ELFT HÍRADÓ

[Zoltan Erdelyi <zerdelyi AT dragon.klte.hu>]

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                          Debreceni Egyetem
                      Szilardtest Fizika Tanszek

                             SZEMINARIUM

                               idopont
                               -------
                 2003. szeptember 12., pentek,  11:00 ora

                               Helyszin
                               --------
                     4032 Debrecen, Egyetem ter 1.
                           Foepulet I. terem

                                Program
                                -------

   Design of Phase change media for optical and electronic applications

                           Prof. Matthias Wuttig

                   Lehrstuhl für Physik neuer Materialien (IA)
                   1. Physikalisches Institut der RWTH Aachen
                   D 52056 Aachen, Germany

At present, phase change media that can met the increasing demands of 
modern storage technology are developed in industrial and university 
labs by employing experimental optimization schemes. Here we present an 
alternate approach, which is based upon the combination of combinatorial 
techniques to produce sample libraries and ab initio calculations of the 
ground state structure and the electronic respectively optical 
properties of binary and ternary Tellurium alloys. For a large number of 
samples it could be shown that only those samples with a particular 
group of structures enable phase change recording. All materials that 
show the required optical contrast between the amorphous and crystalline 
state had cubic or near-cubic structures, while materials based upon 
tetrahedral structures showed insufficient contrast. The different 
behavior of these two groups of materials can be explained in part by 
density functional theory which has been employed to determine the 
density of states, the band structure and the total energy for different 
structures of GeTe and GeSbTe based alloys as well as ternary alloys 
containing Ag, In, Sb and Te. The calculations show a variation of 
ground state structures and bonding types with stoichiometry. 
Understanding the observed trends promises the directed optimization of 
future phase change media for optical and electronic applications. 
Future challenges for the development of ultra-fast media will be 
discussed. Our present work provides encouraging evidence that switching 
in considerably less than 10 ns is already possible and switching times 
as low as 1 ns should be within reach.

Contributions by Ralf Detemple, Daniel Wamwangi, Stefan Ziegler, Zheru 
Zhang, Henning Dieker, Meng-Bo Luo, Martina Müller and Woijiech Welnic 
are gratefully acknowledged.


Presenting author:

Prof. Dr. Matthias Wuttig
Lehrstuhl für Physik neuer Materialien (IA)
1. Physikalisches Institut der RWTH Aachen
D 52056 Aachen, Germany
Phone: 01149-241-8027155
FAX: 01149-241-8022331
E-Mail: 
wuttig AT physik.rwth-aachen.de



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