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Recently, phase change chalcogenides, such as monochalcogenides, are reported as switching materials for conduction‐bridge‐based memristors. However, the switching mechanism focused on the formation and rupture of an Ag filament during the SET and RESET, neglecting the contributions of the phase change phenomenon and the distribution and re‐distribution of germanium vacancies defects. The different thicknesses of germanium telluride (GeTe)‐based Ag/GeTe/Pt devices are investigated and the effectiveness of phase loops and defect loops future application in neuromorphic computing are explored. GeTe‐based devices with thicknesses of 70, 100, and 200 nm, are fabricated and their electrical characteristics are investigated. Highly reproducible phase change and defect‐based characteristics for a 100 nm‐thick GeTe device are obtained. However, 70 and 200 nm‐thick devices are unfavorable for the reliable memory characteristics. Upon further analysis of the Ag/GeTe/Pt device with 100 nm of GeTe, it is discovered that a state‐of‐the‐art dependency of phase loops and defect loops exists on the starting and stopping voltage sweeps applied on the top Ag electrode. These findings allow for a deeper understanding of the switching mechanism of monochalcogenide‐based conduction‐bridge memristors. [ABSTRACT FROM AUTHOR]

Phase-change materials (PCMs), which can transition reversibly between crystalline and amorphous phases, have shown great promise for next-generation memory devices due to their nonvolatility, rapid switching periods, and random-access capability. Several groups have investigated phase-change nanowires for memory applications in recent years. The ability to regulate the scale of nanostructures remains one of the most significant obstacles in nanoscience. Herein, we describe the growth and characterization of germanium telluride (GeTe) nanowires, which are essential for phase-change memory devices. GeTe nanowires were produced by combining thermal evaporation and vapor–liquid–solid (VLS) techniques, using 8 nm Au nanoparticles as the metal catalyst. The influence of various growth parameters, including inert gas flow rate, working pressure, growth temperature, growth duration, and growth substrate, was examined. Ar gas flow rate of 30 sccm and working pressure of 75 Torr produced the narrowest GeTe nanowires horizontally grown on a Si substrate. Using scanning electron microscopy, the dimensions, and morphology of GeTe nanowires were analyzed. Transmission electron microscopy and energy-dispersive x-ray spectroscopy were utilized to conduct structural and chemical analyses. Using a SiO2/Si substrate produced GeTe nanowires that were thicker and lengthier. The current–voltage characteristics of GeTe nanowires were investigated, confirming the amorphous nature of GeTe nanowires using conductive atomic force microscopy. In addition, the effects of the VLS mechanism and the Gibbs–Thomson effect were analyzed, which enables the optimization of nanowires for numerous applications, such as memory and reservoir computing. [ABSTRACT FROM AUTHOR]

The authors report on the effect of manganese (Mn) substitution on the crystal chemistry, morphology, particle size distribution characteristics, chemical bonding, structure, and magnetic properties of cobalt ferrite (CoFe 2 O 4 ) nanoparticles (NPs) synthesized by a simple, cost-effective, and eco-friendly one-pot aqueous hydrothermal method. Crystal structure analyses indicate that the Mn(II)-substituted cobalt ferrites, Co 1- x Mn x Fe 2 O 4 (CMFO, x = 0.0-0.5), were crystalline with a cubic inverse spinel structure (space group Fd 3 m ). The average crystallite size increases from 8 to 14 nm with increasing Mn(II) content; the crystal growth follows an exponential growth function while the lattice parameters follow Vegard's law. Chemical bonding analyses made using Raman spectroscopic studies further confirm the cubic inverse spinel phase. The relative changes in specific vibrational modes related to octahedral sites as a function of Mn content suggest a gradual change of measure of inversion of the ferrite lattice at nanoscale dimensions. Small-angle X-ray scattering and electron microscopy revealed a narrow particle size distribution with the spherical shape morphology of the CMFO NPs. The zero-field-cooled and field-cooled magnetic measurements revealed the superparamagnetic behavior of CMFO NPs at room temperature. The sample with x = 0.3 indicates a lower value of blocking temperature (9.16 K) with the improved (maximum) value of saturation magnetization. The results and the structure-composition-property correlation suggest that the economic, eco-friendly hydrothermal approach can be adopted to process superparamagnetic nanostructured magnetic materials at a relatively lower temperature for practical electronic and electromagnetic device applications., Competing Interests: The authors declare no competing financial interest., (Copyright © 2020 American Chemical Society.)