Computational discovery of two-dimensional HfO2 zoo based on evolutionary structure search†
Hafnium oxides have been widely applied in modern electronic and photonic devices as a thin film layer due to their wide electronic band gap and high dielectric constant. Here, based on a high-throughput evolutionary structure search, we explore a two-dimensional HfO2 zoo and identify six thermodynamic stable phases of the atomic thin monolayer. We confirm their mechanical and dynamical stabilities by calculating the elastic tensors and phonon dispersions as well as by carrying out ab initio molecular dynamic simulations at finite temperatures. In particular, we investigate the electronic and optical properties of those stable two-dimensional HfO2 structures. In spite of their diverse different structures, the two-dimensional HfO2 phases all have wide electronic band gaps and high dielectric constants, all indicating large capacitances due to the small thickness of the monolayer structures. Our findings demonstrate that atomic thin two-dimensional HfO2 could be a potential supercapacitor and dielectric layer for advanced nanoscale optoelectronic devices.