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One method to improve the properties of covalent adaptable networks (CANs) is to reinforce them with a fraction of permanent cross‐links without sacrificing their (re)processability. Here, a simple method to synthesize poly(n‐hexyl methacrylate) (PHMA) and poly(n‐lauryl methacrylate) (PLMA) networks containing static dialkyl disulfide cross‐links (utilizing bis(2‐methacryloyl)oxyethyl disulfide, or DSDMA, as a permanent cross‐linker) and dynamic dialkylamino sulfur‐sulfur cross‐links (utilizing BiTEMPS methacrylate as a dissociative dynamic covalent cross‐linker) is presented. The robustness and (re)processability of the CANs are demonstrated, including the full recovery of cross‐link density after recycling. The authors also investigate the effect of static cross‐link content on the stress relaxation responses of the CANs with and without percolated, static cross‐links. As PHMA and PLMA have very different activation energies of their respective cooperative segmental mobilities, it is shown that the dissociative CANs without percolated, static cross‐links have activation energies of stress relaxation that are dominated by the dissociation of BiTEMPS methacrylate cross‐links rather than by the cooperative relaxations of backbone segments, i.e., the alpha relaxation. In CANs with percolated, static cross‐links, the segmental relaxation of side chains, i.e., the beta relaxation, is critical in allowing for large‐scale stress relaxation and governs their activation energies of stress relaxation. 

A reaction limited by standard diffusion is simulated stochastically to illustrate how the continuous time random walk (CTRW) formalism can be implemented with minimum statistical error. A step-by-step simulation of the diffusive random walk in one dimension reveals the fraction of surviving reactants P(t) as a function of time, and the time-dependent unimolecular reaction rate coefficient K(t). Accuracy is confirmed by comparing the time-dependent simulation to results from the analytical master equation, and the asymptotic solution to that of Fickian diffusion. An early transient feature is shown to arise from higher spatial harmonics in the Fourier distribution of walkers between reaction sites. Statistical ‘shot’ noise in the simulation is quantified along with the offset error due to the discrete time derivative, and an optimal simulation time interval t0 is derived to achieve minimal error in the finite time-difference estimation of the reaction rate. The number of walkers necessary to achieve a given error tolerance is derived, and W = 10^7 walkers is shown to achieve an accuracy of ±0.2% when the survival probability reaches P(t) ∼ 1/3 . The stochastic method presented here serves as an intuitive basis for understanding the CTRW formalism, and can be generalized to model anomalous diffusion-limited reactions to prespecified precision in regimes where the governing wait-time distributions have no analytical solution. 

Abstract Objective.Electrical impedance tomography (EIT) is a noninvasive imaging method whereby electrical measurements on the periphery of a heterogeneous conductor are inverted to map its internal conductivity. The EIT method proposed here aims to improve computational speed and noise tolerance by introducing sensitivity volume as a figure-of-merit for comparing EIT measurement protocols.Approach.Each measurement is shown to correspond to a sensitivity vector in model space, such that the set of measurements, in turn, corresponds to a set of vectors that subtend a sensitivity volume in model space. A maximal sensitivity volume identifies the measurement protocol with the greatest sensitivity and greatest mutual orthogonality. A distinguishability criterion is generalized to quantify the increased noise tolerance of high sensitivity measurements.Main result.The sensitivity volume method allows the model space dimension to be minimized to match that of the data space, and the data importance to be increased within an expanded space of measurements defined by an increased number of contacts.Significance.The reduction in model space dimension is shown to increasecomputational efficiency, accelerating tomographic inversion by several orders of magnitude, while the enhanced sensitivitytolerates higher noiselevels up to several orders of magnitude larger than standard methods. 

Abstract Antiferromagnetic (AFM) materials are a pathway to spintronic memory and computing devices with unprecedented speed, energy efficiency, and bit density. Realizing this potential requires AFM devices with simultaneous electrical writing and reading of information, which are also compatible with established silicon‐based manufacturing. Recent experiments have shown tunneling magnetoresistance (TMR) readout in epitaxial AFM tunnel junctions. However, these TMR structures are not grown using a silicon‐compatible deposition process, and controlling their AFM order required external magnetic fields. Here are shown three‐terminal AFM tunnel junctions based on the noncollinear antiferromagnet PtMn₃, sputter‐deposited on silicon. The devices simultaneously exhibit electrical switching using electric currents, and electrical readout by a large room‐temperature TMR effect. First‐principles calculations explain the TMR in terms of the momentum‐resolved spin‐dependent tunneling conduction in tunnel junctions with noncollinear AFM electrodes. 

An unconventional “heteromorphic” superlattice (HSL) is realized, comprised of repeated layers of different materials with differing morphologies: semiconducting pc-In2O3 layers interleaved with insulating a-MoO3 layers. Originally proposed by Tsu in 1989, yet never fully realized, the high quality of the HSL heterostructure demonstrated here validates the intuition of Tsu, whereby the flexibility of the bond angle in the amorphous phase and the passivation effect of the oxide at interfacial bonds serve to create smooth, high-mobility interfaces. The alternating amorphous layers prevent strain accumulation in the polycrystalline layers while suppressing defect propagation across the HSL. For the HSL with 7:7 nm layer thickness, the observed electron mobility of 71 cm2/Vs, matches that of the highest quality In2O3 thin films. The atomic structure and electronic properties of crystalline In2O3 / amorphous MoO3 interfaces are verified using ab-initio molecular dynamics simulations and hybrid functional calculations. This work generalizes the superlattice concept to an entirely new paradigm of morphological combinations. 

Abstract A scaling law is demonstrated in the conductivity of gated two-dimensional (2D) materials with tunable concentrations of ionized impurity scatterers. Experimental data is shown to collapse onto a single 2D conductivity scaling (2DCS) curve when the mobility is scaled by r , the relative impurity-induced scattering, and the gate voltage is shifted by V s , a consequence of impurity-induced doping. This 2DCS analysis is demonstrated first in an encapsulated 2D black phosphorus multilayer at T = 100 K with charge trap densities programmed by a gate bias upon cooldown, and next in a Bi 2 Se 3 2D monolayer at room temperature exposed to varying concentrations of gas adsorbates. The observed scaling can be explained using a conductivity model with screened ionized impurity scatterers. The slope of the r  vs.  V s plot defines a disorder-charge specific scattering rate Γ q = d r / d V s equivalent to a scattering strength per unit impurity charge density: Γ q > 0 indicates a preponderance of positively charged impurities with Γ q < 0 for negatively charged. This 2DCS analysis is expected to be applicable in arbitrary 2D materials systems with tunable impurity density, which will advance 2D materials characterization and improve performance of 2D sensors and transistors. 

Abstract There is accelerating interest in developing memory devices using antiferromagnetic (AFM) materials, motivated by the possibility for electrically controlling AFM order via spin-orbit torques, and its read-out via magnetoresistive effects. Recent studies have shown, however, that high current densities create non-magnetic contributions to resistive switching signals in AFM/heavy metal (AFM/HM) bilayers, complicating their interpretation. Here we introduce an experimental protocol to unambiguously distinguish current-induced magnetic and nonmagnetic switching signals in AFM/HM structures, and demonstrate it in IrMn 3 /Pt devices. A six-terminal double-cross device is constructed, with an IrMn 3 pillar placed on one cross. The differential voltage is measured between the two crosses with and without IrMn 3 after each switching attempt. For a wide range of current densities, reversible switching is observed only when write currents pass through the cross with the IrMn 3 pillar, eliminating any possibility of non-magnetic switching artifacts. Micromagnetic simulations support our findings, indicating a complex domain-mediated switching process.