Originally based on phenomenological observations, the Janovec–Kay–Dunn (JKD) scaling law has been historically used to describe the dependence of the ferroelectric coercive fields (
Knowledge about phase transitions in doped HfO2and ZrO2‐based films is crucial for developing future ferroelectric devices. These devices should perform in ambient temperature ranges with no degradation of device performance. Here, the phase transition from the polar orthorhombic to the nonpolar tetragonal phase in thin films is of significant interest. Detailed electrical and structural characterization is performed on 10 nm mixed HfxZr1‐xO2binary oxides with different ZrO2in HfO2and small changes in oxygen content. Both dopant and oxygen content directly impact the phase transition temperature between the polar and nonpolar phase. A first‐order phase transition with thermal hysteresis is observed from the nonpolar to the polar phase with a maximum in the dielectric constant. The observed phase transition temperatures confirm trends as obtained by DFT calculations. Based on the outcome of the measurements, the classification of the ferroelectric material is discussed.
more » « less- NSF-PAR ID:
- 10370838
- Publisher / Repository:
- Wiley Blackwell (John Wiley & Sons)
- Date Published:
- Journal Name:
- Advanced Electronic Materials
- Volume:
- 8
- Issue:
- 9
- ISSN:
- 2199-160X
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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Abstract E c ) on a critical length scale of the material, wherein the film thickness (t ) is considered the length scale, andE c ∝t −2/3. Here, for the first time, a JKD‐type scaling behavior is reported in an antiferroelectric material, using the ultra‐thin films of prototypical flourite‐structure binary oxide, zirconia. In these films, a decrease in the ZrO2layer thickness from 20 nm to 5.4 nm leads to an increase in critical fields for both nonpolar‐to‐polar (E a ), and polar‐to‐nonpolar (E f ) transitions, accompanied by a decrease in the average crystallite size, and an increase in the tetragonal distortion of the non‐polarP 42/nmc ground state structure. Notably, the ‐2/3 power law as in the JKD law holds when average crystallite size (d ), measured from glancing‐incident X‐ray diffraction, is considered as the critical length scale—i .e .,E a ,E f ∝d −2/3. First principles calculations suggest that the increase of tetragonality in thinner films contributes to an increase of the energy barrier for the transition from the non‐polar tetragonal ground state to the field‐induced polar orthorhombic phase, and in turn, an increase inE a critical fields. These results suggest a de‐stabilization of the ferroelectric phase with a decreasing thickness in antiferroelectric ZrO2, which is contrary to the observations in its fluorite‐structure ferroelectric counterparts. With the recent interests in utilizing antiferroelectricity for advanced semiconductor applications, our fundamental exposition of the thickness dependence of functional responses therein can accelerate the development of miniaturized, antiferroelectric electronic memory elements for the complementary metal‐oxide‐semiconductor based high‐volume manufacturing platforms. -
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