R&D: Five Articles on Memories Technologies

R&D: Tunable magnetic properties in compositionally graded L1₀-FePt thin films
Results establish chemical grading as a powerful design strategy to modulate anisotropy, coercivity and domain behavior in L1₀-FePt, unlocking new opportunities for materials tailored for advanced spintronic and data storage applications.

Journal of Physics D: Applied Physics has published an article written by Isaak G Vasileiadis, Dimitrios Karfaridis, Nikolaos Maniotis, Department of Physics, Aristotle University of Thessaloniki, 54124 Thessaloniki, Greece, Kristina Ignatova, Unnar B Arnalds, Science Institute, University of Iceland, Dunhaga 3, Reykjavik 107, Iceland, George Vourlias, George P Dimitrakopulos, Department of Physics, Aristotle University of Thessaloniki, 54124 Thessaloniki, Greece, Evangelos Th Papaioannou, Department of Physics, Aristotle University of Thessaloniki, 54124 Thessaloniki, Greece, and Institut für Physik, Martin-Luther-Universität Halle Wittenberg, Von-Danckelmann-Platz 3, 06120 Halle, Germany, and Thomas Kehagias, Department of Physics, Aristotle University of Thessaloniki, 54124 Thessaloniki, Greece.

Abstract: “The tetragonally ordered L1₀-FePt alloy exhibits strong magnetocrystalline anisotropy and high coercivity values, making it a model platform for high-density data storage and magnetic nanoparticles applications. However, the tunability of its magnetic properties through structural and compositional design remains a challenge. Here, we present a novel approach of fabricating compositionally graded L1₀-FePt thin films via thermally activated solid-state reactions of Fe/Pt bilayers grown on MgO(001). Upon annealing, vacancy-mediated migration and grain boundary diffusion drive the transformation into a structurally coherent columnar grain structure, consisting of epitaxial domains and misoriented regions. Nanoscale compositional analysis reveals a Pt concentration gradient, with near-stoichiometric L1₀-FePt in the upper film and a progressively Fe-rich profile near the FePt/MgO interface, while maintaining chemical ordering and tetragonality. This self-organized gradient has profound consequences, as the Fe-enriched interfacial region enhances Fe–Fe exchange stiffness, suppressing out-of-plane anisotropy and coercivity while promoting in-plane magnetization at room temperature. Magnetization reversal occurs through softened hysteresis and complex domain configurations, as confirmed by micromagnetic simulations. These results establish chemical grading as a powerful design strategy to modulate anisotropy, coercivity and domain behavior in L1₀-FePt, unlocking new opportunities for materials tailored for advanced spintronic and data storage applications.“

R&D: Interfacial Al₂O₃ effects on Hf_0.1Zr_0.9O₂ and the compact current-partitioning model in ferroelectric tunneling junctions
Resulting FTJ exhibits stable room-temperature retention over 104s for Non-volatile memory (NVM) applications.

Semiconductor Science and Technology has published an article written by Jer-Fu Wang, Graduate Institute of Electronics Engineering, National Taiwan University, No. 1, Sec. 4, Roosevelt Rd., Taipei 10617, Taiwan (R.O.C.), Taipei, Taiwan, 10617, Taiwan, Yii-Tay Chang, Program for Semiconductor Devices, Materials, and Hetero-integration (DMHI), Graduate School of Advanced Technology (GSAT), National Taiwan University, 3F,No.130,Sec. 3, Keelung Rd.,Taipei 106, Taipei, Taipei City, Taiwan, 10617, Taiwan, Yun-Wen Chen, Graduate Institute of Electronics Engineering, Department of Electrical Engineering, National Taiwan University, No. 1, Sec. 4, Roosevelt Rd., Taipei 106319, Taiwan (R.O.C.), Taipei, Taipei, Taiwan, 106319, Taiwan, Hung-Li Chiang, Chih-Hung Nien, Kuo-Yu Hsiang, Tzu-Chiang Chen, Taiwan Semiconductor Manufacturing Co Ltd, 8, Li-Hsin Rd. 6, Hsinchu Science Park, Hsinchu 300-096, Taiwan, R.O.C., Hsinchu, Taiwan Province, 300096, Taiwan, Chih-Sheng Chang, TSMC Ltd, 168, Kehuan Rd., Hsinchu Science Park, Hsinchu, Hsinchu, 308, Taiwan, C. W. Liu, Graduate Institute of Electronics Engineering, National Taiwan University, No. 1, Sec. 4, Roosevelt Rd., Taipei 106319, Taiwan (R.O.C.), Taipei, Taipei, Taiwan, 10617, Taiwan, and Min-Hung Lee, Program for Semiconductor Devices, Materials, and Hetero-integration (DMHI), Graduate School of Advanced Technology (GSAT), National Taiwan University, Room 112, MK Innovation Hall, No.1, Sec. 4, Roosevelt Rd., Taipei, Taipei, Taiwan, 106319, Taiwan.

Abstract: “In this work, we built a compact model to analyze the experimental total current for Ferroelectric Tunneling Junctions (FTJs) with bandgap engineering. Based on our model, a interfacial layer (IL) design was proposed for Hf0.1Zr0.9O2 FTJs to achieve non-volatile characteristics and an excellent on-off ratio (~100). With the current mechanism partition, the impacts from the ferroelectric current and the tunneling current are quantitatively analyzed and considered in the design for the film stack. The on-off ratio benefited from bandgap engineering can be well explained. We also found out the non-volatility can be achieved in Hf0.1Zr0.9O2 FTJs. Though Hf0.1Zr0.9O2 are typically antiferroelectric, the non-zero remanent polarization (Pr) at 0V was observed in the P-V loop of the proposed FTJ. The higher orthorhombic phase induced by the inserted Al2O3 IL was validated by physical analyses. The resulting FTJ exhibits stable room-temperature retention over 104s for Non-volatile memory (NVM) applications.“

R&D: Enhancing non-volatile memory and neuromorphic computing: integration of PRAM and OTS for scalable, energy-efficient architectures
Paper investigates integration of phase-change random access memory (PRAM) and ovonic threshold switch (OTS) devices, emphasizing their ability to advance non-volatile memory technologies, neuromorphic computing architectures, and energy-efficient systems.

Journal of Physics D: Applied Physics has published an article written by Seoyoung Park, Division of Electronics and Electrical Engineering, Dongguk University, Seoul 04620, Republic of Korea, Minsuk Koo, Department of AI Semiconductor, School of Advanced Cross-Disciplinary Studies, University of Seoul, Seoul 02504, Republic of Korea, and Sungjun Kim, Division of Electronics and Electrical Engineering, Dongguk University, Seoul 04620, Republic of Korea.

Abstract: “This paper investigates the integration of phase-change random access memory (PRAM) and ovonic threshold switch (OTS) devices, emphasizing their ability to advance non-volatile memory technologies, neuromorphic computing architectures, and energy-efficient systems. OTS devices’ nonlinear threshold switching effectively mitigates sneak currents in high-density crossbar arrays, while challenges like resistivity drift and structural relaxation are addressed through advanced modeling and experimental analysis. The study highlights innovations in phase-change materials, such as doped Sb₂Te₃ alloys and Sb₂Te₃–GeTe superlattices deposited by magnetron sputtering, which have been reported to improve thermal stability, reduce RESET power, and enhance cycling endurance compared with conventional GST-based phase-change memory devices. PRAM-OTS hybrid systems demonstrate exceptional performance in spiking and multi-layer neural networks, replicating neuronal behaviors such as integrate-and-fire dynamics and spike-timing-dependent plasticity for low-latency, energy-efficient processing in artificial intelligence, robotics, and internet of things applications. These scalable and reliable systems provide a robust framework for next-generation high-performance computational platforms, addressing key challenges in scalability, energy efficiency, and operational longevity.“

R&D: Enhancing device performance through shape design in channel-less SOT-MRAM
Authors present an experimental study on magnetic tunnel junctions (MTJs) patterned into elliptical shape and integrated within a channel-less (CHL) spin-orbit-torque magnetic random access memory (SOT-MRAM) device architecture.

Journal of Physics D: Applied Physics has published an article written by Wenlong Yang, Kaiyuan Zhou, Qingxiu Li, Hengan Zhou, Zhenghui Ji, Yang Gao, Guoxiu Qiu, Yifan Xi, Lei Zhao, Shasha Wang, Enlong Liu and Shikun He, Zhejiang Hikstor Technology Company Ltd, Hangzhou 311300, Zhejiang, People’s Republic of China.

Abstract: “We present an experimental study on magnetic tunnel junctions (MTJs) patterned into elliptical shape and integrated within a channel-less (CHL) spin-orbit-torque magnetic random access memory (SOT-MRAM) device architecture. The CHL architecture eliminates the need to stop etching at the SOT track layer, simplifying fabrication and enabling reliable large-scale manufacturing on 300 mm wafers with yield above 99.6%. The elliptical MTJ geometry enables a significant reduction in critical switching current, achieving reliable operation with a switching current of 460 μA under a 5 ns pulse. The devices exhibit a tunneling magnetoresistance ratio of up to 129.3%, a thermal stability factors (Δ) of 59.3 at room temperature, and robust endurance over 10¹² write cycles. These results confirm that combining elliptical MTJ designs with the CHL framework not only enables reliable, high-yield fabrication but also enhances the performance and energy efficiency of SOT-MRAM devices, offering a promising path toward scalable, low-power spintronic memory technologies.“

R&D: Advancing phase-change random access memory: materials innovation neuromorphic applications, and scalability challenges
Paper provides a comprehensive analysis of PRAM’s core operational mechanisms, including rapid switching speeds, high endurance, and multilevel storage enabled through precise control of phase transitions.

Journal of Physics D: Applied Physics has published an article written by Seoyoung Park, Minsuk Koo, Department of AI Semiconductor, School of Advanced Cross-Disciplinary Studies, University of Seoul, Seoul 02504, Republic of Korea, and Sungjun Kim, Division of Electronics and Electrical Engineering, Dongguk University, Seoul 04620, Republic of Korea.

Abstract: “Phase-change random access memory (PRAM) is an emerging high-speed, non-volatile memory technology that leverages the reversible phase transitions of chalcogenide materials such as Ge–Sb–Te to enable efficient data storage and retrieval. This paper provides a comprehensive analysis of PRAM’s core operational mechanisms, including rapid switching speeds, high endurance, and multilevel storage enabled through precise control of phase transitions. Recent advancements in materials engineering, such as nitrogen and carbon doping, superlattice-like structures, and thermoelectric effect integration, are explored for their contributions to improving thermal stability, endurance, and energy efficiency. Beyond traditional memory applications, PRAM’s unique ability to achieve tunable resistance states makes it a promising candidate for neuromorphic computing. The paper discusses PRAM’s role in emulating biological synaptic functions, such as synaptic weight modulation, spike-timing-dependent plasticity, and long-term potentiation/depression, enabling efficient learning and inference in artificial neural networks. The integration of PRAM into crossbar arrays and multi-memristive synapses is examined to develop scalable and energy-efficient neural network architectures for artificial intelligence applications. Key challenges, including sneak current phenomena, endurance degradation over repeated switching cycles, and power consumption in large-scale PRAM arrays, are critically analyzed. Potential solutions, such as selector devices, voltage scaling techniques, advanced thermal management strategies, and processing-in-memory architectures, are evaluated to address these issues. These advancements position PRAM as a pivotal technology for next-generation memory and neuromorphic computing, offering scalable, energy-efficient solutions for future high-performance and artificial intelligence-driven applications.“