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Abstract 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.
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Resolving Mechanical Properties and Morphology Evolution of Free‐Standing Ferroelectric Hf 0.5 Zr 0.5 O 2
Advances in creating polar structures in atomic‐layered hafnia‐zirconia (HfxZr1−xO2) films not only augurs extensive growth in studying ferroelectric nanoelectronics and neuromorphic devices, but also spurs opportunities for exploring novel integrated nanoelectromechanical systems (NEMS). Design and implementation of HfxZr1−xO2NEMS transducers necessitates accurate knowledge of elastic and electromechanical properties. Up to now, all experimental approaches for extraction of morphological content, elastic, and electromechanical properties of HfxZr1−xO2are based on solidly mounted structures, highly stressed films, and electroded architectures. Unlike HfxZr1−xO2layers embedded in electronics, NEMS transducers require free‐standing structures with highly contrasted mechanical boundaries and stress profiles. Here, a nanoresonator‐based approach for simultaneous extraction of Young's modulus and residual stress in free‐standing ferroelectric Hf0.5Zr0.5O2films is presented. High quality factor resonance modes of nanomechanical resonators created in predominantly orthorhombic Hf0.5Zr0.5O2films are measured using nondestructive optical transduction. Further, the evolution of morphology during creation of free‐standing Hf0.5Zr0.5O2structures is closely mapped using X‐ray diffraction measurements, clearly showing transformation of ferroelectric orthorhombic to nonpolar monoclinic phase upon stress relaxation. The extracted Young's modulus of 320.0 ± 29.4 GPa and residual stress ofσ = 577.4 ± 24.1 MPa show the closest match with theoretical calculations for orthorhombic Hf0.5Zr0.5O2.
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- Award ID(s):
- 1752206
- PAR ID:
- 10305075
- Publisher / Repository:
- Wiley Blackwell (John Wiley & Sons)
- Date Published:
- Journal Name:
- Advanced Engineering Materials
- Volume:
- 23
- Issue:
- 12
- ISSN:
- 1438-1656
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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