Overview of Raman Spectroscopy: Fundamental to Applications
157
3.4 Detectors
The earlier models of dispersive Raman spectrophotometer consist of thermoelectrically cooled photomultiplier tubes (PMTs) and photodiode array detectors (PADs)
as a detector segment. For better detection, the quality of the response curve and
the sensitivity should be high. Further, the number of channels and the reduction
in noise signal is also the important parameters for high-quality detection of the
Raman scattered photons. By the time evolution, these detectors were replaced by
charge transfer devices (CTDs) and charge injection devices (CIDs) which are more
sensitive than previous detectors. Moreover, the single-channel and multichannel
detectors are also used for Raman spectroscopy. However, these have certain advantages such as linear multichannel detections which exhibit the low signal to noise
ratio [9]. Therefore, the problem of the detector is overcome by advances in instrumentation and technology leads to extremely suitable devices for the detection of
Raman spectrograph such as charged coupled device (CCD) detector. The difference
between CTD and CCD is the processing of forming arrays. CCD act as a detector
by forming arrays of scattering light optical signals. In CTD the incoming optical
signal transforms into charge at the photo site which is integrated and transferred to
readout devices [1, 3] and the CCD detectors mostly have multichannel made up of
silica, on which the incident photon will generate the electron–hole pairs. Further,
the silica chip of the CCD detector contains the matrix of the contact point, placed
at the positive potential, where each point consisting the small area having 10
4 –10
6
electrons, ahead of the saturation capacity. The CCD detectors are used for laser
wavelengths of less than 1 μm. However, the low band-gap semiconductor (single
element) such as Germanium (Ge) or Indium–Gallium–Arsenic (InGaAs) detectors
are utilized for laser wavelengths of greater than 1 μm [3, 14–16].
4 Applications of Raman Spectroscopy
After 90 years, since its discovery, Raman spectroscopy is still an established, versatile and quasi-indispensable tool in the arsenal of scientists in the various fields across
the globe for the molecular investigation, characterizing the materials, finding the
crystallographic orientation and others. It is one of the rapid and non-destructive characterization techniques with the high spatial and spectral resolution that is applicable
at both the laboratory and industrial manufacturing scales. Over the past two decades,
it has gained broader acceptance as a mature analytical tool for the non-invasive and
rapid characterization and detection of various new molecular species and microbes.
This technique has applications in many fields such as material science, mineralogy,
surface analysis, biotechnology, food and beverages, environmental monitoring,
forensic science, diagnostics, medical and clinical chemistry, pharmaceutical, etc. As
it is not possible to list all of its applications in this chapter, we are primarily focusing
its application in the study of hydrogen bonding, material sciences (allotropes of
157
3.4 Detectors
The earlier models of dispersive Raman spectrophotometer consist of thermoelectrically cooled photomultiplier tubes (PMTs) and photodiode array detectors (PADs)
as a detector segment. For better detection, the quality of the response curve and
the sensitivity should be high. Further, the number of channels and the reduction
in noise signal is also the important parameters for high-quality detection of the
Raman scattered photons. By the time evolution, these detectors were replaced by
charge transfer devices (CTDs) and charge injection devices (CIDs) which are more
sensitive than previous detectors. Moreover, the single-channel and multichannel
detectors are also used for Raman spectroscopy. However, these have certain advantages such as linear multichannel detections which exhibit the low signal to noise
ratio [9]. Therefore, the problem of the detector is overcome by advances in instrumentation and technology leads to extremely suitable devices for the detection of
Raman spectrograph such as charged coupled device (CCD) detector. The difference
between CTD and CCD is the processing of forming arrays. CCD act as a detector
by forming arrays of scattering light optical signals. In CTD the incoming optical
signal transforms into charge at the photo site which is integrated and transferred to
readout devices [1, 3] and the CCD detectors mostly have multichannel made up of
silica, on which the incident photon will generate the electron–hole pairs. Further,
the silica chip of the CCD detector contains the matrix of the contact point, placed
at the positive potential, where each point consisting the small area having 10
4 –10
6
electrons, ahead of the saturation capacity. The CCD detectors are used for laser
wavelengths of less than 1 μm. However, the low band-gap semiconductor (single
element) such as Germanium (Ge) or Indium–Gallium–Arsenic (InGaAs) detectors
are utilized for laser wavelengths of greater than 1 μm [3, 14–16].
4 Applications of Raman Spectroscopy
After 90 years, since its discovery, Raman spectroscopy is still an established, versatile and quasi-indispensable tool in the arsenal of scientists in the various fields across
the globe for the molecular investigation, characterizing the materials, finding the
crystallographic orientation and others. It is one of the rapid and non-destructive characterization techniques with the high spatial and spectral resolution that is applicable
at both the laboratory and industrial manufacturing scales. Over the past two decades,
it has gained broader acceptance as a mature analytical tool for the non-invasive and
rapid characterization and detection of various new molecular species and microbes.
This technique has applications in many fields such as material science, mineralogy,
surface analysis, biotechnology, food and beverages, environmental monitoring,
forensic science, diagnostics, medical and clinical chemistry, pharmaceutical, etc. As
it is not possible to list all of its applications in this chapter, we are primarily focusing
its application in the study of hydrogen bonding, material sciences (allotropes of