SR a brilliant sources for solid-state researches in the IR and far-IR energy domain 

Augusto Marcelli 

°Laboratori Nazionali Frascati INFN (INFN), Via E. Fermi 40, Frascati 00044, Italy


IR spectroscopy probes rotations and vibrations of molecules, low-energy excitations of solids and many other phenomena in condensed matter physics, chemistry, biophysics and materials science. We discuss far and mid-IR spectroscopy and reflectivity measurements of metallic, semiconductor and insulator systems returning accurate information as a function of external parameters such as temperature or pressure. Reflectivity experiments were applied to investigate intrinsic point defects, a characteristic that affects properties of many solid solutions such as HgCdTe. Although limited in sensitivity far-IR reflectivity may be used for a quantitative determination of the vacancy concentration in a lattice thanks to the identification of additional vibrational modes. The same method can be used to identify in a semiconductor O or H impurities that affects crystal properties and limit applications.

Far-IR spectroscopy may be also used to investigate the pressure-driven insulator-to-metal transition, one of the most intriguing phenomena observed in colossal magnetoresistance (CMR) systems. We present high-pressure far-IR absorption measurements on LaCaMnO samples exploiting the unique characteristic of synchrotron radiation emission. The actual path followed by a system towards metallization is peculiar and volume compression affects the delicate balance among existing microscopic interactions. Far-IR spectra of manganites vs. pressure show a shielding of the phonon modes and a strong reduction of the gap, a clear behavior toward a metallic character at RT vs. pressure.

Finally, because the superconducting energy gap is an important parameter, we will show that the best method to measure the gap is the measurement of the optical reflectance in the far-IR region below the transition. We will present reflectance curves addressing a typical metallic response in the new Fe-based layered superconductors that could be attributed to the gap formation in the density of state.

Legal notice
  • Legal notice:

    Copyright (c) Pielaszek Research, all rights reserved.
    The above materials, including auxiliary resources, are subject to Publisher's copyright and the Author(s) intellectual rights. Without limiting Author(s) rights under respective Copyright Transfer Agreement, no part of the above documents may be reproduced without the express written permission of Pielaszek Research, the Publisher. Express permission from the Author(s) is required to use the above materials for academic purposes, such as lectures or scientific presentations.
    In every case, proper references including Author(s) name(s) and URL of this webpage: must be provided.


Related papers
  1. Far-infrared reflectivity as a probe of point defects in Zn- and Cd-doped HgTe
  2. Discontinuity of the phonon mode frequency temperature dependence caused by a zero-gap state in HgCdTe alloys
  3. Influence of hydrogen on hydrogenated cadmium telluride optical spectra
  4.  Far-infrared reflectivity as a probe of point defects in Zn- and Cd-doped HgTe
  5. Phonon and vibrational spectra of real crystals obtained using the synchrotron radiation
  6. Influence of hydrogen on optical spectra of hydrogenated CdTe
  7. The local crystalline structure of ZnCdTe alloys obtained by Far Infrared Synchrotron Radiation measurements
  8. Defects induced by oxygen and hydrogen in CdTe crystals

Presentation: Invited oral at E-MRS Fall Meeting 2008, Symposium J, by Augusto Marcelli
See On-line Journal of E-MRS Fall Meeting 2008

Submitted: 2008-05-07 00:08
Revised:   2009-06-07 00:48
© 1998-2022 pielaszek research, all rights reserved Powered by the Conference Engine