Direct View at Excess Electrons in TiO2 Rutile and Anatase

作者：Setvin, Martin^*; Franchini, Cesare; Hao, Xianfeng; Schmid, Michael; Janotti, Anderson; Kaltak, Merzuk; Van de Walle, Chris G.; Kresse, Georg; Diebold, Ulrike

来源：Physical Review Letters, 2014, 113(8): 086402.

DOI：10.1103/PhysRevLett.113.086402

• OXYGEN VACANCIES
• SURFACE SCIENCE

A combination of scanning tunneling microscopy and spectroscopy and density functional theory is used to characterize excess electrons in TiO2 rutile and anatase, two prototypical materials with identical chemical composition but different crystal lattices. In rutile, excess electrons can localize at any lattice Ti atom, forming a small polaron, which can easily hop to neighboring sites. In contrast, electrons in anatase prefer a free-carrier state, and can only be trapped near oxygen vacancies or form shallow donor states bound to Nb dopants. The present study conclusively explains the differences between the two polymorphs and indicates that even small structural variations in the crystal lattice can lead to a very different behavior.

• 出版日期2014-8-18