The origin of ferroelectricity in Hf1−xZrxO2: A computational investigation and a surface energy model
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TLDR
In this paper, the structural, thermal, and dielectric properties of the ferroelectric phase of HfO2, ZrO2 and Hf0.5O2 are investigated with carefully validated density functional computations.Abstract:
The structural, thermal, and dielectric properties of the ferroelectric phase of HfO2, ZrO2, and Hf0.5Zr0.5O2 (HZO) are investigated with carefully validated density functional computations. We find that the free bulk energy of the ferroelectric orthorhombic Pca21 phase is unfavorable compared to the monoclinic P21/c and the orthorhombic Pbca phase for all investigated stoichiometries in the Hf1−xZrxO2 system. To explain the existence of the ferroelectric phase in nanoscale thin films, we explore the Gibbs/Helmholtz free energies as a function of stress and film strain and find them unlikely to become minimal in HZO films for technological relevant conditions. To assess the contribution of surface energy to the phase stability, we parameterize a model, interpolating between existing data, and find the Helmholtz free energy of ferroelectric grains minimal for a range of size and stoichiometry. From the model, we predict undoped HfO2 to be ferroelectric for a grain size of about 4 nm and epitaxial HZO below 5 nm. Furthermore, we calculate the strength of an applied electric field necessary to cause the antiferroelectric phase transformation in ZrO2 from the P42/nmc phase as 1 MV/cm in agreement with experimental data, explaining the mechanism of field induced phase transformation.read more
Citations
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Enhanced ferroelectricity in ultrathin films grown directly on silicon.
Suraj Cheema,Daewoong Kwon,Daewoong Kwon,Nirmaan Shanker,Roberto dos Reis,Shang-Lin Hsu,Shang-Lin Hsu,Jun Xiao,Haigang Zhang,Ryan Wagner,Adhiraj Datar,Margaret McCarter,Claudy Serrao,Ajay K. Yadav,Golnaz Karbasian,Cheng-Hsiang Hsu,Ava J. Tan,Li Chen Wang,Vishal Thakare,Xiang Zhang,Apurva Mehta,Evguenia Karapetrova,Rajesh V. Chopdekar,Padraic Shafer,Elke Arenholz,Elke Arenholz,Chenming Hu,Roger Proksch,Ramamoorthy Ramesh,Jim Ciston,Sayeef Salahuddin,Sayeef Salahuddin +31 more
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Ferroelectricity in undoped hafnium oxide
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TL;DR: In this paper, the authors reported the observation of ferroelectric characteristics in undoped hafnium oxide thin films in a thickness range of 4-20nm, which were fabricated using atomic layer deposition and embedded into titanium nitride based metal-insulator-metal (MIM) capacitors for electrical evaluation.
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A rhombohedral ferroelectric phase in epitaxially strained Hf0.5Zr0.5O2 thin films.
Yingfen Wei,Pavan Nukala,Pavan Nukala,Mart Salverda,Sylvia Matzen,Hong Jian Zhao,Jamo Momand,Arnoud Everhardt,Guillaume Agnus,Graeme R. Blake,Philippe Lecoeur,Bart J. Kooi,Jorge Íñiguez,Brahim Dkhil,Beatriz Noheda +14 more
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Journal ArticleDOI
Structural Changes Underlying Field-Cycling Phenomena in Ferroelectric HfO2 Thin Films
Everett D. Grimley,Tony Schenk,Xiahan Sang,Milan Pešić,Uwe Schroeder,Thomas Mikolajick,James M. LeBeau +6 more
TL;DR: In this article, electrical and structural techniques are implemented to unveil how cyclic switching changes nanoscale film structure, which modifies the polarization hysteresis and contributes to the increase in Pr and the opening of the constricted P-V hystereis that are known to occur with wake-up.
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A comprehensive study on the structural evolution of HfO2 thin films doped with various dopants
Min Hyuk Park,Tony Schenk,Chris M. Fancher,Everett D. Grimley,Chuanzhen Zhou,Claudia Richter,James M. LeBeau,Jacob L. Jones,Thomas Mikolajick,Uwe Schroeder +9 more
TL;DR: In this article, the changes in the grazing incidence X-ray diffraction (GIXRD) patterns of HfO2 films doped with Si, Al, and Gd are systematically examined.
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