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HL: Halbleiterphysik

HL 12: Poster I

HL 12.9: Poster

Montag, 8. März 2004, 16:30–19:00, Poster A

Developing design criteria for phase change alloys — •Daniel Severin, Daniel Wamwangi, Mengbo Luo, and Matthias Wuttig — I. Physikalisches Institut IA, RWTH-Aachen

Phase change materials that are based upon the reversible switching between an amorphous and a crystalline state are widely used as rewritable data storage media. This work constitutes the ongoing search to establish selection criteria for new phase change alloys. The role of the average number of s and p valence electrons in structure formation is examined for a series of chalcogenide alloys: AgInTe₂, AgSnTe₂, AgSbTe₂, AuInTe₂, AuSnTe₂ and AuSbTe₂. Our results have shown that the chalcopyrite based AgInTe₂ and AuInTe₂ alloys have low optical contrast between the amorphous and crystalline state. This also correlates with the low density change of about 2 percent. The low optical contrast renders these materials unsuitable for phase change applications. On the other hand, it has been observed that the remaining alloys show a 6 fold coordination. They also have a high density change (larger than 4 percent) and show sufficient optical contrast. A closer look at the alloys which have a metastable NaCl structure reveals that their average number of s and p valence electrons is larger than 4. This suggests, that a simple selection criterion has been found which should facilitate the identification of suitable new phase change alloys.