Local Joule Heating Research Articles

Ultralow-Power Programmable 3D Vertical Phase-Change Memory with Heater-All-Around Configuration.

Recent advancements in phase-change memory (PCM) technology have predominantly stemmed from material-level designs, which have led to fast and durable device performances. However, there remains a pressing need to address the enormous energy consumption through device-level electrothermal solutions. Thus, the concept of a 3D heater-all-around (HAA) PCM fabricated along the vertical nanoscale hole of dielectric/metal/dielectric stacks is proposed. The embedded thin metallic heater completely encircles the phase-change material, so it promotes highly localized Joule heating with minimal loss. Hence, a low RESET current density of 6-8 MAcm-2 and operation energy of 150-200 pJ are achieved even for a sizable hole diameter of 300nm. Beyond the conventional 2D scaling of the bottom electrode contact, it accordingly enhances ≈80% of operational energy efficiency compared to planar PCM with an identical contact area. In addition, reliable memory operations of ≈105 cycles and the 3-bits-per-cell multilevel storage despite ultrathin (<10nm) sidewall deposition of Ge2Sb2Te5 are optimized. The proposed 3D-scaled HAA-PCM architecture holds promise as a universally applicable backbone for emerging phase-change chalcogenides toward high-density, ultralow-power computing units.

Microstructure evolution and mechanical behavior of 2024 aluminum alloy under electric pulse treatment

This study examined the effects of electric pulse treatment (EPT) on solution-treated 2024 alloy. We found that the combined effect of non-uniform stress field caused by thermal expansion and localized Joule heating promoted the formation of helical dislocations. During the subsequent aging process, these severely deformed helical dislocations formed a network configuration, which accelerated the coarsening of the S phase, and the S phase also retained a helical shape. Compared to conventional solution-treated samples, the yield strength of the EPT samples increased by 24 % with almost no loss of fracture elongation. The increase in strength is primarily due to the increase of volume fraction of rod-shaped S phase，enhancing the matrix's resistance to deformation. This study proposes a simple and rapid method to adjust dislocation configurations and aging precipitation through electric pulses, offering new insights for the industrial application of aluminum alloys to swiftly enhance mechanical properties.

Unconventional mechanical responses and mechanisms of Ti-6Al-4V sheet subjected to electrically-assisted cyclic loading-unloading: Thermal and athermal effects

For the sake of unveiling the macro-micro behaviors and underlying control mechanisms of electroplastic effect (EPE) of sheet metals during recent thriving electrically-assisted incremental forming (EAIF) processes, electrically-assisted cyclic loading-unloading tension (EACT) experiments were carried out at a current density of 14～20A/mm2 followed by forced and unforced cooling. The electro-thermo-mechanical responses and the evolution rules of dislocation configurations, fracture modes, phase composition and local orientation distribution were characterized by IR imaging, SEM, quantitative EBSD and TEM tests. Moreover, the thermal and athermal components of the electrically-induced stress drop throughout the EACT processes were decoupled and systematically analyzed via temperature control tests and isothermal correction. The results show that thermal effect of electric current possesses a great proportion of 75 % in the overall stress drop and plays a key role in elastic modulus degradation and ductility enhancement by activating pyramidal {101‾1}⟨12‾10⟩ slip systems, weakening (0001) texture and promoting dynamic recrystallization (DRX) and α→β→α′ phase transformation. While the athermal effect only operates after reaching both threshold current density and plastic strain, it increases monotonically with current density, brings about “hot spots” effect, local charge imbalance and weakened atomic bonding, and further causes intensified local strain gradient, substructure formation and DRX nucleation. The ratio of athermal stress drop first decreases and then increases significantly with loading cycle at the later stage of EACT under the combined effect of local Joule heating effect and flow localization. Additionally, the athermal effect only activates short-range solute diffusion and localized diffusional α→β phase transformation, while the combined thermal and athermal effects promote long-range solute diffusion and an increasing rate in β content of 261.8 %. The present work provides theoretical basis for optimizing the EAIF forming process and realizing extreme manufacture of light-weight thin-walled complex components.

Microstructure Evolution and Mechanical Properties of In Situ TiB2/Al–Zn–Mg–Cu Composites by Electropulsing‐Assisted Solution Treatment

The traditional solution treatment is not completely applicable for in situ TiB2/Al–Zn–Mg–Cu composite due to the influence of TiB2 particles. This study investigates the impact of the electropulsing‐assisted solution (EAS) process on the microstructure evolution and mechanical properties of TiB2/Al–Zn–Mg–Cu composites. The nonuniform microstructure evolution related to the difference in temperature and current density is supported by simulative and experimental results. EAS treatment significantly enhances the degree of supersaturation, allowing phases surrounding TiB2 particles to dissolve without extensive overburning, unlike traditional solution treatments. This improvement is attributed to the reduced thermodynamic barrier and accelerated atomic diffusion, facilitated by both localized and average Joule heating effects and enhanced thermal electron/phonon scattering. Meanwhile, grain size remains stable during the temperature rise induced by EAS treatment. Furthermore, the mechanical properties of composites increase, among which the increase in strength is mainly ascribed to solid–solution strengthening, and the increase in elongation is related to multiple factors referring to TiB2 particles fracture and interface crack between the undissolved phases and matrix. This study provides an approach to achieve an efficient dissolution of phases aggregated with particles and without widespread overburning in particle‐reinforced Al matrix composites via electropulsing techniques.

Observation of Quiet‐Time Mid‐Latitude Joule Heating and Comparisons With the TIEGCM Simulation

AbstractJoule heating is a major energy sink in the solar wind‐magnetosphere‐ionosphere system and modeling it is key to understanding the impact of space weather on the neutral atmosphere. Ion drifts and neutral wind velocities are key parameters when modeling Joule heating, however there is limited validation of the modeled ion and neutral velocities at mid‐latitudes. We use the Blackstone Super Dual Auroral Radar Network radar and the Michigan North American Thermosphere Ionosphere Observing Network Fabry‐Perot interferometer to obtain the local nightside ion and neutral velocities at ∼40° geographic latitude during the nighttime of 16 July 2014. Despite being a geomagnetically quiet period, we observe significant sub‐auroral ion flows in excess of 200 ms−1. We calculate an enhancement to the local Joule heating rate due to these ion flows and find that the neutrals impart a significant increase or decrease to the total Joule heating rate of &gt;75% depending on their direction. We compare our observations to outputs from the Thermosphere Ionosphere Electrodynamic General Circulation Model (TIEGCM). At such a low geomagnetic activity however, TIEGCM was not able to model significant sub‐auroral ion flows and any resulting Joule heating enhancements equivalent to our observations. We found that the neutral winds were the primary contributor to the Joule heating rates modeled by TIEGCM rather than the ions as suggested by our observations.

Electroplasticity mechanism of Ti2AlNb alloys under hot compression with the application of a lower electric current

In this study, a lower electric current (1.0–2.0 A/mm2) was applied during hot compression of Ti2AlNb alloys, and the mechanical response, microstructure evolution, and electroplasticity mechanism were investigated. The results showed that the maximum flow stress drop could reach 18.7 % after applying a lower electric current of 2.0 A/mm2, which confirms the existence of electroplasticity. The stress drop increased with increasing electric current density. However, the flow stresses of the samples in the isothermal compression test and those subjected to a 1.0 A/mm2 electric current compression test were similar, indicating that there is a threshold value for the electroplasticity effect on flow stress. The lower strain hardening rate caused by the electric current confirmed the electroplasticity effect, promoting the softening effect. Additionally, the lower average activation energy Q, affected by the electric current, implied the improvement of the deformability of the alloy due to the deformation mechanism of dynamic recovery (DRV), dynamic globularization, or dynamic recrystallization (DRX). The gradual reduction of dislocation density with increasing electric current density resulted in the stress drop, which can be ascribed to the directional drifting electrons colliding with dislocations, which promoted the movement of dislocations by arranging the dislocations in parallel. The local high temperature induced by the local Joule heating effect at the O lamella had a strong promoting effect on the globularization of the O lamella by producing uniform lattice distortion/local strain at the O/B2 interface. With increasing furnace temperature, the drifting electrons accelerated the transformation of LAGBs to HAGBs which promoted the appearance of dynamic recrystallization grains.

Thermal analysis of GaN HEMTs using nongray multi-speed phonon lattice Boltzmann method under Joule heating effect

Gallium Nitride (GaN) high electron mobility transistors (HEMTs) exhibit superior electrical properties for power and radio frequency applications, but performance is compromised by localized Joule heating, increasing channel temperatures. Precise thermal analysis during design is essential for optimizing device architecture and management strategies. Traditional methods like the Fourier heat diffusion equation (HDE) and the phonon lattice Boltzmann method (PLBM) with the D2Q8 scheme inadequately model phonon ballistic transport at high Knudsen numbers. This study introduces a nongray multi-speed PLBM integrated with the drift-diffusion model to analyze electro-thermal processes in GaN HEMTs. Validated through simulations of thermal conductivities in two-dimensional GaN thin films, the approach examines internal temperature rise in GaN HEMTs under different gate voltages, comparing results with HDE and gray BTE models, and emphasizing the need for non-Fourier effects in thermal analysis. It also evaluates the impact of GaN layer thickness on temperature distribution, providing a robust solution for thermal analysis in GaN HEMTs and other field-effect transistors.

Unveiling microstructural damage for leakage current degradation in SiC Schottky diode after heavy ions irradiation under 200 V

Single-event burnout and single-event leakage current (SELC) in silicon carbide (SiC) power devices induced by heavy ions severely limit their space application, and the underlying mechanism is still unclear. One fundamental problem is lack of high-resolution characterization of radiation damage in the irradiated SiC power devices, which is a crucial indicator of the related mechanism. In this Letter, high-resolution transmission electron microscopy (TEM) was used to characterize the radiation damage in the 1437.6 MeV 181Ta-irradiated SiC junction barrier Schottky diode under 200 V. The amorphous radiation damage with about 52 nm in diameter and 121 nm in length at the Schottky metal (Ti)–semiconductor (SiC) interface was observed. More importantly, in the damage site the atomic mixing of Ti, Si, and C was identified by electron energy loss spectroscopy and high-angle annular dark-field scanning TEM. It indicates that the melting of the Ti–SiC interface induced by localized Joule's heating is responsible for the amorphization and the possible formation of titanium silicide, titanium carbide, or ternary phases. The mushroom-like hillock in the Ti layer can be attributed to Rayleigh–Taylor instability, as another evidence for ever-happened localized melting near the Schottky interface. These modifications at nanoscale in turn cause localized degradation of the Schottky contact, resulting in permanent increase in leakage current. This experimental study provides very valuable clues for a thorough understanding of the SELC mechanism in SiC diodes.

Flash joining of (La0.2Nd0.2Sm0.2Gd0.2Yb0.2)2Zr2O7 high-entropy ceramic to 3YSZ

(La0.2Nd0.2Sm0.2Gd0.2Yb0.2)2Zr2O7 high-entropy ceramic (HEC) and 3 mol% yttria-stabilized zirconia were directly joined in seconds using an innovative pressure-assisted flash joining technique. An optimized shear strength of 26 ± 3 MPa was obtained at 1200 °C under uniaxial pressure of 9 MPa in 30 s. The contact resistance at the interface was found to induce intense local Joule heating, which accelerated interfacial mass transport and the joining process. However, this local heating effect also led to segregation and precipitation of the HEC near the interface, forming large La/Yb-rich rare-earth zirconate grains and intergranular pores. Increasing the pressure inhibited these issues by lowering the contact resistance, suppressing grain growth, and promoting grain sliding, rearrangement, and coalescence of grain boundaries. The proposed mechanism, based on the local heating effect, provides new insights into flash joining, highlighting the critical role of this phenomenon in triggering thermal runaway and mass transport.

Mechanical behavior and underlying mechanism of nickel-based superalloy during coupling electrical pulse and ultrasonic treatment

Coupling electric pulse and ultrasonic treatment (CEPUT) is a multi-energy field-assisted forming technology that can improve the forming efficiency of materials. The current research focused on the surface modification of materials by CEPUT, lacking the explanation of its coupling mechanism. In this study, Inconel 718 was adopted as the research object to observe the mechanical behavior and microstructure after CEPUT uniaxial tension experiment. The deformation tendency of grain under coupling multi-energy field was described by analyzing the texture evolution and dislocation morphology. The coupling mechanism of ultrasonic vibration and pulsed current was revealed in CEPUT. The experimental results revealed that there was a nonlinear relationship between the increase of flow stress softening efficiency and the increase of ultrasonic energy density and current density. This phenomenon was the macroscopic manifestation of interference between initial ultrasonic vibration and vibration after energy attenuation, which was related to dislocation slip and recrystallization under coupled multi-field. In addition, more efficient path of dislocation slip was demonstrated through the CEPUT. Among them, ultrasonic vibration caused local resistance to rise at the dislocation source and dislocation pile-up, which strengthened the local Joule heating effect; while the pulsed current reduced the activation energy required for dislocation slip near the waning points. This effectively reduced the resistance of dislocation motion near the pinning point, promoting the chance of dislocation crossing and annihilation. Meanwhile, the high temperature caused by pulsed current and local high strain caused by ultrasonic vibration were more favorable to dynamic recrystallization, and the change of grain orientation was more active. The texture strength and grain orientation of the matrix can be effectively controlled by adjusting the input power of ultrasonic vibration and pulsed current.

A spacer-based approach for localized Joule heating in membrane distillation

Membrane distillation (MD) is a versatile low-temperature separation process used for desalinating saline solutions with high salt rejection rates. Its current drawbacks include low flux and high energy demand. This study presents localized electrically induced heating using ceramic-coated metallic spacers to improve MD performance. We coated Ni-Cr spacers with MgO via electrolytic deposition and calcination, optimizing for a crack-free protective surface. Smaller wire diameter Ni-Cr exhibited superior heating. When a periodic current of 0.2 A cm−2 was applied, permeate flux increased by 15% although energy consumption only increased by 4%. Continuous supply of high-grade electrical energy added no further performance improvement as compared to periodic application. Our work highlights a spacer-based approach for localized Joule heating in MD systems without compromising membrane structure, while exploring coating systems to protect conductive spacers and optimizing schemes for electrically controlled performance.

Non-uniform microstructure evolution rules and mechanisms of Ti55 alloy with initial basket-weave structure during electrically-assisted V bending

Electrically assisted V-bending (EAVB) experiments of Ti55 alloy sheets with initial basketweave structure were carried out at effective current densities of 3–5A/mm2. The history of temperature field, microstructure patterns and mechanical properties were characterized by IR imaging, OM, EBSD and hardness tests. The results show that α lamellae continuously decrease in thickness (from 2.38 μm to 0.64 μm) with increasing current density. The microstructure patterns of the three deformation zones are significantly different due to different deformation mode and electro-thermo-mechanical routes. Due to limited plastic strain, the orientation rotation and shear fracture of the α lamellae are restricted in the neutral layer, while the ones in the inner and outer layers are refined and become more uniform at mild current density. With increasing current density, the main deformation mode of α grains in the inner layer is {1010} prismatic slip and dynamic spheroidization/recrystallization tends to occur at α lamellae with <0110>α//TD orientation. In the neural and outer layer, intense local Joule heat effect induces α→β→α′ phase transformation in “hot spots”, leading to massive growth of 3 variant needle-like α′, intensified heterogeneous micro-deformation and significant strengthening effect. The combined effects of local Joule heat, residual α phase and deformation-induced defect nucleation break the strict Burgers orientation relationship between α/α’ lamellae and β matrix during EAVB and subsequent cooling process.

Anomalous enhancing effects of electric pulse treatment on strength and ductility of TC17 linear friction welding joints

Mechanical properties of TC17 titanium alloy undergo a significant reduction after linear friction welding (LFW), of which the strength and ductility are hard to be improved simultaneously by traditional aging heat treatment (AHT), seriously limiting the application of LFW in the manufacturing of TC17 titanium alloy blisks. To this end, the present work proposes to use electric pulse treatment (EPT) to enhance the strength and ductility of TC17 LFW joints simultaneously by improving its microstructure. The results show that, in comparison to the uneven distribution of α phases in the welding zone (WZ), heat-affected zone (HAZ), and base metal (BM) zone after AHT, EPT can selectively homogenize the α phase distribution of WZ and HAZ without impacting the BM. The selective effect of EPT is reflected as the synergistic influence of the local Joule heating effect and the electron wind effect, which promotes the diffusion of β phase stabilizing element Mo and leads to a competitive precipitation of β phase and α phase in the α phase transition temperature range. The ratio of α phase to β phase in the WZ and HAZ finally approaches an equilibrium point which is similar to that of BM, leading to a uniform distribution of α phase and realizing the synergy of strength-ductility of LFW joint: the maximum strength increase observed is 12.9 %, accompanied by a corresponding elongation increase of 122 % (by AHT & EPT), and the maximum plasticity improvement is 185 %, accompanied by a corresponding strength increase of 4.3 % (by EPT for 1 h). This study provides essential insights for improving the strength and ductility of LFW TC17 titanium alloy blisks and enhancing the applications of LFW in aeroengine components.

Electropulsing-enhanced atomic diffusion and recrystallization to optimize mechanical properties of Al/Cu laminated metal composites

This work adopted the combined processing of electropulsing bonding (EPB) and electropulsing rolling (EPR) to prepare high-performance Al/Cu laminated metal composites (LMCs). The results show that electropulsing (EP) significantly accelerates the diffusion of Al and Cu atoms, thus facilitating the formation of diffusion layer. Through EP treatment, the recrystallization behavior of the Al and Cu layers is enhanced. The microstructure composed of a diffusion layer with suitable thickness and fine recrystallized grains contributes to the mechanical properties. Due to the introduction of intermetallic compounds (IMCs), the hardness and elastic modulus of Al, Cu, and diffusion layers exist large differences. The hard diffusion layer can exert a rigid deformation constraint on the ductile Al and Cu layers, and promote the interface deformation. Meanwhile, the tensile strength of as-EPRed samples increases and then decreases with the increasing EP frequency, the maximum is ∼215.2 MPa at 20 kHz. Theoretical analysis indicates that the local Joule heating and athermal effect should be the principal factors for microstructure evolution and property optimization. These results are expected to clarify the EP-related mechanism on atomic diffusion and recrystallization, which provides guidance for the fabrication of Al/Cu LMCs.

The coupling effect of particle and electric current on the grain refinement of Al–Cu–Li alloy by an improved thermo-mechanical treatment with electrically-assisted annealing

An improved thermo-mechanical treatment with electrically-assistant recrystallization annealing (EARA) was proposed for Al–Cu–Li alloy with the fine and equiaxed grains. The Al–Cu–Li alloy strips were subjected to the different overaging times, asymmetric rolling and EARA. The size and number of particles had a significant effect on the average grain size. The critical particle size for particle-stimulated nucleation (PSN) was determined. The introduction of electric current did not change the critical size, however, the efficiency of PSN triggered by coarse particles was improved by 3.6 times, compared with the conventional recrystallization annealing (CRA). By the optimized overaging time, the grains were refined and the texture was weakened. The recrystallization mechanism for the specimens containing coarse particles was the discontinuous static recrystallization (DSRX) by PSN and the continuous static recrystallization (CSRX). At the constant current density and annealing time, the critical temperature for rapid recrystallization for EARA decreased by 40 °C, compared with CRA. The results were due to the local Joule heating effect, the activation energy reduction and atomic diffusion rate increase by the athermal effect of electric current. The improved RI-ITMT with EARA would be an ideal candidate for rapid grain refinement in Al–Cu–Li alloy alloys.

Asymmetric Metal–Semiconductor–Metal Al0.24Ga0.76N UV Sensors with Surface Passivation Effect Under Local Joule Heating

Asymmetric Metal–Semiconductor–Metal Al0.24Ga0.76N UV Sensors with Surface Passivation Effect Under Local Joule Heating

Microstructural modification and mechanical improvement of ultrafine-grained Ti alloy through electron wind force: An innovative approach

This study focuses on the effect of high-density pulsed electric current (HDPEC) on the microstructure and mechanical properties of ultrafine-grained (UFG) Ti–6Al–7Nb (mass%) alloy. After the UFG Ti alloy prepared by high-pressure torsion (HPT), the samples exhibit high tensile yield strengths of 1200 MPa with total elongation of ∼20 %. Interestingly, an unusual improved elongation of ∼33 % with a yield strength of 1100 MPa was obtained in samples processed by HPT plus HDPEC. Quantitative evaluation shows that the improved ductility is attributed to the decreasing of dislocation density. The electron wind force played an important role to promote the movement of dislocation easier with the assistance of local Joule heating during HDPEC processing. It is shown that the bimodal structure with a low dislocation density leads to the high strength and high ductility. It indicated that HDPEC give an effective method to improve the ductility in UFG alloys.

Conversion from memory to threshold resistance switching behavior by modulating compliance current

The volatile and nonvolatile resistance switching (RS) characteristics can be, respectively, used for the selector and memristor, which have received much attention. Thus, it is essential to find a simple and effective method to control the specific RS behavior of NbOx materials due to the co-occurrence of memory RS and threshold RS behaviors. Here, the NbOx film with a thickness of 100 nm was prepared by magnetron sputtering at 80 °C. The tungsten steel tip/NbOx/Pt device exhibited the co-existence of memory RS and threshold RS behaviors. By properly regulating compliance current (Icc), the specified memory and threshold RS behaviors were observed: the memory RS behavior occurred with an Icc of 5 mA, the threshold RS behavior occurred with an Icc of 10 mA, and integrated one selector-one-RRAM (resistive random access memory) (1S1R) RS behavior occurred with an Icc of 50 mA. Moreover, individual RS behavior showed good performance, e.g., good stability of memory RS, good repeatability and concentrated voltage distribution of threshold RS. The memory RS behavior occurred mainly due to the formation and fracture of oxygen vacancy conductive filaments (CFs). Meanwhile, mediated by local Joule heating, thermally induced conductivity change was responsible for the threshold RS behavior. Under an Icc of 50 mA, the oxygen vacancy CFs and a thermally induced conductivity change triggered the 1S1R RS behavior, which significantly suppressed the leakage current in RRAM 3D integrated structures. This work provides an efficient and convenient method for modulating and obtaining the desired RS behavior and better understanding the conversion mechanism between them.

The Role of Vacancy Dynamics in Two‐Dimensional Memristive Devices

AbstractTwo‐dimensional layered transition metal dichalcogenides (TMDCs) are promising memristive materials for neuromorphic computing systems. Despite extensive experimental work, the underlying switching mechanisms are still not understood, impeding progress in material and device functionality. This study reveals the dominant role of defect dynamics in the switching process of 2D TMDC materials. The switching process is governed by the formation and annihilation dynamics of a local vacancy depletion zone. It explains the distinct features of the device characteristics observed experimentally, including fundamentally different device behavior previously thought to originate from multiple mechanisms. Key influence factors are identified and discussed with a fully coupled and dynamic charge transport model for electrons, holes, and ionic point defects, including image‐charge‐induced Schottky barrier lowering (SBL). Thermal effects and local Joule heating are considered by coupling the transient heat transfer equation to the electronic properties. The model is validated with hysteresis and pulse measurements for various lateral 2D MoS2‐based devices, strongly corroborating the relevance of vacancy dynamics in TMDC devices and offering a new perspective on the switching mechanisms. The insights gained from this study can be used to extend the functional behavior of 2D TMDC memristive devices in future neuromorphic computing applications.

Black Phosphorus Field-Effect Transistors with Improved Contact via Localized Joule Heating.

Two-dimensional (2D) black phosphorus (BP) is considered an ideal building block for field-effect transistors (FETs) owing to its unique structure and intriguing properties. To achieve high-performance BP-FETs, it is essential to establish a reliable and low-resistance contact between the BP and the electrodes. In this study, we employed a localized Joule heating method to improve the contact between the 2D BP and gold electrodes, resulting in enhanced BP-FET performance. Upon applying a sufficiently large source-drain voltage, the zero-bias conductance of the device increased by approximately five orders of magnitude, and the linearity of the current-voltage curves was also enhanced. This contact improvement can be attributed to the formation of gold phosphide at the interface of the BP and the gold electrodes owing to current-generated localized Joule heat. The fabricated BP-FET demonstrated a high on/off ratio of 4850 and an on-state conductance per unit channel width of 1.25 μS μm-1, significantly surpassing those of the BP-FETs without electrical annealing. These findings offer a method to achieve a low-resistance BP/metal contact for developing high-performance BP-based electronic devices.