Acquisition of a Sum-Frequency Generation Spectrometer for Research and Education in Materials Science

University Of Illinois At Urbana-Champaign, Urbana IL

Investigators

Abstract

This award to the University of Illinois Urbana-Champaign is for the acquisition of a sum-frequency-generation spectrometer. The instrument will help develop a clearer picture, at the microscopic level, of surfaces and buried interfaces. This picture is difficult or impossible to obtain with conventional forms of spectroscopy, because the region of interest typically has a thickness of only one nanometer. Although their dimensions are small, the technological importance of surfaces and interfaces is extremely large. For example, the Si-H bonds that passivate the Si/SiO_2 transistor interface affect the properties of 95% of the world's integrated circuits. The SFG spectrometer will allow to determine the number of bonds at the interface, and therefore to optimize the processing of Si wafers. Surfaces are also very important in catalysis and corrosion. The SFG spectrometer will enable to acquire knowledge which will help in the search for alternative corrosion inhibitors that are less harmful to the environment. Another example is the surface of polyethylene oxide (PEO), which is used to coat prosthetic devices because it prevents the adhesion of proteins and cells. SFG spectroscopy will increase our understanding of the molecular properties responsible for the biological activity of PEO, and accelerate the design of new and better biomaterials. The spectrometer will be placed in a user facility, open to all, where graduate students will be able to receive training, use a state-of-the-art instrument in their research, and interact with experts both inside and outside of their disciplines. *** This is an award from the Instrumentation for Materials Research program to the University of Illinois Urbana-Champaign for the acquisition of an infrared-visible sum-frequency-generation spectrometer. The instrument will help develop a clearer picture, at a microscopic level, of phenomena occuring at surfaces and buried interfaces, e.g. adsorption, deposition, catalysis, corrosion, templating, and steric selection. Infrared spectroscopy is well-suited to this endeavor because it allows one to identify many of the chemical bonds which determine the properties of interfaces, e.g. the Si-H bond which passivates the Si/SiO_2 transistor interface. Sum-frequency-generation spectroscopy is particularly sensitive to the interface, even though it is often less than a nanometer thick, because the signal is generated only where the sample lacks inversion symmetry. The spectrometer will help answer scientific questions of technological importance, for example: Why is chromate so effective in preventing the corrosion of aluminum? Why do cells and proteins not adhere to the surface of prothetic devices coated with polyethylene oxide? How does adding a minute amount of benzotriazole to a plating bath drastically change the surface morphology of copper? The spectrometer will be placed in a user facility where a large number of graduate students will receive training and participate in research projects to answer questions such as those above. %%%