Highly Sensitive Raman Spectroscopy by a Position-Sensitive Photomultiplier and a Triple-Stage Spectrograph with Stigmatic Optical Correction

A Raman spectrometer with extremely high sensitivity was constructed through the use of a position-sensitive photomultiplier and a triple-stage spectrograph with stigmatic optical correction. Raman spectra of Si wafer were demonstrated with the low-level excitation intensity down to 10 nW. The longitudinal optical phonon spectrum of an individual 3-layer-thick AlAs thin film buried in GaAs was obtained for the first time. The system is useful for studying a small number of atoms and molecules of various surfaces, interfaces, and ultrathin layers.