Acquisition of a Comprehensive Multi-Wavelength Laser Raman System for Materials Education and Research

Iowa State University, Ames IA

Investigators

Abstract

This grant supports acquisition of a research grade multi-wavelength laser Raman spectrometer. The laser Raman spectrometer has two main features: (1) multiple laser wavelengths (400 to 800 nm, visible range) to complement the 1064 nm line of the FT-Raman spectrometer, and (2) microsampling. The multiple laser wavelengths is accomplished through a standard 633 nm Ne He laser. Notch filters will be used to get within 50-cm. exp. (-1) of the 413, 568, and 647 laser lines. To minimize the cost, the standard operating mode of spectrometer will be the microsampling microscope. For bulk samples, this provides the ability to spatially resolve the spectra to look for texture and variation in the sample. For microsamples, this provides the micron level resolution required. The microscope is equipped with an auto-focusing and xy-scan microscope stage that enables efficient collection of the spectra combined with the ability to perform automated xy-scanning of the surfaces of samples, greatly extending the power and flexibility of the spectrometer. Finally, a heating and freezing stage allows temperature dependent studies to be conducted from -196 to 600 degrees C. This enables examination of thermal stability of samples as well as the effect of temperature on the material structure. This laser Raman spectrometer will be heavily used in undergraduate and graduate teaching, as a core component in materials characterization courses that cover thermal and spectroscopic techniques of characterizing materials. In this way nearly every student in the MSE department will use these new instrument systems The new spectrometer will also be used for a summer NSF-REU site, where 12 undergraduate students from all over the country come to ISU to learn about semi-conducting materials and devices. Raman spectroscopy combined with microsampling capability has been shown by many researchers to be a critical analytical tool in the study of bulk, surface, and micro samples. Its power, flexibility, and non-destructive nature lend itself to wide spread use for nearly all classes of materials. Recent advances in the development of highly efficient, tunable, reliable, compact, and cost effective lasers combined with high resolution and rugged grating monochromators and solid state CCD detectors has moved the use of laser Raman spectroscopy from the realm of highly skilled spectroscopists into routine use by practicing materials scientists and engineers. Raman spectroscopy is particularly well suited for use in materials research due to minimal sample preparation, wide flexibility of sampling conditions (low and high temperatures, low and high pressure, low and high magnetic field, etc.), generally very sharp well resolved lines for solid state samples, and its non-destructive nature. Combined with a microsampling Raman microscope, Raman spectroscopy can be used extremely effectively in the careful study of surface chemistry, structure, morphology, texture, and even stress.