Density functional study of the TiN/Ge2Sb2Te5 interface

We studied the epitaxial TiN(001)/Ge2Sb2Te5(001) (GST) interface of interest for applications in phase change non-volatile memories by means of density functional calculations. The cubic phase of GST of interest for the memory devices was considered. From geometry optimization we found an equilibrium distance of about 3.0?angstrom between Ti and Te, Ge and Sb atoms located directly above along the [001] direction. The interface formation energy of a large 1440-atom model is ?int?=?50?meV/angstrom 2. The surface energy of TiN(001) and GST(001) are ?S?=?81 and 10?meV/angstrom 2 resulting in an adhesion energy of ?ad?=?41?meV/angstrom 2. A good adhesion between the two materials can thus be achieved in the ideal epitaxial configuration. The presence of metal induced gap states (MIGS) is revealed by the analysis of KohnSham (KS) orbitals.