Manufacturers build silicon-based devices from layers of different materials. Bonds – the chemical interaction between adjacent atoms – are what give materials their distinctive characteristics.
“Essentially, a bond is the glue that holds two atoms together, and it is this glue that determines material properties, like hardness and transparency,” says Dr. Kenan Gundogdu, assistant professor of physics at NC State and co-author of the research. “Bonds are formed as materials come together.
We have influenced the assembly process of silicon crystals by applying strain during bond formation. Manufacturers know that strain makes a difference in how bonds form, but up to now there hasn’t been much understanding of how this works on the atomic level.”
Gundogdu, along with Dr. David Aspnes, Distinguished University Professor of Physics, and doctoral candidate Bilal Gokce, used optical spectroscopy along with a method of analysis pioneered by Aspnes and former graduate student Dr. Eric Adles that allowed them to examine what was happening on the atomic scale when strain was applied to a silicon crystal.
“Strain has been used to affect overall chemistry for a long time,” Aspnes says. “However, no one has previously observed differences in chemical behavior of individual bonds as a result of applying strain in one direction. Now that we can see what is actually happening, we’ll gain a much better understanding of its impact on the atomic scale, and ideally be able to put it to use.”
According to Gundogdu, “Application of even small amount of strain in one direction increases the chemical reactivity of bonds in certain direction, which in turn causes structural changes. Up to now, strain has been applied when devices are made. But by looking at the effect on the individual atomic bonds we now know that we can influence chemical reactions in a particular direction, which in principle allows us to be more selective in the manufacturing process.”
The research appears online in the Sept. 27 Proceedings of the National Academy of Sciences.
“While we are able to exert some directional control over reaction rates, there remains much that we still don’t understand,” Aspnes adds. “Continuing research will allow us to identify the relevant hidden variables, and silicon-based devices may become more efficient as a result.”
The Department of Physics is part of NC State’s College of Physical and Mathematical Sciences.
Note to editors: An abstract of paper follows.
“Measurement and control of in-plane surface chemistry during the oxidation of H-terminated (111) Si”Authors: Bilal Gokce, Eric J Adles, David E. Aspnes, and Kenan Gundogdu, NC State University
Published: Sept. 27, 2010 online in Proceedings of the National Academy of Sciences
Abstract: In-plane directional control of surface chemistry during interface formation can lead to new opportunities regarding device structures and applications. Control of this type requires techniques that can probe and hence provide feedback on the chemical reactivity of bonds not only in specific directions but also in real time. Here, we demonstrate both control and measurement of the oxidation of H-terminated (111) Si. Control is achieved by externally applying uniaxial strain, and measurement by second-harmonic generation (SHG) together with the anisotropic-bond model of nonlinear optics. In this system anisotropy results because bonds in the strain direction oxidize faster than those perpendicular to it, leading in addition to transient structural changes that can also be detected at the bond level by SHG.
Tracey Peake | EurekAlert!
Engineers develop smart material that changes stiffness when twisted or bent
15.02.2018 | Iowa State University
Breaking local symmetry: Why water freezes but silica forms a glass
14.02.2018 | Institute of Industrial Science, The University of Tokyo
Breakthrough provides a new concept of the design of molecular motors, sensors and electricity generators at nanoscale
Researchers from the Institute of Organic Chemistry and Biochemistry of the CAS (IOCB Prague), Institute of Physics of the CAS (IP CAS) and Palacký University...
For photographers and scientists, lenses are lifesavers. They reflect and refract light, making possible the imaging systems that drive discovery through the microscope and preserve history through cameras.
But today's glass-based lenses are bulky and resist miniaturization. Next-generation technologies, such as ultrathin cameras or tiny microscopes, require...
Scientists from the University of Zurich have succeeded for the first time in tracking individual stem cells and their neuronal progeny over months within the intact adult brain. This study sheds light on how new neurons are produced throughout life.
The generation of new nerve cells was once thought to taper off at the end of embryonic development. However, recent research has shown that the adult brain...
Theoretical physicists propose to use negative interference to control heat flow in quantum devices. Study published in Physical Review Letters
Quantum computer parts are sensitive and need to be cooled to very low temperatures. Their tiny size makes them particularly susceptible to a temperature...
Let’s say the armrest is broken in your vintage car. As things stand, you would need a lot of luck and persistence to find the right spare part. But in the world of Industrie 4.0 and production with batch sizes of one, you can simply scan the armrest and print it out. This is made possible by the first ever 3D scanner capable of working autonomously and in real time. The autonomous scanning system will be on display at the Hannover Messe Preview on February 6 and at the Hannover Messe proper from April 23 to 27, 2018 (Hall 6, Booth A30).
Part of the charm of vintage cars is that they stopped making them long ago, so it is special when you do see one out on the roads. If something breaks or...
15.02.2018 | Event News
13.02.2018 | Event News
12.02.2018 | Event News
16.02.2018 | Information Technology
16.02.2018 | Health and Medicine
16.02.2018 | Physics and Astronomy