The coupling of polarization and oxygen vacancy migration in ferroelectric Hf0.5Zr0.5O2 thin films enables electrically controlled thermal memories above room temperature
Didac Barneo, Rafael Ramos, Hugo Romero, Victor Leboran, Noa Varela-Dominguez, Jose A. Pardo, Francisco Rivadulla, Eric Langenberg
Here we investigate epitaxial Hf0.5Zr0.5O2 ferroelectric thin films as potential candidates to be used as non-volatile electric-field-modulated thermal memories. The electric-field dependence of the thermal conductivity of metal/Hf0.5Zr0.5O2/YSZ devices is found to be hysteretic, resembling the polarization vs electric field hysteresis loops, being maximum (minimum) at large applied positive (negative) voltages from the top metallic electrode. This dynamic thermal response is compatible with the coupling between the ferroelectric polarization and the oxygen ion migration, in which the oxygen vacancies are the main phonon scattering sources and the polarization acts as an electrically active ion migration barrier that creates the hysteresis. This new mechanism enables two non-volatile thermal states: high (ON) and low (OFF) thermal conductivity, with an ON/OFF ratio of 1.6. Both the ON and OFF states exhibit high stability over time, though the switching speed is limited by ion mobility in the YSZ electrode.
Theory of Electrically Detected Magnetic Resonance of Silicon Vacancy-Related Spin Pairs in Silicon Carbide
University of Iowa（爱荷华大学）；Jet Propulsion Laboratory, California Institute of Technology（加州理工学院喷气推进实验室）；Donostia International Physics Center（圣塞巴斯蒂安国际物理中心）；Coastal Carolina University（海岸卡罗来纳大学）；The Pennsylvania State University（宾夕法尼亚州立大学）；Eindhoven University of Technology（埃因霍温理工大学）
Electrically driven emission from negatively charged silicon-vacancy, (SiV)- centres in single crystal diamond is demonstrated. The SiV centres were generated using ion implantation into an intrinsic (i) region of a p-i-n single crystal diamond diode. Both electroluminescence and the photoluminescence signals exhibit the typical emission that is attributed to the (SiV)- centres. Under forward and reversed biased PL measurements, no signal from the neutral (SiV)0 defect could be observed. The realization of electrically driven (SiV)- emission is promising for scalable nanophotonics devices empl…
Spin-dependent relaxation and recombination processes in $γ$-irradiated $n$-type Czochralski-grown silicon are studied using continuous wave (cw) and pulsed electrically detected magnetic resonance (EDMR). Two processes involving the SL1 center, the neutral excited triplet state of the oxygen-vacancy complex, are observed which can be separated by their different dynamics. One of the processes is the relaxation of the excited SL1 state to the ground state of the oxygen-vacancy complex, the other a charge transfer between $^{31}$P donors and SL1 centers forming close pairs, as indicated by elec…
Resistive switching is one of the key phenomena for applications such as nonvolatile memories or neuromorphic computing. V3O5, a compound of the vanadium oxide Magnéli series, is one of the rare materials to exhibit an insulator-metal transition (IMT) above room temperature (Tc ~ 415 K). Here we demonstrate both static dc resistive switching (RS) and fast oscillatory spiking regimes in V3O5 devices at room temperature (120 K below the phase transition temperature) by applying an electric field. We use operando optical imaging to track a reflectivity change during the RS and find that a percola…
We propose a tunneling heterostructure by replacing one of the metal electrodes in a metal/ferroelectric/metal ferroelectric tunnel junction with a heavily doped semiconductor. In this metal/ferroelectric/semiconductor tunnel diode, both the height and the width of the tunneling barrier can be electrically modulated due to the ferroelectric field effect, leading to a colossal tunneling electroresistance. This idea is implemented in Pt/BaTiO3/Nb:SrTiO3 heterostructures, in which an ON/OFF conductance ratio above 10$^4$ can be readily achieved at room temperature. The colossal tunneling electror…
We demonstrate that the spin of optically addressable point defects can be coherently driven with AC electric fields. Based on magnetic-dipole forbidden spin transitions, this scheme enables spatially confined spin control, the imaging of high-frequency electric fields, and the characterization of defect spin multiplicity. While we control defects in SiC, these methods apply to spin systems in many semiconductors, including the nitrogen-vacancy center in diamond. Electrically driven spin resonance offers a viable route towards scalable quantum control of electron spins in a dense array.
The implementation of quantum networks involving quantum memories and photonic channels without the need for cryogenics would be a major technological breakthrough. Nitrogen-vacancy centers have excellent spin properties even at room temperature, but phonon-induced broadening makes it challenging to interface these spins with photons at non-cryogenic temperatures. Inspired by recent progress in achieving ultra-high mechanical quality factors, we propose that this challenge can be overcome by spin-opto-mechanical transduction. We quantify the coherence of the interface by calculating the indist…
Spin-orbit coupling enables charge currents to give rise to spin currents and vice versa, which has applications in non-volatile magnetic memories, miniature microwave oscillators, thermoelectric converters and Terahertz devices. In the past two decades, a considerable amount of research has focused on electrical spin current generation in different types of nonmagnetic materials. However, electrical spin current generation in ferromagnetic materials has only recently been actively investigated. Due to the additional symmetry breaking by the magnetization, ferromagnetic materials generate spin…
Defects creation and annihilation is a fundamental concept in device fabrication. This report studies the optical bandgap modification in MgO by MeV Ni ion irradiation-induced defect states between valance and conduction band. Ion implantation on MgO single crystal produces substitutional defect states along with F (anionic vacancy center), $F_2$, other oxygen vacancy center and V (cationic vacancy center) centers confirmed from absorption and photoluminescence spectra that can be applied as filament in valance charge memory based resistive random access memories. The variation of optical band…
Resistance Random Access Memory (RRAMTM) device, with its electrically induced nanoscale resistive switching capacity, has been gaining considerable attention as future non-volatile memory device. Here, we propose a mechanism of switching based on oxygen vacancy migration-driven change in electronic properties of the transition metal oxide (TMO) film stimulated by set pulse voltages. We used density functional theory (DFT)-based calculations to account for the effect of oxygen vacancy and its migration on the electronic properties of HfO2 and Ta/HfO2 systems, and thereby create the entire stor…
We investigated a switchable ferroelectric diode effect and its physical mechanism in Pt/BiFeO3/SrRuO3 thin-film capacitors. Our results of electrical measurements support that, near the Pt/BiFeO3 interface of as-grown samples, a defective layer (possibly, an oxygen-vacancy-rich layer) becomes formed and disturbs carrier injection. We therefore used an electrical training process to obtain ferroelectric control of the diode polarity where, by changing the polarization direction using an external bias, we could switch the transport characteristics between forward and reverse diodes. Our system …
First-generation magnetic random access memories based on anisotropic magnetoresistance required magnetic fields for both writing and reading. Modern all-electrical read/write memories use instead non-relativistic spin-transport connecting the storing magnetic layer with a reference ferromagnet. Recent studies have focused on electrical manipulation of magnetic moments by relativistic spin-torques requiring no reference ferromagnet. Here we report the observation of a counterpart magnetoresistance effect in such a relativistic system which allows us to electrically detect the sign of the magne…
Point defects in diamond are of high interest as candidates for realizing solid state quantum bits, bioimaging agents, or ultrasensitive electric or magnetic field sensors. Various artificial diamond synthesis methods should introduce oxygen contamination in diamond, however, the incorporation of oxygen into diamond crystal and the nature of oxygen-related point defects are largely unknown. Oxygen may be potentially interesting as a source of quantum bits or it may interact with other point defects which are well established solid state qubits. Here we employ plane-wave supercell calculations …
Growth-controlled suppression of electrically active defects in CrSBr
Massachusetts Institute of Technology（麻省理工学院）；Wellesley College（韦尔斯利学院）；Bielefeld University（比勒费尔德大学）；Radboud University（拉德堡德大学）；University of Chemistry and Technology Prague（布拉格化工大学）
Although technologically challenging, the integration of ferroelectric thin films with graphene spintronics potentially allows the realization of highly efficient, electrically tuneable, non-volatile memories. Here, the atomic layer deposition (ALD) of ferroelectric Hf$_{0.5}$Zr$_{0.5}$O$_2$ (HZO) directly on graphene (Gr)/Co/heavy metal (HM) epitaxial stacks is investigated via the implementation of several nucleation methods. With an in-situ method employing an Al$_2$O$_3$ layer, the HZO demonstrates a remanent polarization (2Pr) of 19.2 $μC/cm^2$. An ex-situ, naturally oxidized sputtered Ta…
Interaction between dipoles often emerges intriguing physical phenomena, such as exchange bias in the magnetic heterostructures and magnetoelectric effect in multiferroics, which lead to advances in multifunctional heterostructures. However, the defect-dipole tends to be considered the undesired to deteriorate the electronic functionality. Here, we report deterministic switching between the ferroelectric and the pinched states by exploiting a new substrate of cubic perovskite, BaZrO$_{3}$, which boosts square-tensile-strain to BaTiO$_{3}$ and promotes four-variants in-plane spontaneous polariz…
Access Rate-Dependent Endurance Behavior of Ferroelectric Hafnium Zirconium Oxide Capacitors
NaMLab gGmbH（NaMLab有限公司）；Queen’s University Belfast（贝尔法斯特女王大学）；Technical University Dresden（德累斯顿工业大学）；Intel Foundry（英特尔代工）；University Applied Sciences, Department of Applied Sciences and Mechatronics（应用科学大学应用科学与机电工程系）
Ferroelectric materials are characterized by the presence of an electric dipole that can be reversed by application of an external electric field, a feature that is exploited in ferroelectric memories. All ferroelectrics are piezoelectric, and therefore exhibit a strong intrinsic coupling between polarization and elastic deformation - a feature widely used in piezoelectric transducers and high-displacement actuators. A less explored and exploited property is flexoelectricity, i.e. the coupling between polarization and a strain gradient. Though flexoelectricity is an old concept (it was discove…
Electrical switching of Néel order in an antiferromagnetic insulator is desirable as a basis for memory applications. Unlike electrically-driven switching of ferromagnetic order via spin-orbit torques, electrical switching of antiferromagnetic order remains poorly understood. Here we investigate the low-field magnetic properties of 30 nm thick, c-axis oriented $α$-Fe$_2$O$_3$ Hall devices using a diamond nitrogen-vacancy (NV) center scanning microscope. Using the canted moment of $α$-Fe$_2$O$_3$ as a magnetic handle on its Néel vector, we apply a saturating in-plane magnetic field to create a …
