Epitaxial Ferroelectric Hf_0.5Zr_0.5O₂ Thin Films and Their Implementations in Memristors for Brain‐Inspired Computing

Abstract

Doped‐HfO2 thin films with ferroelectricity have attracted great attention due to their potential application in semiconductor industry as negative capacitance and resistance switching memory. Despite Hf0.5Zr0.5O2 (HZO) thin films having the most robust ferroelectric properties among all doped‐HfO2 thin films, the realization of single orthorhombic phase HZO thin films is not achieved, while the direct evidence between the structural–properties relationship of orthorhombic phase HZO and ferroelectricity is not confirmed. In this work, the growth of single orthorhombic phase HZO thin films with decent ferroelectricity and resistive switching behavior is reported. With the aid of advanced structural characterization techniques, the HZO thin film is confirmed to be in the single orthorhombic phase. Next, using scanning probe microscopy techniques and macroscopic ferroelectric measurements, the single phase HZO thin films exhibit ferroelectric properties with a remanent polarization of about 20 µC cm−2. Interestingly, the HZO thin film shows ferroelectric resistive switching with an ROFF/RON ratio of about 16 100% with excellent device performance. Furthermore, brain‐like learning behavior is also observed in the HZO thin film. These results may serve to stimulate the study of ferroelectric properties of HZO thin films and their application in the electronic industry.

Growth Window of Ferroelectric Epitaxial Hf0.5Zr0.5O2 Thin Films

“…[14][15][16][17][18][19][20] Epitaxial films are of high interest for better understanding of the properties of ferroelectric hafnia, as well as for prototyping devices with ultrathin films or having small lateral size, for which the higher homogeneity of epitaxial films respect to polycrystalline films is an advantage. In spite of the evident interest, epitaxial ferroelectric hafnia is still in a nascent state, and few groups have reported epitaxial films on YSZ, [14][15][16]21,22 oxide perovskite, 17,19,23 and Si 18,20 substrates. Up to now, the epitaxial films have been grown by pulsed laser deposition (PLD), and only the influence of thickness has been discussed.…”

Engineering Ferroelectric Hf0.5Zr0.5O2 Thin Films by Epitaxial Stress

“…10 The resulting films are polycrystalline and contain paraelectric tetragonal and monoclinic phases besides the ferroelectric orthorhombic phase. 1,2,[11][12] The ferroelectric phase has been also grown epitaxially on a few substrates, including yttria-stabilized zirconia, [13][14][15][16] LaAlO3, 17 SrTiO3, [18][19][20][21] and buffered Si. 22 The research on epitaxial stabilization is just emerging in comparison with that on polycrystalline doped HfO2 films.…”

Reproducible Ultrathin Ferroelectric Domain Switching for High‐Performance Neuromorphic Computing

“…The minor conductance variation facilitates a reduction of the writing noise during the training process . In addition to the conductance variation between cycles, the linearity of the weight update in the long‐term potentiation and depression processes can also significantly affect the accuracy of the training process.…”