Macro-Raman laboratory unit is equipped with double grating U1000 Jobin Yvon monochromator (with two holographic 1800 grooves/mm gratings, whose synchronized rotation leads to the light dispersion), Ar+ and Kr+ ion lasers used as light sources, and Peltier effect cooled photomultiplier as a detector (model RCA 31034A - a system which counts photon by photon).
The U1000 double Raman spectrometer has a long 2x1 m focal length with a high precision drive mechanism. The double additive mode of the monochromator is ideally suited to very high spectral resolution (about 0.15 cm-1 at 579.1 nm - Hg line) and very high stray light rejection (10-14 at 20 cm-1 from the Rayleigh line), allowing the collection of low-frequency Raman spectra down to 2-5 cm-1. The dispersion of the monochromator is 9.2 cm-1/mm (0.243 nm/mm) for 514.5 nm, whereas its quantum efficiency is greater than 40% in the range (440–720) nm.
The laser spot is focused by the cylindrical or dichromate lens at the sample surface with a very small angle of incidence, corresponding to the quasi-backscattering geometry.
For low-temperature measurements (20-400 K) the Leybold closed cycle helium cryostat is used. This experimental set-up has an excellent stray-light rejection and allows for the measurements close to the laser line to be made.
Macro-Raman laboratory.
Detailed scheme of the Raman scattering and photoluminescence experiment.
Jobin Yvon U1000 double monochromator.
Quantum efficiency of U1000 gratings.
The spectra acquisition is controlled by LabSpec software with a choice of measurement spectral range, step and integration time in each step, by taking into account a laser wavelength.
LabSpec software: Raman spectrum of mechanically activated ZnO powder excited by 442 nm line of He-Cd laser), measured in 4 regions with different resolution.
The U1000 double monochromator may be used for simultaneous measurements of Raman and photoluminescence spectra. The photoluminescence spectra are measured with lower resolution and wider spectral range in comparison to Raman spectra. The spectral range of the instrument depends on laser wavelength, with max range of 350-850 nm.
Raman (insets) and photoluminescence spectra of Hg0.86Cd0.14Te single crystal.