This grant provides support for the acquisition of an infrared spectroscopic ellipsometer for materials research and student training at Arizona State University. The instrument will be equipped with a cryostat attachment allowing variable temperature operation. Such capability is extremely rare: the new instrument will be the first of its kind manufactured in the United States. A spectroscopic ellipsometer measures the real and imaginary parts of a material's index of refraction as a function of wavelength. In the infrared range of the spectrum, the dominant optical excitations are phonons (vibrations), plasmons (collective electronic oscillations) in doped materials, and band-to-band electronic excitations in narrow gap semiconductors. Accordingly, the new ellipsometer will play a key role in the characterization of oxides, ferroelectric materials, and semiconductors, areas of active research at Arizona State University and of great interest to industrial partners. Spectroscopic ellipsometry has significant advantages over light transmission or reflection experiments. The latter measure a single quantity at each wavelength (the intensity of the transmitted or reflected light), whereas ellipsometry measures the change in polarization of the light reflected at a surface. Because this change is characterized by an amplitude ratio and a phase shift (related to the reflection coefficients for light polarized in the plane and perpendicular to the plane of incidence), ellipsometry is highly accurate and reproducible, even for low light levels. In addition, it requires no reference sample, is less affected by sample scattering of light, and can be used to determine absolute values for the optical constants without independent thickness measurements.
The project is expected to have a broad societal impact. One of its unique aspects will be the synergistic collaboration between ASU and industrial collaborators, who play a key role in the training of ASU personnel. Special emphasis will be placed on fostering scientific education. Funds are requested to support the operation of the instrument during the first year, and these funds will be expended primarily for the training of students. Industrial collaborators will play a key role in these activities, supervising students, providing samples, and teaching short courses on ellipsometry.
