R&D : Five Articles on Phase Change Memories Technologies

R&D: Femtosecond laser irradiation of Ge-Rich Ge-Sb-Te in thin films and multilayer structures for phase-change memory
Study demonstrates that femtosecond laser pulses can efficiently induce amorphization in Ge-rich Ge-Sb-Te (GGST) thin films and GST/GGST multilayer structures.

Applied Surface Science has published an article written by Keerati Meeporn, Mathieu Abel, Walter Batista-Pessoa, Aix-Marseille University, CNRS, IM2NP UMR 7334, Marseille Cedex 20 13397, France, Nicolas Botti, Aix-Marseille University, CNRS, IM2NP UMR 7334, Marseille Cedex 20 13397, France, Aix-Marseille University, CNRS, LP3 UMR 7341, Marseille 13009, France, and STMicroelectronics, 850 Rue Jean Monnet, Crolles 38920, France, Mania Majumder, Pol Sopeña, Aix-Marseille University, CNRS, LP3 UMR 7341, Marseille 13009, France, Yannick Le-Friec, STMicroelectronics, 850 Rue Jean Monnet, Crolles 38920, France, Elisa Petroni, STMicroelectronics, Camillo Olivetti, 2, Agrate Brianza, MB 20864, Italy, Mathieu Koudia, Aix-Marseille University, CNRS, IM2NP UMR 7334, Marseille Cedex 20 13397, France, David Grojo, Aix-Marseille University, CNRS, LP3 UMR 7341, Marseille 13009, France, and Isabelle Berbezier, Aix-Marseille University, CNRS, IM2NP UMR 7334, Marseille Cedex 20 13397, France.

Abstract: “This study demonstrates that femtosecond laser pulses can efficiently induce amorphization in Ge-rich Ge-Sb-Te (GGST) thin films and GST/GGST multilayer structures. Using cross-sectional scanning transmission electron microscopy (STEM), we examined the structural evolution of undoped and compositionally stabilized GGST films under different femtosecond laser fluences. In both type of samples, a single laser pulse triggered significant structural transformations, including grain dissolution, lattice disorder, and the formation of an amorphous matrix. Two distinct transformation mechanisms were identified: thermal melting followed by rapid quenching and non-thermal bond destabilization via electronic excitation. These findings are supported by high-resolution STEM imaging, SAED patterns, and elemental mapping. Furthermore, successful amorphization was achieved in complex multi-layered architectures composed of alternating GST and GGST layers, underscoring the applicability of femtosecond laser-induced amorphization in advanced phase-change memory (PCM) structures. These results validate the feasibility of ultrafast optical amorphization in GGST single layers and GST/GGST multilayer structures, and provide critical insights for the rational design of next-generation laser-programmable phase-change materials for practical memory device applications.“

R&D: ML-PCM, Machine Learning Technique for Write Optimization in Phase Change Memory (PCM)
Paper proposes the use of a neural network (NN) model to predict critical parameters such as write latency, energy consumption, and endurance by monitoring real-time operating conditions and device characteristics.

arXiv has published an article written by Mahek Desai, California State University, Northridge, USA, Rowena Quinn, Illinois Central College, Peoria, USA, and Marjan Asadinia, California State University, Northridge, USA.

Abstract: “As transistor-based memory technologies like dynamic random access memory (DRAM) approach their scalability limits, the need to explore alternative storage solutions becomes increasingly urgent. Phase-change memory (PCM) has gained attention as a promising option due to its scalability, fast access speeds, and zero leakage power compared to conventional memory systems. However, despite these advantages, PCM faces several challenges that impede its broader adoption, particularly its limited lifespan due to material degradation during write operations, as well as the high energy demands of these processes. For PCM to become a viable storage alternative, enhancing its endurance and reducing the energy required for write operations are essential. This paper proposes the use of a neural network (NN) model to predict critical parameters such as write latency, energy consumption, and endurance by monitoring real-time operating conditions and device characteristics. These predictions are key to improving PCM performance and identifying optimal write settings, making PCM a more practical and efficient option for data storage in applications with frequent write operations. Our approach leads to significant improvements, with NN predictions achieving a Mean Absolute Percentage Error (MAPE) of 0.0073% for endurance, 0.23% for total write latency, and 4.92% for total write energy.“

R&D: Flexible phase change memory based on Si-Sb-Te thin film, research on anti-bending mechanism and high-speed operating performance
Study develops silicon-doped Sb₂Te₃ films on polyimide (PI) substrates for flexible phase change memory (FPCM), demonstrating maintained phase transition functionality after bending, although repeated bending degrades thermal stability and crystalline structure.

Applied Surface Science has published an article written by Yukun Wang, School of Mathematics and Physics, The Jiangsu Key Laboratory of Clean Energy Storage and Conversion, Jiangsu University of Technology, Changzhou 213000, China, Shiwei Gao, Liangcai Wu, College of Physics, Donghua University, Shanghai 201620, China, and Yifeng Hu, School of Mathematics and Physics, The Jiangsu Key Laboratory of Clean Energy Storage and Conversion, Jiangsu University of Technology, Changzhou 213000, China.

Abstract: “This study develops silicon-doped Sb₂Te₃ films on polyimide (PI) substrates for flexible phase change memory (FPCM), demonstrating maintained phase transition functionality after bending, although repeated bending degrades thermal stability and crystalline structure. XPS analysis confirms silicon doping induces partial Sb substitution by Si with Si-Te bond formation, while SEM reveals bending-induced surface cracks and significant silicon depletion. FPCM bridge devices fabricated from this Si-Sb-Te material via photolithography show superior performance at reduced dimensions: devices with a 2 μm line width outperform 5 μm counterparts, achieving faster switching (∼6 ns) and greater endurance (∼150 cycles). Crucially, under a 5 mm bending radius, these devices retain distinct high and low resistance states after 10,000 bending cycles, demonstrating exceptional mechanical robustness. This work provides a viable strategy for enhancing both the operational speed and bending tolerance of FPCM devices.“

R&D: Structural destabilization and optoelectronic degradation of crystalline Ge₂Sb₂Te₅ phase-change memory in low-earth orbit, a multiscale simulation study
Findings establish a clear mechanistic foundation for irradiation-induced disorder in GST and offer methodological insights that can guide the design of radiation-resilient phase-change memory technologies for aerospace applications.

Results in Engineering has published an article written by Zulfiqar Ali, Furong Liu, Key Laboratory of Trans-scale Laser Manufacturing (Beijing University of Technology), Ministry of Education, Beijing 100124, China and School of Physics and Optoelectronic Engineering, Beijing University of Technology, Beijing 100124, China, Yinghao Wang, National Space Science Center, Chinese Academy of Sciences, Beijing 100190, China, Salem Algarni, Talal Alqahtani, Mechanical Engineering Department, College of Engineering, King Khalid University, Abha 9004, Saudi Arabia, and Center for Engineering and Technology Innovation, King Khalid University, Abha 61421, Saudi Arabia, Kashif Irshad, Mechanical Engineering Department, King Fahd University of Petroleum & Minerals, Dhahran 31261, Saudi Arabia, and Interdisciplinary Research Centre for Sustainable Energy Systems (IRC-SES), Research Institute, King Fahd University of Petroleum & Minerals (KFUPM), Dhahran, 31261, Saudi Arabia, and Hasan Shahzad, Centro Ibérico de Investigación en Almacenamiento Energético, Careces (CIIAE), 10004, Spain, and Interdisciplinary Research Centre for Sustainable Energy Systems (IRC-SES), Research Institute, King Fahd University of Petroleum & Minerals (KFUPM), Dhahran, 31261, Saudi Arabia.

Abstract: “The development of radiation-tolerant phase-change memories is essential for next-generation space technologies, yet their structural and optoelectronic responses to electron irradiation in low-Earth-orbit (LEO) environments remain insufficiently understood. In this work, we integrate ab initio molecular dynamics (AIMD) with Monte Carlo (MC) simulations to uncover the atomistic damage mechanisms governing crystalline Ge₂Sb₂Te₅ (GST). Our directional and sublayer-resolved analyses show that radiation susceptibility and resilience are strongly governed by variations in Milliken bond populations (MBP) and the corresponding local bonding strengths within the GST lattice. Notably, van der Waals (vdW) planes with higher MBP act as defect sinks, buffering displacement cascades at threshold levels. AIMD simulations reveal lower energy damage thresholds for Te primary knock-on atoms (PKAs) than for Sb and Ge, leading to earlier onset of order–disorder transitions and metallic collapse. Void formation at these damage thresholds promotes the accumulation of wrong bonds and homopolar configurations, whereas non-void cascades preferentially maintain ABAB stacking motifs and exhibit higher structural resilience. This contrast is consistently supported by short- and medium-range order metrics, as well as by our newly introduced Milliken Ring Population (MRP) analysis. At the electronic damage dose (∼3 × 10⁵ MeV/g), GST exhibits rapid band-gap collapse, a sharp rise in the imaginary dielectric function, and a pronounced decline in the real dielectric function, most severe for Te PKAs. These findings establish a clear mechanistic foundation for irradiation-induced disorder in GST and offer methodological insights that can guide the design of radiation-resilient phase-change memory technologies for aerospace applications.“

R&D: Electronic and thermal properties of the phase-change memory material, GeSbTe, and results from spatially resolved transport calculations
Authors report new insights into the electronic, structural, and transport (heat and charge) properties of the phase-change memory material amorphous GeSbTe.

Solid State Sciences has published an article written by K. Nepal, A. Gautam, R. Hussein, Department of Physics and Astronomy, Nanoscale and Quantum Phenomena Institute (NQPI), Ohio University, Athens, 45701, OH, USA, K. Konstantinou, Department of Mechanical and Materials Engineering, University of Turku, Turku, FI-20500, Finland, S.R. Elliott, Physical and Theoretical Chemistry Laboratory, Department of Chemistry, University of Oxford, Oxford, OX1 3QZ, UK, C. Ugwumadu, Physics of Condensed Matter and Complex Systems (T-4) Group, Los Alamos National Laboratory, Los Alamos, NM, USA, and D.A. Drabold, Department of Physics and Astronomy, Nanoscale and Quantum Phenomena Institute (NQPI), Ohio University, Athens, 45701, OH, USA.

Abstract: “We report new insights into the electronic, structural, and transport (heat and charge) properties of the phase-change memory material amorphous GeSbTe. Using realistic structural models of Konstantinou et al., (2019), we analyze the topology, electronic states, and lattice dynamics with density functional methods, including hybrid-functional calculations and machine-learned interatomic potentials. The Kohn–Sham orbitals near the Fermi level display a strong electron–phonon coupling, and exhibit large energy fluctuations at room temperature. The conduction tail states exhibit larger phonon-induced fluctuations than the valence tail states. To resolve transport at the atomic scale, we employ space-projected electronic conductivity and site-projected thermal conductivity methods. Local analysis of heat transport highlights the role of filamentary networks dominated by Te, with Sb and Ge making progressively smaller contributions.“