Photoluminescence and Raman spectroscopy are performed in backscattering geometry, directing the incident excitation light and collecting the reflected light through an objective lens of a microscope (5-100x magnification). Raman spectroscopy is a vibtrational spectroscopy that gives access to information on the nature (bond type) and structure (crystallographic phase, stress and strain) of a material. Photoluminescence can be used to determine the bandgap, defect absorption or study recombination processes in a semiconductor-type material.
The tool is a Renishaw Confocal InVia , using a 100 mW 532 nm diode laser excitation source and a Si CCD camera for detection in the visible range. In addition, it is equipped with an InGaAs camera that allows detection in the nIR range (up to 1600 nm), which makes photoluminescence of small bandgap semiconductor such as Si possible. The motorized stage also enables mapping of samples with a resolution down to ~1 µm.