First principles study of defects in high-k HfO2

Wide‐bandgap HfO2‐V2O5 nanowires heterostructure for visible light‐driven photocatalytic degradation

“…These energy levels, for example, consist of oxygen 2 p states and hafnium 5 d states . These experimentally determined defect levels shown in Figure match quite well with the theoretical data reported in the literature . On the other hand, the oxygen defect levels found in the pure V 2 O 5 commercial powders are 0.31 and 0.65 eV, and in V 2 O 5 NWs are 0.32 and 0.56 eV, as also shown in Figure A,B, respectively (dashed lines beneath V 2 O 5 ).…”

“…The defect level information in HfO 2 is largely missing. However, from the limited theoretical studies, this indicates the existence of V 2+ and/or O 0 defects in the HfO 2 . Similar visible light emissions have been reported previously .…”

“…These PL emissions are green light emissions as mentioned above. While the defect levels in HfO 2 have not been understood clearly, limited reports suggest the observed green light emissions (Figures , , and ) to be related to some defect levels associated with oxygen vacancies . The energy levels determined after deconvolution in the pure HfO 2 used in HfO/VO nanocomposites are 1.48, 1.76, 1.98, and 2.20 eV, and in HfO/VONW nanocomposites are 1.78, 1.80, 2.00, and 2.20 eV.…”

“…While the defect levels in HfO 2 have not been understood clearly, limited reports suggest the observed green light emissions (Figures 4, S2, and S3) to be related to some defect levels associated with oxygen vacancies. 54,61,63 The energy levels determined after deconvolution in the pure HfO 2 used in HfO/VO nanocomposites are 1.48, 1.76, 1.98, and 2.20 eV, and in HfO/VONW nanocomposites are 1.78, 1.80, 2.00, and 2.20 eV. These are schematically shown in Figure 7A,B for HfO/VO and HfO/VONW nanocomposites, respectively (dashed lines beneath HfO 2 ).…”

Intrinsic Defect Limit to the Growth of Orthorhombic HfO2 and (Hf,Zr)O2 with Strong Ferroelectricity: First‐Principles Insights

“…[36] The mechanism shows clearly that point defects play important roles in the phase formation processes when their densities are high. The properties of point defects in the m-phase of HfO 2 and ZrO 2 have been well studied using density functional theory (DFT) calculations, [37,38] and recently the defects in the ferroelectric o-phase have also been studied using DFT calculations. [39,40] However, there is obvious inconsistency in the calculated formation energies of defects in pure HfO 2 (ZrO 2 ) and Hf 0.5 Zr 0.5 O 2 alloys.…”