Raman
Raman-Spektrometer
Nicolet Almega XR
The Almega XR by Thermo Nicolet is a fully software-controlled
Raman-spectrometer suitable for the characterization of any film-sample
as well as fluids and powders. The dispersive system, that is available
at our institute, comes with two possible excitation-laser-wavelengths:
532 nm (frequency-doubled Neodymium doped Yttrium Orthvanadate diode pumped
solid state laser (Nd:YVO4 DPSS), nominal power 25 mW) and 780 nm (external
stabilized diode-laser, nominal power 40 mW). In case of the 532 nm as well
as the 780 nm laser two spectral-resolution-modes are available, 7 cm-1
and 2 cm-1. The 532 nm and 780 nm laser cover a wavenumber-interval
of 6616 to -4443 / 4090 to -710 cm-1 and 3998 to -98 / 4001 to
-98 cm-1 for the low- / high-resolution-mode, respectively. The
system features four different objectives (10x, 50x, 50x long distance und
100x), which result in spot-sizes of the laser beam on the sample surface
between 4 and 1 µm, respectively.
In case of film-samples, a complete motorized sample-stage enables the system
to take spectra from several sample positions, line-scans as well as maps
with a lateral step-size of 0.2 µm in an automated fashion. In the
context of transparent samples the additional option of moving the focus-point
in and out of the surface-plane allows for depth-profiles. In combination
with the mapping tool depth-profiling is able to provide complete 3-dimensional
information of the sample of interest.
At our institute the Almega XR is used to characterize all Raman-active
film-systems as well as nanostructures. It particular, it is a very powerful
tool in analyzing individual carbon-based nanostructures.