Seminars Archive
Adriano Filipponi
Abstract
Thursday, October 11, 2001, 11:00
Seminar Room, ground floor, Building "T"
Sincrotrone Trieste, Basovizza
Probing structure and electronic properties of Ge under extreme conditions
of high pressure and or temperature combining XAFS, Tscan and ESXD.
Adriano Filipponi
( Dipartimento di Fisica, Universita` degli studi dell`Aquila)
ABSTRACT
A wide class of substances including water, forth group semiconductors
and their oxides have been speculated to have peculiar phase diagrams in
the undercooled liquid range with a phase transition line between two liquid
polymorphs (polyamorphs) ending in a critical point.
Experimental access to this exotic phases is nowadays becoming possible
on samples composed of a large number of micrometric droplets using synchrotron
radiation [2]. Several experiments have been performed in the framework
of the HS1197 long term project at the BM29 beamline of the ESRF. The experimental
setup of BM29 [1] offers the possibility to combine x-ray absorption
spectroscopy experiments with temperature scanning techniques and energy
scanning x-ray diffraction. This latter technique has been recently enhanced
with the construction of a multi-channel detector collimator instrument,
funded through the INFM PURS008 project, and now available to the users
community at BM29. Experimental devices such as the L` Aquila-Camerino
oven and the Paris-Edinburgh press an the related techniques are available
for generating pressures up to 10 GPa and temperatures up to 2500 K. The
experiments performed so far on Germanium have accessed the undercooled
liquid range down to 300 K below the melting point and the high pressure
liquid range up to 10 GPa. Structural results indicate the existence of
structural and electronic changes with P and T, the latter also highlighted
in the edge region by means of a deconvolution procedure of the core-hole
lifetime broadening [3].
[1] A. Filipponi, M. Borowski, D. T. Bowron, S. Ansell, S. De Panfilis,
A. Di Cicco, and J. P. Itie`, Rev. Sci. Instr. 71, 2422-2432
(2000).
[2] A. Filipponi, `EXAFS for liquids.`, J. Phys.: Condensed Matter
13,
R23-R60 (2001).
[3] A. Filipponi, J. Phys. B: At. Mol. Opt. Phys. 33, 2835-2846 (2000).
