Synchrotronbased Infrared Spectroscopy of Solids

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Synchrotron-based Infrared Spectroscopy of Solids

• T.N. Sairam and M. Premila
• Materials Science Division, IGCAR, Kalpakkam

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Introduction

• Radiation of a given wavelength characterised by
• Brightness imp factor in FTIR Spectroscopy
• Power
• Bandwidth
• Time structure
• In the infrared region
• Etendue, ? area x solid angle

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• For Thermal sources
• brightness low, particularly
• in the far infrared region
• Also, little control over
• brightness
• As a result, very poor S/N
• When etendue factor also gets limited, as in the
  case of
• Microsampling
• High Pressure Cell, etc.,
• need for brighter source, all the more
  important.
• Solution Synchrotron Radiation Source
• Extraction of large angles for FIR,
• a limiting factor

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• Apart from bending magnets,
• Another synchrotron radiating device undulator
• However, longest wavelength does not exceed the
  near infrared.
• Edge Radiation
• result of a sudden change in the longitudinal
  velocity when the electrons enter or exit dipoles
  on a storage ring.
• Strongly collimated light in the lower energy
  range
• Easier to extract angles close to ?
• Limitation Interference causes flux roll-off

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K 0.934??
P. Roy et al (PRL 2000)
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Recent FTIR Studies using SR

• Reflectivity measurement of Josehson Plasma
  resonance in Bi2212
• (Singley et al, PRB 2004)
• CSR (Bessy-II)
• Single Xl size lt1mm
• THz-Sub-THz
• R(?) spectra show strong ? dependance below Tc
• ?ps 74 cm-1 ? ?c 21 ?m

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• Carrier dynamics in Metal Superconductors by TRS
  in the Far Infrared
• (Carr et al, PRL 2000)
• NSLS
• Photo-induced pair-breaking and recombination
• Photoexcitation ?excess quasiparticles ? relax by
  e-e and e-ph scattering ? recombination gives out
  phonons 2?.
• Observed relaxation two-component decay

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• Infrared Microspectroscopy of Semiconductors
• IR useful to probe elctronic properties as well
  as detect impurities
• As the semiconducting devices become smaller,
  their performance becomes sensitive to
  microscopic defects these defects can be
  detected through their local vibrational mode
• The smallness of the sample recommends using a
  SR based IR microspectroscopy.
• Typical parameters for Infrared Microspectroscopy
  at NSLS
• The angle of SR emission for a particular freq.
  is ??1.6 (??)-1/3, ? e- bend radius ? light
  frequency.
• ? at NSLS VUV ring 191 cm opening angle 40
  milliradians extracting 100 of the infrared
  down to 250 cm-1.

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Indus - I
Parameters of Indus-I Electron energy 450MeV Beam
current 100 mA Beam lifetime 1.8 hrs Dipole
bending field 1.5 T Critical wavelength 61 Å
(200 eV) Circumference 18.96 m Photon flux (at
?c) 7x1011 photons/s/mrad Brightness 6x1011
photons/s/mm2/mrad Bunch length 113 mm Rev
freq. 15 MHz Harmonic No. 2
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Beamlines at INDUS

• CAT Metrology / Reflectometry Beamline
• IUC Angle Integrated PES Beamline
• BARC Angle Integrated /Angle Resolved PES
  Beamline
• BARC High Resolution VUV Beamline
• BARC Photo Physics Beamline
• BARC EXAFS Beamline

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Proposal

• From the foregoing details, we see the need for
• a dedicated infrared beamline with an FTIR
  experimental station at Indus so that
  measurements in the FIR-MIR region can be carried
  out with better S/N
• The types of experiments would be
• reflectance and transmission studies
• high pressure studies and
• possibly, Timeresolved spectroscopy

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References

• G.L. Carr et al, AIP Press Conf. Proc. (1996)
  418
• G.L. Carr et al, SPIE Conf. Proc. 3153 (1997) 51
• G.L. Carr, Vib. Spec. 19 (1999) 53
• P. Roy et al, PRL 84 (2000) 483
• G.L. Carr et al, PRL 85 (2000) 3001
• P. Roy et al, NIM A 457-468 (2001) 426
• M. Abo-Bakr et al, PRL 88 (2002) 254801
• R.V. Nandedkar, Curr. Sci. 82 (2002) 291
• D. Angal-Kalinin et al, Curr. Sci. 82 (2002) 283
• E.J. Singley et al, PRB 69 (2004) 092512