Abstract
Background: Hafnium Dioxide (HfO2) represents a hopeful material for gate dielectric thin films in the field of semiconductor integrated circuits. For HfO2, several crystal structures are possible, with different properties which can be difficult to describe in detail from an experimental point of view. In this study, a detailed computational approach has been shown to present a complete analysis of four HfO2 polymorphs, outlining the intrinsic properties of each phase on the basis of atomistic displacements. Methods: Density functional theory (DFT) based methods have been used to accurately describe the chemical physical properties of the polymorphs. Corrective Hubbard (U) semi-empirical terms have been added to exchange correlation energy in order to better reproduce the excited-state properties of HfO2 polymorphs. Results: the monoclinic phase resulted in the lowest cohesive energy, while the orthorhombic showed peculiar properties due to its intrinsic ferroelectric behavior. DFT + U methods showed the different responses of the four polymorphs to an applied field, and the orthorhombic phase was the least likely to undergo point defects as oxygen vacancies. Conclusions: The obtained results give a deeper insight into the differences in excited states phenomena in relation to each specific HfO2 polymorph.
Highlights
IntroductionCurrent leakage in the Complementary Metal Oxide–Semiconductor (CMOS) is significantly large for very thin SiO2 films [1,2]
The energy cut-off has been fixed at 1200 eV and the Brillouin-zone integration has been performed over a 15 × 15 × 15 k-points grid for the m-HfO2, o-HfO2, c-HfO2, and t-HfO2 polymorphs modelled
Since more than one orthorhombic phase is known for HfO2, the choice of the specific o-phase is due to the ground state cohesive energy
Summary
Current leakage in the Complementary Metal Oxide–Semiconductor (CMOS) is significantly large for very thin SiO2 films [1,2]. This leakage represents a serious problem from the viewpoint of the reliability of advanced electronic devices and the loss of electric power of materials. In this optic, the development of next-generation CMOS devices represents a very challenging point in the scaling down of their size. Thanks to its relatively high dielectric constant, large band gap, and good thermal and chemical stabilities, Hafnium Dioxide (HfO2 ) represents one of the most promising candidates among many high-k materials [3,4]
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