Electronic structures and optical properties of HfO2–TiO2 alloys studied by first-principles GGA + U approach**Project supported by the National Natural Science Foundation of China (Grant Nos. 11672087, 11502058, and 11402252).

Abstract

The phase diagram of HfO2–TiO2 system shows that when Ti content is less than 33.0 mol%, HfO2–TiO2 system is monoclinic; when Ti content increases from 33.0 mol% to 52.0 mol%, it is orthorhombic; when Ti content reaches more than 52.0 mol%, it presents rutile phase. So, we choose the three phases of HfO2–TiO2 alloys with different Ti content values. The electronic structures and optical properties of monoclinic, orthorhombic and rutile phases of HfO2–TiO2 alloys are obtained by the first-principles generalized gradient approximation (GGA)+U approach, and the effects of Ti content and crystal structure on the electronic structures and optical properties of HfO2–TiO2 alloys are investigated. By introducing the Coulomb interactions of 5d orbitals on Hf atom (), those of 3d orbitals on Ti atom (), and those of 2p orbitals on O atom (Up) simultaneously, we can improve the calculation values of the band gaps, where , , and Up values are 8.0 eV, 7.0 eV, and 6.0 eV for both the monoclinic phase and orthorhombic phase, and 8.0 eV, 7.0 eV, and 3.5 eV for the rutile phase. The electronic structures and optical properties of the HfO2–TiO2 alloys calculated by (Up = 6.0 eV or 3.5 eV) are compared with available experimental results.