Spin-transfer-torque magnetoresistive random-access memory (STT-MRAM) is an emerging nonvolatile memory that uses magnetic tunnel junctions (MTJs) to store information. MTJs with a crystalline MgO(001) tunnel barrier sandwiched between ferromagnetic layers, such as CoFeB, exhibit giant tunnel magnetoresistance, which is used to readout the STT-MRAM. Writing of STT-MRAM is based on current-induced magnetization reversal, called STT switching. STT-MRAM with perpendicular magnetization is especially important for high-density and low-power-consuming memory applications such as embedded memory for large-scale integrated circuit. For STT-MRAM to replace ultrahigh-density dynamic random-access memory, however, there are still technological challenges concerning the materials and fabrication processes of MTJs. This article reviews the physics and materials science of MTJs for STT-MRAM. We also discuss the importance of new MTJ materials and processes for next-generation ultrahigh-density MRAM.

Resistance switching random-access memory (ReRAM), with the ability to repeatedly modulate electrical resistance, has been highlighted as a feasible high-density memory with the potential to replace negative-AND flash memory. Such resistance modulation usually involves ion migration and filament formation, which usually lead to relatively low device reliability and yield. Resistance switching can also come from an entirely electronic origin, as in nanometallic memory, by electron trapping and detrapping. Recent research has revealed additional merits of its mechanism, which entails smart, atomic-sized floating gates that can be easily engineered in amorphous Si, oxides, and nitrides. This article addresses the basic ideas of nanometallic ReRAM, which may also be a contender for analogue computing and non-von Neumann-type computation.

Dynamic random-access memory (DRAM) is the main memory in most current computers. The excellent scalability of DRAM has significantly contributed to the development of modern computers. However, DRAM technology now faces critical challenges associated with further scaling toward the ∼10-nm technology node. This scaling will likely end soon because of the inherent limitations of charge-based memory. Much effort has been dedicated to delaying this. Novel cell architectures have been designed to reduce the cell area, and new materials and process technologies have been extensively investigated, especially for dielectrics and electrodes related to charge storage. In this article, the current issues, recent progress in and the future of DRAM materials, and fabrication technologies are discussed.

It is curious that first-principles quantum simulations for establishing the electronic structure and bonding patterns of molecules and materials are conducted using fields, yet the standard theoretical approach to understanding their thermal behavior, phase transitions, and self-assembly on larger length- and time scales relies on classical force fields acting on particle degrees of freedom. This article discusses how equilibrium models of classical particle assemblies can be exactly reframed as statistical field theories, and how these theories can be numerically simulated. Today, such field-theoretic simulations have emerged as a highly efficient way to study phase transitions and self-assembly behavior in broad classes of soft materials, including block polymers, polyelectrolyte complexes, and polymeric emulsions.

Perovskites solar cells have reached impressive efficiencies (22%) in recent years. Because certain environmental concerns are raised by the use of lead halides, there is an interest to seek out lead-free alternatives, featuring bismuth or antimony. Alongside, one of the major drawbacks displayed by MAPbI3 is their low stability at ambient conditions. In this work, (RP4)xBiyIz were synthesized, using different types of tetra-alkylphosphoniums (R4PI) were R = ethyl, butyl, hexyl, and octyl, to assess their stability. Afterwards, they were characterized to study their morphology and crystal structure, as well as their optical properties.

Evolving from the oblique-angle deposition method used industrially for the deposition of thin films, the conformal-evaporated-film-by-rotation (CEFR) technique has been successfully applied to replicate surfaces of biologic origin. The CEFR technique is the first step of the Nano4Bio technique, an industrially scalable bioreplication process, the other three steps being electroforming, plasma ashing, and either stamping or casting. These techniques have found optical applications in diverse fields, including forensic science, pest control, and light sources.

We present a method for measuring the shear complex modulus of hydrogels by oscillatory nanoindentation, with unprecedented attention to procedure and uncertainty analysis. The method is verified by testing a typical low-molecular-weight gelator formed from the controlled hydrolysis of glucono-δ-lactone. Nanoindentation results are compared with those obtained by rheometry using both vane-in-cup and parallel-plate fixtures. At 10 Hz, the properties measured by oscillatory nanoindentation were G′ = 38.1 ± 2.8 kPa, tan δ = 0.22 ± 0.02. At the same frequency, the properties measured by rheometry were G′ = 15.3 ± 2.9 kPa, tan δ = 0.11 ± 0.016 (vane-in-cup) and G′ = 7.9 ± 1.1 kPa, tan δ = 0.05 ± 0.004 (parallel-plate). The larger shear modulus measured by nanoindentation is due to the scale of testing. Whereas rheometry characterizes the bulk material response, nanoindentation probes the fibrous network of the gel. The procedure and analysis presented here are valuable for nanoindentation testing of other compliant materials such as hydrogels, soft biological tissue, and food products.