6 - Vacancy formation in 2D and 3D oxides

Abstract

Physical and chemical properties of the materials are examined by creating point defects and imposing impurities that have a strong impact in the performance of device applications. Experimental defect identification is typically difficult and indirect, usually requiring an ingenious combination of different techniques. First-principles calculations have emerged as a powerful approach in the defect chemistry to complement experimental measurements and have become a reliable predictive tool to identify and characterize defects. In this chapter, we have reviewed theoretical models of point defects in crystalline materials that involve electronic-structure calculations based on density functional theory (DFT) methods and include approximations to the exchange-correlation functional (DFT+U and hybrid functionals). Our main goals are (1) to discuss the effect and importance of defects in two-dimensional and three-dimensional materials; (2) to present key quantities that are necessary in calculating the vacancy formation energies of acceptor and donor defects; and (3) to understand the conducting properties of semiconductor oxides through defect chemistry.