-
Double
Subtractive Stage
- Triple
additive
- Direct
Single Spectrometer
In recent years
there has been a sharp increase in the number and form of
analyses to which Raman spectroscopy has been applied. The
introduction of small bench-top spectrometer systems has certainly
opened up the fields of study. However, on the back of the
renewed interest in the Raman technique, ever more demanding
applications have arisen.
For this reason
the next generation of Research grade instruments incorporate
much of the cutting edge technology found in the bench-top
systems, but also provide the higher performance required
for samples which prove difficult or impossible to analyse
with more routine instrumentation.
The T64000 system
is designed to provide a versatile platform for Raman analysis.
It has an integrated triple spectrometer design for unprecedented
optical stability. The instrument incorporates the proven
technology of the confocal LabRam Raman microprobe. The mechanical
coupling is rigid and stable. The optical coupling is efficient
and throughput is limited only by theoretical considerations.
High
stray light rejection
Holographic notch filter technology provides a very good solution
to laser rejection for visible wavelengths in many applications.
However, there are acknowledged limitations
to the use of these filters for work close in to the laser
line. Even with specially developed low frequency accessories(4)
with many difficult samples it is still often impossible to
obtain reliable data at 10 , 20 or 30 cm-1.
In using the double
subtractive configuration of the T64000, it is possible to
obtain spectral information very close in to the laser line.
The subtractive mode is ideal for studying such detail as
LA modes in polymer systems and crystal lattice modes.
Spectrum of a proprietary
SiGe material in which it is possible to observe spectral
bands down as low as 4 cm-1.
Ultra
high resolution
With the use of the ultra-high resolution triple additive
configuration of the T64000 triple system, it is possible
to very accurately study the position of Raman bands.
This is of particular importance for
the measurements of stress in semiconductor materials such
as GaN, SiC and diamond where stress induced shifts in the
order of 0.1 cm-1
are often studied. The high resolution also offers the level
of accuracy required for the authentication and certification
of materials for Raman standards.
Raman analysis of
stressed GaN in the solid phase. Identification of shifts
in the Raman spectral features in the order of 0.2 cm-1
are observed.
Below shows the
difference in spectral resolution between a single spectrometer
and that of the triple additive mode. It can be clearly seen
that for such applications it is necessary to acquire the
data at a high resolution not achievable with a small focal
length single spectrometer.
Single
spectrometer technology
With the final mode of operation, the direct spectrograph
entrance, the system can be used with holographic notch filter
technology and as a more conventional single spectrometer
based system. The high throughput of the large optical components
means that it is then ideal for Raman mapping and even remote
probe forms of analysis.
Raman Mapped image
of Stressed Silicon interface using Single direct path operation.
UV
Raman Spectroscopy
The T64000 has many
benefits for deep UV Raman measurements.
- The
high stray light rejection enables lower frequency Raman
bands below 100cm-1 to be observed even in the deep UV (244nm).
It can provide a complete spectral analysis not limited
in its scope or range.
- The tune-ability of the double filter stage
enables all the various deep UV frequencies to be accessed
easily, (eg. 227-290nm). Hence, optimizing resonance
enhancement for particular species of components (eg. proteins
from DNA).
- The specialized UV-Vis microscope option
is adapted to working over a broad spectral range, without
the need of optics to be removed or replaced. It preserves
the high spatial discrimination across the wavelengths.
It also offers specialized UV enhanced image viewing of
the sample, and all of the standard Raman mapping facilities.
- The
spectral resolution of the 640mm focal length, as with the
LabRAM HR system enables Raman analysis to be maintained
at a standard to high spectral resolution. The resolution
of ~1.4 cm-1/pixel far improves upon the ~4 cm-1/pixel
resolution of the small benchtop instrument found in the
UV.
Summary
The list of applications to which the T64000 can be applied
is impressive including, thin films, solid state devices,
biological chemistry and techniques such as UV, resonance
Raman, PL and laser fluorescence.
In Summary, for demanding applications
and work which requires high laser rejection, high spectral
resolution and the obvious advantages of a continuously variable
laser filter, the triple spectrometer system is an invaluable
tool. With the introduction of the latest technology from
the smaller bench-top systems it can also be applied to more
general routine analysis. The T64000 heralds a new era for
new and more versatile high grade research Raman instrumentation. |
