Ferroelectric HfO2 (fe-HfO2) has garnered increasing research interest for nonvolatile memories and low-power transistors. However, many challenges are to be resolved. One of them is the depolarizing effect that is commonly attributed to the formation of fe-HfO2: electrode interface. In addition to this interface, it is not hard to find that HfO2 is rarely used in isolation but most often in combination with non-ferroelectric dielectric in real device for practical reasons. This leads to the formation of fe-HfO2: dielectric interface. Recently, counterintuitive enhancement of ferroelectricity in fe-HfO2 grown on SiO2 has been discovered experimentally, opening up a previously unknown region in design space. Yet, a deeper understanding of the role of SiO2 in enabling the enhanced ferroelectricity in fe-HfO2 still lacks. Here, we investigate the electronic structures of ten fe-HfO2: oxide dielectric interfaces. We find that while in most cases, as expected, interface formation introduces depolarizing fields in fe-HfO2, SiO2 and GeO2 stand out as two abnormal dielectrics in the sense that they surprisingly hyperpolarize fe-HfO2, in consistence with the experimental findings. We provide explanations from a chemical bonding perspective. This work suggests that the interplay between fe-HfO2 and non-ferroelectric dielectric is nontrivial and cannot be neglected toward an improved understanding of HfO2 ferroelectricity.
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