Direct hexagonal transition of amorphous (Ge<inf>2</inf>Sb<inf>2</inf>Te<inf>5</inf>)<inf>0.9</inf>Se<inf>0.1</inf> thin films

Vinod Madhavan, K. Ramesh, R. Ganesan, K. S. Sangunni

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Ge<inf>2</inf>Sb<inf>2</inf>Te<inf>5</inf> (GST) is well known for its phase change properties and applications in memory and data storage. Efforts are being made to improve its thermal stability and transition between amorphous and crystalline phases. Various elements are doped to GST to improve these properties. In this work, Se has been doped to GST to study its effect on phase change properties. Amorphous GST film crystallized in to rock salt (NaCl) type structure at 150°C and then transformed to hexagonal structure at 250°C. Interestingly, Se doped GST ((GST)<inf>0.9</inf>Se<inf>0.1</inf>) film crystallized directly into hexagonal phase and the intermediate phase of NaCl is not observed. The crystallization temperature (T<inf>c</inf>) of (GST)<inf>0.9</inf>Se<inf>0.1</inf> is around 200°C, which is 50°C higher than the T<inf>c</inf> of GST. For (GST)<inf>0.9</inf>Se<inf>0.1</inf>, the threshold switching occurs at about 4.5V which is higher than GST (3V). Band gap (E<inf>opt</inf>) values of as deposited films are calculated from Tauc plot which are 0.63eV for GST and 0.66eV for (GST)<inf>0.9</inf>Se<inf>0.1</inf>. The E<inf>opt</inf> decreases for the films annealed at higher temperatures. The increased T<inf>c</inf>, E<inf>opt</inf>, the contrast in resistance and the direct transition to hexagonal phase may improve the data readability and thermal stability in the Se doped GST film.

Original languageEnglish
Article number063505
JournalApplied Physics Letters
Issue number6
Publication statusPublished - 2 Oct 2014
Externally publishedYes


ASJC Scopus subject areas

  • Physics and Astronomy (miscellaneous)

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