A quantum sensing metrology for magnetic memories

Magnetic random access memory (MRAM) is a leading emergent memory technology that is poised to replace current non-volatile memory technologies such as eFlash. However, the scaling of MRAM technologies is heavily affected by device-to-device variability rooted in the stochastic nature of the MRAM writing process into nanoscale magnetic layers. Here, we introduce a non-contact metrology technique deploying Scanning NV Magnetometry (SNVM) to investigate MRAM performance at the individual bit level. We demonstrate magnetic reversal characterization in individual, < 60 nm sized bits, to extract key magnetic properties, thermal stability, and switching statistics, and thereby gauge bit-to-bit uniformity. We showcase the performance of our method by benchmarking two distinct bit etching processes immediately after pattern formation. Unlike previous methods, our approach unveils marked differences in switching behaviour of fully contacted MRAM devices stemming from these processes. Our findings highlight the potential of nanoscale quantum sensing of MRAM devices for early-stage screening in the processing line, paving the way for future incorporation of this nanoscale characterization tool in the semiconductor industry

Auto-inflammation pilotée par injection de radicaux (APIR) (influence de l'aérodynamique interne et des concentrations locales sur l'initiation de la combustion)

Une des principales préoccupations du 21e siècle est la pollution atmosphérique, qui est en partie due à l'utilisation des moteurs à combustion interne. L'une des voies envisageables pour diminuer les émissions polluantes des moteurs à combustion interne est l'utilisation de mélanges pauvres. La technologie actuelle des moteurs ne permet pas d'enflammer de manière efficace les mélanges pauvres. Ce travail est consacré à l'étude d'un dispositif d'initiation de la combustion : l'auto-inflammation pilotée par injection de radicaux. Tout d'abord, les différents types de combustion moteur sont décrits ainsi que différents dispositifs d'initiation de la combustion. Les avantages et les inconvénients de chaque mode de combustion sont exposés. Puis, l'APIR est étudié en détail. Nous démontrons que l'APIR se déroule en quatre étapes : la combustion d'un mélange riche dans la préchambre, l'ensemencement en produits intermédiaires de combustion de la chambre principale, l'auto-inflammation de multiples sites dans la chambre principale, et la combustion du reste de la charge par la propagation de fronts de flamme. Nous étudions aussi l'influence de paramètres tels, le volume et le matériau de la préchambre, le diamètre et l'orientation des conduits de la préchambre, sur les performances de l'APIR. Enfin, une comparaison est effectuée entre l'APIR et la bougie classique On constate que l'APIR permet de réduire la consommation et la production de NOx sur certains points moteur. Ce travail montre que l'APIR a un grand potentiel en terme de réduction de la consommation et des émissions polluantes bien que les dispositifs, qui ont été utilisés pendant ce travail, ne sont pas optimisés.ORLEANS-BU Sciences (452342104) / SudocSudocFranceF

Effects of a Pseudophysiological Environment on the Elastic and Viscoelastic Properties of Collagen Gels

Vascular tissue engineering focuses on the replacement of diseased small-diameter blood vessels with a diameter less than 6 mm for which adequate substitutes still do not exist. One approach to vascular tissue engineering is to culture vascular cells on a scaffold in a bioreactor. The bioreactor establishes pseudophysiological conditions for culture (medium culture, 37°C, mechanical stimulation). Collagen gels are widely used as scaffolds for tissue regeneration due to their biological properties; however, they exhibit low mechanical properties. Mechanical characterization of these scaffolds requires establishing the conditions of testing in regard to the conditions set in the bioreactor. The effects of different parameters used during mechanical testing on the collagen gels were evaluated in terms of mechanical and viscoelastic properties. Thus, a factorial experiment was adopted, and three relevant factors were considered: temperature (23°C or 37°C), hydration (aqueous saline solution or air), and mechanical preconditioning (with or without). Statistical analyses showed significant effects of these factors on the mechanical properties which were assessed by tensile tests as well as stress relaxation tests. The last tests provide a more consistent understanding of the gels' viscoelastic properties. Therefore, performing mechanical analyses on hydrogels requires setting an adequate environment in terms of temperature and aqueous saline solution as well as choosing the adequate test

Spin-orbit torque switching of magnetic tunnel junctions for memory applications

International audienceSpin-orbit torques (SOT) provide a versatile tool to manipulate the magnetization of diverse classes of materials and devices using electric currents, leading to novel spintronic memory and computing approaches. In parallel to spin transfer torques (STT), which have emerged as a leading non-volatile memory technology, SOT broaden the scope of current-induced magnetic switching to applications that run close to the clock speed of the central processing unit and unconventional computing architectures. In this paper, we review the fundamental characteristics of SOT and their use to switch magnetic tunnel junction (MTJ) devices, the elementary unit of the magnetoresistive random access memory (MRAM). In the first part, we illustrate the physical mechanisms that drive the SOT and magnetization reversal in nanoscale structures. In the second part, we focus on the SOT-MTJ cell. We discuss the anatomy of the MTJ in terms of materials and stack development, summarize the figures of merit for SOT switching, review the field-free operation of perpendicularly magnetized MTJs, and present options to combine SOT, STT and voltage-gate assisted switching. In the third part, we consider SOT-MRAMs in the perspective of circuit integration processes, introducing considerations on scaling and performance, as well as macro-design architectures. We thus bridge the fundamental description of SOT-driven magnetization dynamics with an application-oriented perspective, including device and system-level considerations, goals, and challenges

Spin-orbit torque switching of magnetic tunnel junctions for memory applications

Spin-orbit torques (SOT) provide a versatile tool to manipulate the magnetization of diverse classes of materials and devices using electric currents, leading to novel spintronic memory and computing approaches. In parallel to spin transfer torques (STT), which have emerged as a leading non-volatile memory technology, SOT broaden the scope of current-induced magnetic switching to applications that run close to the clock speed of the central processing unit and unconventional computing architectures. In this paper, we review the fundamental characteristics of SOT and their use to switch magnetic tunnel junction (MTJ) devices, the elementary unit of the magnetoresistive random access memory (MRAM). In the first part, we illustrate the physical mechanisms that drive the SOT and magnetization reversal in nanoscale structures. In the second part, we focus on the SOT-MTJ cell. We discuss the anatomy of the MTJ in terms of materials and stack development, summarize the figures of merit for SOT switching, review the field-free operation of perpendicularly magnetized MTJs, and present options to combine SOT, STT and voltage-gate assisted switching. In the third part, we consider SOT-MRAMs in the perspective of circuit integration processes, introducing considerations on scaling and performance, as well as macro-design architectures. We thus bridge the fundamental description of SOT-driven magnetization dynamics with an application-oriented perspective, including device and system-level considerations, goals, and challenges.ISSN:0304-885