Evolutionary search for new high-kdielectric materials: methodology and applications to hafnia-based oxides

Abstract

High-k dielectric materials are important as gate oxides in microelectronics and as potential dielectrics for capacitors. In order to enable computational discovery of novel high-k dielectric materials, we propose a fitness model (energy storage density) that includes the dielectric constant, bandgap, and intrinsic breakdown field. This model, used as fitness function in conjunction with first-principles calculations and global optimization evolutionary algorithm USPEX, efficiently leads to practically important results. We found a number of high-fitness structures of SiO 2 and HfO 2 , some of which correspond to known phases and some are new. The results allow us to propose characteristics (genes) common to high-fitness structures -these are the coordination polyhedra and their degree of distortion. Our variable-composition searches in the HfO 2 -SiO 2 system uncovered several high-fitness states. This hybrid algorithm opens up a new avenue of discovering novel high-k dielectrics with both fixed and variable compositions, and will speed up the process of materials discovery.

Prediction of new metastable $$\hbox {HfO}_{2}$$ HfO 2 phases: toward understanding ferro- and antiferroelectric films

“…(This problem does not relate to the predictions of Ref. [25], shown as light brown bars in Fig. 1.)…”

“…Despite the value of these earlier HfO 2 structure prediction studies [15,25], two problems are clear. The first problem is the relevance of the predicted structures from the viewpoint of structural energetics.…”

“…Indeed, the study of Ref. [25] missed structures in the relevant energy range, while the later study of Ref. [15] found only four new structures over a very broad energy range, clearly not commensurate with the actual density of structures in the energy space.…”

“…[15,25] are proper here. As Table 1 indicates, or procedure successfully finds all the experimentally confirmed phases with up to 12 atoms per cell, including the high-energy, nonfluorite-based o-II (Pnma) phase, even though the procedure has been designed to target the low-energy fluorite-based structures.…”

“…In Ref. [25] Zeng et al have used the USPEX code [26,27] to theoretically predict new phases of HfO 2 and Hf n Si m O 2n+2m that may exhibit high values of the dielectric constant. USPEX is an evolutionary algorithm for global optimization developed to have a low failure rate [26].…”