2025/06/23 by Yang, Hao, Luan, Qiaotong, Zhang, Qing +5
#FOS: Physical sciences #Materials Science (cond-mat.mtrl-sci) #Statistical Mechanics (cond-mat.stat-mech)
paper · doi:10.48550/arxiv.2506.18333
Fluorite oxides such as HfO2 exhibit rich and tunable phase behavior, making them promising candidates for next generation electronic devices. A key challenge is to design amorphous HfO2-based high-k materials with both structural and performance stability. Here, using molecular dynamics simulations supported by experimental measurements, we reveal that Ba doping stimulates a polyamorphic transition in HfO2, yielding a semi-ordered amorphous (SA) phase characterized by disordered oxygens embedded within an ordered metal sublattice. We find that this phase arises from degenerate short-range symmetry breaking modes, consistent with Pauling's parsimony rule. Notably, the SA structure is thermodynamically stable and displays a wider bandgap and higher dielectric constant than conventional random-packing amorphous structure, owing to suppressed subgap states and increased Born effective charges. We further demonstrate that this structural motif generalizes to Ba-, Sr-, and Ca-doped HfO2 and ZrO2, establishing a broadly applicable strategy for designing high-performance amorphous dielectrics.