@article{schroeder_mittmann_materano_lomenzo_edgington_lee_alotaibi_west_mikolajick_kersch_et al._2022, title={Temperature-Dependent Phase Transitions in HfxZr1-xO2 Mixed Oxides: Indications of a Proper Ferroelectric Material}, ISSN={["2199-160X"]}, DOI={10.1002/aelm.202200265}, abstractNote={Knowledge about phase transitions in doped HfO2 and 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‐xO2 binary oxides with different ZrO2 in HfO2 and 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.}, journal={ADVANCED ELECTRONIC MATERIALS}, author={Schroeder, Uwe and Mittmann, Terence and Materano, Monica and Lomenzo, Patrick D. and Edgington, Patrick and Lee, Young H. and Alotaibi, Meshari and West, Anthony R. and Mikolajick, Thomas and Kersch, Alfred and et al.}, year={2022}, month={May} }
 @article{lee_broughton_hsain_song_edgington_horgan_dowden_bednar_lee_parsons_et al._2022, title={The influence of crystallographic texture on structural and electrical properties in ferroelectric Hf0.5Zr0.5O2}, volume={132}, ISSN={["1089-7550"]}, url={https://doi.org/10.1063/5.0128038}, DOI={10.1063/5.0128038}, abstractNote={Ferroelectric (Hf,Zr)O2 thin films have attracted increased interest from the ferroelectrics community and the semiconductor industry due to their ability to exhibit ferroelectricity at nanoscale dimensions. The properties and performance of the ferroelectric (Hf,Zr)O2 films generally depend on various factors such as surface energy (e.g., through grain size or thickness), defects (e.g., through dopants, oxygen vacancies, or impurities), electrodes, interface quality, and preferred crystallographic orientation (also known as crystallographic texture or simply texture) of grains and/or domains. Although some factors affecting properties and performance have been studied extensively, the effects of texture on the material properties are still not understood. Here, the influence of texture of the bottom electrode and Hf0.5Zr0.5O2 (HZO) films on properties and performance is reported. The uniqueness of this work is the use of a consistent deposition process known as Sequential, No-Atmosphere Processing (SNAP) that produces films with different preferred orientations yet minimal other differences. The results shown in this study provide both new insight on the importance of the bottom electrode texture and new fundamental processing-structure–property relationships for the HZO films.}, number={24}, journal={JOURNAL OF APPLIED PHYSICS}, author={Lee, Younghwan and Broughton, Rachel A. and Hsain, H. Alex and Song, Seung Keun and Edgington, Patrick G. and Horgan, Madison D. and Dowden, Amy and Bednar, Amanda and Lee, Dong Hyun and Parsons, Gregory N. and et al.}, year={2022}, month={Dec} }
 @article{lee_hsain_fields_jaszewski_horgan_edgington_ihlefeld_parsons_jones_2021, title={Unexpectedly large remanent polarization of Hf0.5Zr0.5O2 metal-ferroelectric-metal capacitor fabricated without breaking vacuum}, volume={118}, ISSN={["1077-3118"]}, url={https://doi.org/10.1063/5.0029532}, DOI={10.1063/5.0029532}, abstractNote={We introduce an Atomic Layer Deposition (ALD) technique referred to here as Sequential, No-Atmosphere Processing (SNAP) to fabricate ferroelectric Hf0.5Zr0.5O2 capacitors in Metal–Ferroelectric–Metal (MFM) structures. SNAP involves the ALD of each layer sequentially while maintaining the sample under vacuum process conditions without ambient exposure during the entire sequential deposition processes. We first use plasma enhanced ALD to fabricate 002-textured TiN films and study the degree of texture and quality of the film by X-ray Diffraction (XRD), Time-of-Flight Secondary Ion Mass Spectrometry (ToF-SIMS), and transmission electron microscopy. Building upon the textured TiN film, we fabricate MFM capacitors with 10-nm-thick Hf0.5Zr0.5O2 via SNAP deposition and observe an unexpectedly large remanent polarization (2Pr = 54.2 μC/cm2). We report that annealing at T <800 °C and at T = 800 °C results in different ferroelectric behaviors and phases determined by grazing incidence XRD patterns. We infer that the nonpolar tetragonal phase is dominant in films treated at T <800 °C, whereas the polar orthorhombic phase is dominant in films treated at T = 800 °C. Using ToF-SIMS and x-ray spectroscopy depth profiling on MFM capacitors, we observe an increase in the concentration of defects in the Hf0.5Zr0.5O2 layer after annealing. We believe that the absence of the native passive layer between Hf0.5Zr0.5O2 and TiN layers made via SNAP deposition is responsible for the unexpectedly large remanent polarization. In addition, we associate the 002-textured TiN as potentially playing a role in realizing the unexpectedly large remanent polarization.}, number={1}, journal={APPLIED PHYSICS LETTERS}, author={Lee, Younghwan and Hsain, H. Alex and Fields, Shelby S. and Jaszewski, Samantha T. and Horgan, Madison D. and Edgington, Patrick G. and Ihlefeld, Jon F. and Parsons, Gregory N. and Jones, Jacob L.}, year={2021}, month={Jan} }