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Nanofabrication Facility
Capabilities & Equipment > Characterization Systems
Confocal Raman Microscope System
Confocal Raman Microscope.
Raman micro-spectroscopy results showing the Ge-Ge, Si-Ge and Si-Si vibrational spectrums for bulk Ge (o), bulk Si (-) and Ge Quantum-dots on Si (+). The Ge quantum dots were grown by Nathan Sustersic and Jim Kolodzey.
Raman spectrum from Tylenol™ 500mg tablet.
Raman spectroscopy is a spectroscopic technique used in condensed matter physics and chemistry to study vibrational, rotational, and other low-frequency modes in a system. It relies on inelastic scattering, or Raman scattering of monochromatic light, usually from a laser in the visible, near infrared, or near ultraviolet range. The laser light interacts with phonons or other excitations in the system, resulting in the energy of the laser photons being shifted up or down. The shift in energy gives information about the phonon modes in the system. Infrared spectroscopy yields similar, but complementary information [1]. This is due to fundamental selection rules from Quantum Mechanics. Based on the symmetry of the molecule, the infrared-active vibration and rotational modes will be Raman-inactive and vice-versa. [2]. Raman spectroscopy is most useful to investigate the structural properties of semiconductors.
Our system consists of a fiber-coupled confocal Raman microscope where the excitation is provided by a frequency-stabilized DPSS laser at 532nm that can be tuned to deliver between 1 and 40 mW at the sample. The confocal aperture can be adjusted to allow either high spatial resolution or high throughput measurements. The Raman signal is fiber-coupled to our Triple-grating spectrometer. Again, a 300, 1800 or 2400 gr/mm gratings can be selected to allow either high spectral resolution or high throughput measurements. The maximum spectral resolution achieved using this system (for a high-throughput signal) is on the order of 1 cm-1 (0.03 nm at 532 nm) and the spectral measurement range goes from 100 to 4500 cm-1.
