Thursday, July 25, 2013

1307.6358 (Qingfeng Zeng et al.)

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

Qingfeng Zeng, Artem R. Oganov, Andriy O. Lyakhov, Congwei Xie, Xiaodong Zhang, Jin Zhang, Qiang Zhu, Bingqing Wei, Ilya Grigorenkog
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 SiO2 and HfO2, 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 HfO2-SiO2 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.
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