First-Principles Study of Equilibrium Properties and Electronic Structures of GeTe-Sb_2Te_3 Pseudobinary Crystalline Films

摘要

On the basis of first-principles pseudopotential total energy calculations, Ge_1Sb_2Te_4, Ge_2Sb_2Te_5, and Ge_1Sb_4Te_7 of GeTe-Sb_2Te_3 pseudobinary systems were studied. First, the most possible models for Ge_1Sb_2Te_4 were compared and investigated in detail to identify the most favorable one by examining the lattice configurations, total energy, cohesive energy, and X-ray diffraction powder curves. Then, we discussed the density of states and band structures of selected models of the GeTe-Sb_2Te_3 pseudobinary system and compared the corresponding values with each other to find similar electronic structures that are due to the similar structures with repeating units of Sb_2Te_3 and GeTe layers. Furthermore, we pointed out why Ge_2Sb_2Te_5 has the most stable structure among the three compounds by referring to a "Te-Te layer" model.