Petersen learned a new research technique that he will incorporate into his work with Dr. Sandler—parameterized tight binding.

Petersen says explaining his research to the directors at the National Atomic Energy Commission was challenging but rewarding.

“When I went there, I had to defend how I saw the research problem,” he said. “The directors would ask me questions that would help me find holes in my understanding.”

When not researching, Petersen explored Buenos Aires and other parts of Argentina. For more on his trip, read his SPIRE blog.

• Physics alumnus Venkatraman “Venki” Ramakrishnan was recently awarded the Nobel Prize in Chemistry for his work on the function of ribosomes.

• Saw Wai-Hla and Greg VanPatten have returned from their sabbaticals. Each spent time researching in Germany.

• Alexander Govorov is currently on sabbatical.

• Savas Kaya sponsored the Friday science talks on OU’s local WOUB radio station on behalf of the Institute.

• Physics graduate student Yeliz Celik will defend her doctoral thesis in late November.

• Physics alumnus H. Lee Mosbacker is teaching a class in the OU College of Business this quarter, called Technology and Entrepreneurship (MGT 491).

• This fall NQPI will host Dr. Lena Ivanova, a post doctoral student at the Technical University in Berlin.During her visit, she will present her doctoral research on gallium nitride and quantum dot systems.

• Planning is currently underway for the 5th Annual NQPI Retreat, to be held this spring.

• Nancy Sandler and Sergio Ulloa were selected  to deliver invited talks at a recent research workshop in Israel, titled “50 Years of the Aharonov-Bohm Effect: Concepts and Applications.”

• Physics graduate student Swati Ramanathan received a $1,000 Sigma Xi Grant for her research in optical properties of nanoparticles

Michael Lorek spent his summer researching aspart of the NIST Summer Undergraduate Research Fellowship and is now pursuing a PhD at University of California Berkeley. His PhD research involves integrated circuit designs.

As an undergraduate in Dr. Savas Kaya’s group, Lorek designed ring oscillator and mixer integrated circuits using Double Gate MOSFET transistors. These novel DGMOSFETs provide more tunable electronic characteristics and could possibly extend Moore’s Law scaling due to their short channel lengths, he said.

“My research work under Dr. Kaya at OU gave me good intuition about the operation of common circuits, the operation of transistors of different types and the fabrication processes involved in making integral circuits,”he said.

This research also gave him a strong foundation for his work with CMOS circuitry at his NIST fellowship.

Models developed by Anh Tuan Ngo and Sergio Ulloa helped a University of Cincinnati researcher control spin with an electrical field.

 For decades, the transistors inside radios, televisions and other everyday items have transmitted data by controlling the movement of the electron’s charge. Scientists have now discovered that transistors could use less energy, generate less heat and operate at higher speeds if they exploited another property of the electron: its spin.

In 1921, scientists discovered that each electron has spin. Since then, researchers around the world and at Ohio University have been developing electronic devices that embed data inside an electron’s spin. The emerging field of spin electronics—or spintronics—could revolutionize memory storage devices and quantum computers.

Until now, scientists in spintronics have controlled spin by attaching an external magnet directly to the devices. But with the demand for smaller transistors on the rise, a bulky magnet is not an efficient or practical way to manipulate spin’s orientation, said Sergio Ulloa, professor of physics.

“The holy grail in spintronics is to address spin with something other than magnets,” he said. “An electrical field is portable and easy to switch on and off.”

Ulloa and graduate student Anh Tuan Ngo helped solve this issue by providing theoretical modeling for a recent experiment that was the first to successfully control  an electron’s spin using purely electrical fields. These findings were published in the article, “All-Electric Quantum Point Contact Spin-Polarizer." (Nat. Nanotechnol., 2009). 

The team collaborated with an University of Cincinnati research group led by Philippe Debray and Marc Cahay. Debray conceived and designed the experiments, while the OU researchers provided calculations explaining the behavior of the electrons in Debray’s experiment and predicted how strong the electric field’s control over the spin would be.

Asymmetry allows the electrons to recognize which direction they are traveling along the wire. This, due to relativistic effects, helps their spin determine which way is up, thus allowing the electrons to engage in spin-orbit coupling and polarization. The coupling triggers the spin and the electron-electron interaction enhances it. This enabled the scientists to control the spin current electrically.

Controlling spin electronically has major implications for the future of novel devices such as transistors, but this experiment is only the first step of many, Ulloa said. The next step would be to rework the experiment so that it could be performed at a higher, more practical temperature not requiring the use of liquid helium.

“The fundamental physics in this experiment were already known. We used our imaginations to use the fundamentals in a different way,” Debray said. “But to be able to have practical applications, the next step will be to go to a higher temperature with new materials.” 

This research is supported by the Materials World Network and a National Science Foundation PIRE grant.

Micrographs of the experimental device.  The lower left image is a 3.7 x 4 square micron blowup of the quantum point contact (QPC) region in the center. The applied voltages on the lower (LG) and upper (UG) gates result in a strongly asymmetric QPC potential depicted in the upper left inset.  The combination of lateral spin-orbit coupling in the system as well as strong electron interactions result in the 100% spin polarization in the QPC shown in the right inset.

Dr. Jadwisienczak poses in his lab. He recently received funding for a new MOKE spectrograph.

When Wojciech Jadwisienczak pulled an old magnetic characterization system out from the corner of his lab two years ago, he knew the equipment was outdated. For starters, the heart of the system—its electromagnet—was more than 40 years old.

“New equipment for magnetic characterization is badly needed at OU,” said Jadwisienczak, assistant professor of electrical engineering. “We have limited capability to characterize magnetic materials at the micro or nano scale after they are taken out of the growth chamber.”

Jadwisienczak was recently awarded a DURIP grant from the Army Research Office to develop the magneto-optical Kerr effect (MOKE) spectrograph, a modular magnetic characterization system.

Although scientists have been studying magnetism for centuries, the research field is constantly yielding new materials with optimized magnetic properties suitable for novel devices. The MOKE spectrograph will help foster magnetic ex situ research — research that focuses on the properties of materials after their growth — on campus.

The MOKE spectrograph’s most important—and most expensive—component is its electromagnet, which generates a magnetic field when a current passes through its coils. The researchers place a material that needs to be characterized into this magnetic field and probe it with polarized light, typically a laser beam. When this light reflects off the material, researchers can analyze the changes of polarization in the reflected beam and can then determine what characteristics in the material caused these changes.

Using the noninvasive light beam as a probe gives the system flexibility, allowing researchers to perform experiments in different configurations and for samples with different crystallographical orientations.  The spectrograph will be capable of performing measurements in three geometries—polar, longitudal and transversal—and in a spectral range spanning from ultraviolet to near infrared.

The equipment will also be capable of operating at low temperatures. A special nonmagnetic cryogenics system will allow researchers to investigate materials with magnetic properties barely observable at room temperature without interfering with measurements.

Currently, OU researchers who grow magnetic materials send the samples to other universities for characterization. The new equipment will help meet the demand for magnetic characterization on campus, Jadwisienczak said.

“There is a loophole at OU. Unless we have collaboration between the people growing the material and the people characterizing the material, we cannot close that loophole,” he said.

He added that any researchers working with thin films or materials with magnetic properties will find the MOKE spectrograph useful. In the future, Jadwisienczak plans to adapt the MOKE system for use with low dimensional magnetic materials such as quantum dots.

The new system, called Nano-MOKE, will open up a new avenue for the post-growth magneto-optical characterization of these materials at OU, he said.