Browsing by Author "Martin, Lane W."
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Item Effect of fabrication processes on BaTiO3 capacitor properties(AIP Publishing, 2024) Jiang, Yizhe; Tian, Zishen; Kavle, Pravin; Pan, Hao; Martin, Lane W.; Rice Advanced Materials InstituteThere is an increasing desire to utilize complex functional electronic materials such as ferroelectrics in next-generation microelectronics. As new materials are considered or introduced in this capacity, an understanding of how we can process these materials into those devices must be developed. Here, the effect of different fabrication processes on the ferroelectric and related properties of prototypical metal oxide (SrRuO3)/ferroelectric (BaTiO3)/metal oxide (SrRuO3) heterostructures is explored. Two different types of etching processes are studied, namely, wet etching of the top SrRuO3 using a NaIO4 solution and dry etching using an Ar+-ion beam (i.e., ion milling). Polarization-electric-field hysteresis loops for capacitors produced using both methods are compared. For the ion-milling process, it is found that the Ar+ beam can introduce defects into the SrRuO3/BaTiO3/SrRuO3 devices and that the milling depth strongly influences the defect level and can induce a voltage imprint on the function. Realizing that such processing approaches may be necessary, work is performed to ameliorate the imprint of the hysteresis loops via ex situ “healing” of the process-induced defects by annealing the ferroelectric material in a barium-and-oxygen-rich environment via a chemical-vapor-deposition-style process. This work provides a pathway for the nanoscale fabrication of these candidate materials for next-generation memory and logic applications.Item Emergent chirality in a polar meron to skyrmion phase transition(Springer Nature, 2023) Shao, Yu-Tsun; Das, Sujit; Hong, Zijian; Xu, Ruijuan; Chandrika, Swathi; Gómez-Ortiz, Fernando; García-Fernández, Pablo; Chen, Long-Qing; Hwang, Harold Y.; Junquera, Javier; Martin, Lane W.; Ramesh, Ramamoorthy; Muller, David A.Polar skyrmions are predicted to emerge from the interplay of elastic, electrostatic and gradient energies, in contrast to the key role of the anti-symmetric Dzyalozhinskii-Moriya interaction in magnetic skyrmions. Here, we explore the reversible transition from a skyrmion state (topological charge of −1) to a two-dimensional, tetratic lattice of merons (with topological charge of −1/2) upon varying the temperature and elastic boundary conditions in [(PbTiO3)16/(SrTiO3)16]8 membranes. This topological phase transition is accompanied by a change in chirality, from zero-net chirality (in meronic phase) to net-handedness (in skyrmionic phase). We show how scanning electron diffraction provides a robust measure of the local polarization simultaneously with the strain state at sub-nm resolution, while also directly mapping the chirality of each skyrmion. Using this, we demonstrate strain as a crucial order parameter to drive isotropic-to-anisotropic structural transitions of chiral polar skyrmions to non-chiral merons, validated with X-ray reciprocal space mapping and phase-field simulations.Item High sound pressure piezoelectric micromachined ultrasonic transducers using sputtered potassium sodium niobate(Springer Nature, 2024) Xia, Fan; Peng, Yande; Yue, Wei; Luo, Mingze; Teng, Megan; Chen, Chun-Ming; Pala, Sedat; Yu, Xiaoyang; Ma, Yuanzheng; Acharya, Megha; Arakawa, Ryuichi; Martin, Lane W.; Lin, Liwei; Rice Advanced Materials InstituteThis work presents air-coupled piezoelectric micromachined ultrasonic transducers (pMUTs) with high sound pressure level (SPL) under low-driving voltages by utilizing sputtered potassium sodium niobate K0.34Na0.66NbO3 (KNN) films. A prototype single KNN pMUT has been tested to show a resonant frequency at 106.3 kHz under 4 Vp-p with outstanding characteristics: (1) a large vibration amplitude of 3.74 μm/V, and (2) a high acoustic root mean square (RMS) sound pressure level of 105.5 dB/V at 10 cm, which is 5–10 times higher than those of AlN-based pMUTs at a similar frequency. There are various potential sensing and actuating applications, such as fingerprint sensing, touch point, and gesture recognition. In this work, we present demonstrations in three fields: haptics, loudspeakers, and rangefinders. For haptics, an array of 15 × 15 KNN pMUTs is used as a non-contact actuator to provide a focal pressure of around 160.3 dB RMS SPL at a distance of 15 mm. This represents the highest output pressure achieved by an airborne pMUT for haptic sensation on human palms. When used as a loudspeaker, a single pMUT element with a resonant frequency close to the audible range at 22.8 kHz is characterized. It is shown to be able to generate a uniform acoustic output with an amplitude modulation scheme. In the rangefinder application, pulse-echo measurements using a single pMUT element demonstrate good transceiving results, capable of detecting objects up to 2.82 m away. As such, this new class of high-SPL and low-driving-voltage pMUTs could be further extended to other applications requiring high acoustic pressure and a small form factor.Item Interplay between Point and Extended Defects and Their Effects on Jerky Domain-Wall Motion in Ferroelectric Thin Films(American Physical Society, 2024) Bulanadi, Ralph; Cordero-Edwards, Kumara; Tückmantel, Philippe; Saremi, Sahar; Morpurgo, Giacomo; Zhang, Qi; Martin, Lane W.; Nagarajan, Valanoor; Paruch, Patrycja; Rice Advanced Materials InstituteDefects have a significant influence on the polarization and electromechanical properties of ferroelectric materials. Statistically, they can be seen as random pinning centers acting on an elastic manifold, slowing domain-wall propagation and raising the energy required to switch polarization. Here we show that the “dressing” of defects can lead to unprecedented control of domain-wall dynamics. We engineer defects of two different dimensionalities in ferroelectric oxide thin films—point defects externally induced via He2+ bombardment, and extended quasi-one-dimensional 𝑎 domains formed in response to internal strains. The 𝑎 domains act as extended strong pinning sites (as expected) imposing highly localized directional constraints. Surprisingly, the induced point defects in the He2+ bombarded samples orient and align to impose further directional pinning, screening the effect of 𝑎 domains. This defect interplay produces more uniform and predictable domain-wall dynamics. Such engineered interactions between defects are crucial for advancements in ferroelectric devices.Item Non-volatile magnon transport in a single domain multiferroic(Springer Nature, 2024) Husain, Sajid; Harris, Isaac; Meisenheimer, Peter; Mantri, Sukriti; Li, Xinyan; Ramesh, Maya; Behera, Piush; Taghinejad, Hossein; Kim, Jaegyu; Kavle, Pravin; Zhou, Shiyu; Kim, Tae Yeon; Zhang, Hongrui; Stevenson, Paul; Analytis, James G.; Schlom, Darrell; Salahuddin, Sayeef; Íñiguez-González, Jorge; Xu, Bin; Martin, Lane W.; Caretta, Lucas; Han, Yimo; Bellaiche, Laurent; Yao, Zhi; Ramesh, Ramamoorthy; Rice Advanced Materials InstituteAntiferromagnets have attracted significant attention in the field of magnonics, as promising candidates for ultralow-energy carriers for information transfer for future computing. The role of crystalline orientation distribution on magnon transport has received very little attention. In multiferroics such as BiFeO3 the coupling between antiferromagnetic and polar order imposes yet another boundary condition on spin transport. Thus, understanding the fundamentals of spin transport in such systems requires a single domain, a single crystal. We show that through Lanthanum (La) substitution, a single ferroelectric domain can be engineered with a stable, single-variant spin cycloid, controllable by an electric field. The spin transport in such a single domain displays a strong anisotropy, arising from the underlying spin cycloid lattice. Our work shows a pathway to understanding the fundamental origins of magnon transport in such a single domain multiferroic.Item Optical Control of Adaptive Nanoscale Domain Networks(Wiley, 2024) Zajac, Marc; Zhou, Tao; Yang, Tiannan; Das, Sujit; Cao, Yue; Guzelturk, Burak; Stoica, Vladimir; Cherukara, Mathew J.; Freeland, John W.; Gopalan, Venkatraman; Ramesh, Ramamoorthy; Martin, Lane W.; Chen, Long-Qing; Holt, Martin V.; Hruszkewycz, Stephan O.; Wen, Haidan; Rice Advanced Materials InstituteAdaptive networks can sense and adjust to dynamic environments to optimize their performance. Understanding their nanoscale responses to external stimuli is essential for applications in nanodevices and neuromorphic computing. However, it is challenging to image such responses on the nanoscale with crystallographic sensitivity. Here, the evolution of nanodomain networks in (PbTiO3)n/(SrTiO3)n superlattices (SLs) is directly visualized in real space as the system adapts to ultrafast repetitive optical excitations that emulate controlled neural inputs. The adaptive response allows the system to explore a wealth of metastable states that are previously inaccessible. Their reconfiguration and competition are quantitatively measured by scanning x-ray nanodiffraction as a function of the number of applied pulses, in which crystallographic characteristics are quantitatively assessed by assorted diffraction patterns using unsupervised machine-learning methods. The corresponding domain boundaries and their connectivity are drastically altered by light, holding promise for light-programable nanocircuits in analogy to neuroplasticity. Phase-field simulations elucidate that the reconfiguration of the domain networks is a result of the interplay between photocarriers and transient lattice temperature. The demonstrated optical control scheme and the uncovered nanoscopic insights open opportunities for the remote control of adaptive nanoscale domain networks.Item Size-Induced Ferroelectricity in Antiferroelectric Oxide Membranes(Wiley, 2023) Xu, Ruijuan; Crust, Kevin J.; Harbola, Varun; Arras, Rémi; Patel, Kinnary Y.; Prosandeev, Sergey; Cao, Hui; Shao, Yu-Tsun; Behera, Piush; Caretta, Lucas; Kim, Woo Jin; Khandelwal, Aarushi; Acharya, Megha; Wang, Melody M.; Liu, Yin; Barnard, Edward S.; Raja, Archana; Martin, Lane W.; Gu, X. Wendy; Zhou, Hua; Ramesh, Ramamoorthy; Muller, David A.; Bellaiche, Laurent; Hwang, Harold Y.Despite extensive studies on size effects in ferroelectrics, how structures and properties evolve in antiferroelectrics with reduced dimensions still remains elusive. Given the enormous potential of utilizing antiferroelectrics for high-energy-density storage applications, understanding their size effects will provide key information for optimizing device performances at small scales. Here, the fundamental intrinsic size dependence of antiferroelectricity in lead-free NaNbO3 membranes is investigated. Via a wide range of experimental and theoretical approaches, an intriguing antiferroelectric-to-ferroelectric transition upon reducing membrane thickness is probed. This size effect leads to a ferroelectric single-phase below 40 nm, as well as a mixed-phase state with ferroelectric and antiferroelectric orders coexisting above this critical thickness. Furthermore, it is shown that the antiferroelectric and ferroelectric orders are electrically switchable. First-principle calculations further reveal that the observed transition is driven by the structural distortion arising from the membrane surface. This work provides direct experimental evidence for intrinsic size-driven scaling in antiferroelectrics and demonstrates enormous potential of utilizing size effects to drive emergent properties in environmentally benign lead-free oxides with the membrane platform.Item Spin disorder control of topological spin texture(Springer Nature, 2024) Zhang, Hongrui; Shao, Yu-Tsun; Chen, Xiang; Zhang, Binhua; Wang, Tianye; Meng, Fanhao; Xu, Kun; Meisenheimer, Peter; Chen, Xianzhe; Huang, Xiaoxi; Behera, Piush; Husain, Sajid; Zhu, Tiancong; Pan, Hao; Jia, Yanli; Settineri, Nick; Giles-Donovan, Nathan; He, Zehao; Scholl, Andreas; N’Diaye, Alpha; Shafer, Padraic; Raja, Archana; Xu, Changsong; Martin, Lane W.; Crommie, Michael F.; Yao, Jie; Qiu, Ziqiang; Majumdar, Arun; Bellaiche, Laurent; Muller, David A.; Birgeneau, Robert J.; Ramesh, Ramamoorthy; Rice Advanced Materials InstituteStabilization of topological spin textures in layered magnets has the potential to drive the development of advanced low-dimensional spintronics devices. However, achieving reliable and flexible manipulation of the topological spin textures beyond skyrmion in a two-dimensional magnet system remains challenging. Here, we demonstrate the introduction of magnetic iron atoms between the van der Waals gap of a layered magnet, Fe3GaTe2, to modify local anisotropic magnetic interactions. Consequently, we present direct observations of the order-disorder skyrmion lattices transition. In addition, non-trivial topological solitons, such as skyrmioniums and skyrmion bags, are realized at room temperature. Our work highlights the influence of random spin control of non-trivial topological spin textures.Item Switching the spin cycloid in BiFeO3 with an electric field(Springer Nature, 2024) Meisenheimer, Peter; Moore, Guy; Zhou, Shiyu; Zhang, Hongrui; Huang, Xiaoxi; Husain, Sajid; Chen, Xianzhe; Martin, Lane W.; Persson, Kristin A.; Griffin, Sinéad; Caretta, Lucas; Stevenson, Paul; Ramesh, Ramamoorthy; Rice Advanced Materials InstituteBismuth ferrite (BiFeO3) is a multiferroic material that exhibits both ferroelectricity and canted antiferromagnetism at room temperature, making it a unique candidate in the development of electric-field controllable magnetic devices. The magnetic moments in BiFeO3 are arranged into a spin cycloid, resulting in unique magnetic properties which are tied to the ferroelectric order. Previous understanding of this coupling has relied on average, mesoscale measurements. Using nitrogen vacancy-based diamond magnetometry, we observe the magnetic spin cycloid structure of BiFeO3 in real space. This structure is magnetoelectrically coupled through symmetry to the ferroelectric polarization and this relationship is maintained through electric field switching. Through a combination of in-plane and out-of-plane electrical switching, coupled with ab initio studies, we have discovered that the epitaxy from the substrate imposes a magnetoelastic anisotropy on the spin cycloid, which establishes preferred cycloid propagation directions. The energy landscape of the cycloid is shaped by both the ferroelectric degree of freedom and strain-induced anisotropy, restricting the spin spiral propagation vector to changes to specific switching events.