Introducing Raman Spectroscopy of Crystalline Solids in the Undergraduate Curriculum
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Introducing Raman Spectroscopy of Crystalline Solids in the Undergraduate Curriculum Bahram Roughani, David Warner, and Uma Ramabadran Department of Physics, Kettering University, Flint, MI 48504-4898
ABSTRACT We describe an experiment designed as an upper level physics laboratory that introduces students to Raman Scattering of electronic materials and research methodology. This experiment is an effective approach in demonstrating the relationship between the Raman intensity of the scattered light from crystals and symmetry dependent Raman selection rules. In our measurements we alter the angle between the crystal axis and the polarization of the incident laser beam by Si (100) sample rotation. The three dimensional plot of the intensity profile versus the theoretical model is used to distinguish differences between various crystal planes of the same electronic sample. This experiment will combine optical analysis with materials aspects of electronic materials.
INTRODUCTION Raman spectroscopy is a versatile optical measurement technique that has been widely used in research work done on vapor, liquid and solid phase materials since 1928 when the first Raman measurement was reported [1-3]. This contactless and nondestructive technique could be applied to investigate various properties of materials including structural, optical, electronic, magnetic, and thermal properties. The ease of Raman polarization analysis described here introduces undergraduates to Raman spectroscopy as a powerful materials research tool. This experiment could be used to introduce students to the application of Raman spectroscopy measurement. In addition, it enables the development of spectral intensity based on Raman selection rules, thus allowing a middle path between modern research equipment and standard student laboratories. The availability of Raman systems for undergraduate research projects has benefited in particular from the advances in light sources (lasers), spectrometers, optical detectors, and advanced data acquisition techniques in recent years [4-7]. The proper usage of Raman spectroscopy in undergraduate curriculum may impact many courses and in diverse fields of science and engineering dealing with materials characterization including physics, chemistry, materials science and engineering, biology and life sciences [1]. The experiment described here was initially developed as an independent study project dealing with materials characterization. A theoretical model based on Raman selection rules and Raman tensors for (100) Si crystal symmetry is presented and experimental results supporting the theoretical prediction is presented. The level of complexity of the experimental measurement and the theoretical background makes this experiment more appropriate for an advanced or senior level laboratory. To achieve learning outcomes for this project, we developed an
alternative and simplified approach to the Raman scattering application in research work to examine the crystallographic orientations of known (100) single crystalline
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