M81-SSM REFERENCES IN RESEARCH LITERATURE

Many electronic and electrochemical devices rely on the exchange of light elements such as hydrogen and oxygen with the environment. Understanding and tailoring the device functionality requires accurate information about the concentration and chemical bonding of such species inside a solid, which is particularly difficult if several species are exchanged. In LaNiO₃ thin films in situ transport experiments reveal a re-entrant metal–insulator transition upon hydrogen exposure. The origin of this unusual behavior can be understood by combining information about the stoichiometry and chemical bonding of hydrogen and oxygen as determined by neutron reflectometry and x-ray absorption spectroscopy, respectively. In addition to the metallic parent phase, an insulating phase with composition LaNiO_2.65 and a re-entrant metallic phase with composition LaNiO_2.15(OH)_0.5 are identified. They can be inter-converted by redox reactions in different external environments. The methodology employed offers new insights into the mechanisms underlying the influence of hydrogen in functional devices. 

Materials that combine distinct properties within a single phase are of fundamental and technological interest^1–9. However, it is challenging to harmoniously combine various properties, particularly since some physical properties are inherently mutually exclusive^10–12. The artificial integration of these mutually exclusive properties could lead to innovative physical phenomena and functionalities, unattainable from conventional approaches. This has recently motivated extensive studies to artificially create bulk polarity and integrate it with seemingly incompatible electronic and structural properties^13–16. However, the scope of their applications and the derived functionalities remain largely limited. Here, we present a universal strategy to achieve strong bulk polarity that not only coexists with its originally incompatible properties, such as metallicity, but also synergistically enables exceptional functionalities. A combination of thin-film synthesis, atomic-scale imaging, and theoretical calculations reveals that A-site selective atomic gradients induce strong polar states in otherwise centrosymmetric perovskite oxides ABO₃. These polar states unconventionally coexist with various preexisting properties, leading to bulk polar metallicity with tunable nonreciprocal transport, high-κ dielectricity with an equivalent oxide thickness below 0.1 nm, and giant pyroelectricity. This work will facilitate the development of new multifunctional materials with unusual coexisting and synergistic properties.

All-Van der Waals (vdW)-material-based heterostructures with atomically sharp interfaces offer a versatile platform for high-performing spintronic functionalities at room temperature. One of the key components is vdW topological insulators (TIs), which can produce a strong spin-orbit-torque (SOT) through the spin-momentum locking of their topological surface state (TSS). However, the relatively low conductance of the TSS introduces a current leakage problem through the bulk states of the TI or the adjacent ferromagnetic metal layers, reducing the interfacial charge-to-spin conversion efficiency (q_ICS). Here, a vdW heterostructure is used consisting of atomically-thin layers of a bulk-insulating TI Sn-doped Bi_1.1Sb_0.9Te₂S₁ and a room-temperature ferromagnet Fe₃GaTe_2, to enhance the relative current ratio on the TSS up to ≈20%. The resulting q_ICS reaches ≈1.65 nm⁻¹ and the critical current density J_c ≈0.9 × 10⁶ Acm⁻² at 300 K, surpassing the performance of TI-based and heavy-metal-based SOT devices. These findings demonstrate that an all-vdW heterostructure with thickness optimization offers a promising platform for efficient current-controlled magnetization switching at room temperature.

We have investigated the magnetic, thermodynamic, and electrical transport properties of EuAuSb single crystals as well as carrying out band structure calculations. The powder x-ray diffraction data confirm that EuAuSb crystallizes in ZrBeSi-type hexagonal structure with space group P63/mmc. The magnetic measurements reveal an antiferromagnetic (AFM) ordering in EuAuSb at TN=3.3 K. This transition is further confirmed by heat capacity and electrical resistivity data. The isothermal magnetization data saturate at low magnetic field of μ0Hcs=2.9 and μ0Habs=3.8 T for H⊥c and H∥c, respectively, while the magnetization along H⊥c displays a metamagnetic transition around μ0Habm=0.95 T. The electrical resistivity exhibits a metallic behavior down to 35 K; after that it shows an upturn until TN due to the influence of short-range interactions. The longitudinal and transverse magnetoresistances of EuAuSb are negative (∼−45% and −42% in 10 T at 2 K, respectively); in the high field at T≤40 K, they switch to a positive value above 40 K. Further, we observe a humplike anomaly in the Hall resistivity [ρxy(H)] data below TN, which is most likely a manifestation of the topological Hall effect. Our two-band model analysis of ρxy(H) data indicates both hole and electron charge carriers contribute to the electrical transport of the compound. The electronic band structure calculations reveal a Γ-centered nodal line in the absence of spin-orbit coupling (SOC). In the presence of SOC, the compound hosts the Dirac point. The Z2 invariants, in the presence of effective time-reversal and inversion symmetries, categorize this system as a nontrivial topological material. Our combined experimental and theoretical studies suggest EuAuSb to be a potential AFM topological semimetal.

When using high-sensitivity sensors in arrays, it is essential to divide the sensor system into individual, robust and separable components. This is the most effective way to achieve a sufficient sensor density and to make efficient use of techniques such as multiplexing. This paper presents a compact surface acoustic wave (SAW) oscillator ring composed of discrete components for magnetic field measurement. The output signal of the oscillator is the frequency modulated (FM) sensor signal and can be directly demodulated or down-converted for demodulation, depending on the operating frequency of the sensitive element.

Lock-in amplifiers are instrumental in the precise measurement of extremely small AC signals within high-noise environments. Traditionally, noise reduction in these instruments relies on infinite impulse response (IIR) filters, which can necessitate prolonged settling times to ensure the acquisition of accurate, statistically independent data. While moving average filters offer faster settling times, their non-monotonic frequency response may not be optimal for noise reduction. Conversely, IIR filters frequently realized as N-pole RC filters exhibit a monotonic frequency response conducive to effective noise reduction. This study presents a hybrid filter architecture that combines a short IIR filter with a longer moving average finite impulse response filter. The objective is to enhance noise reduction as quantified by the filter’s equivalent noise bandwidth (ENBW). Theoretical analysis is provided to derive the step response, settling time, frequency response, and ENBW of the hybrid filter configuration. Design methodologies are outlined for hybrid filters that either match the settling time of an N-pole RC filter while achieving a lower ENBW or maintain the ENBW of an N-pole RC filter but with significantly faster settling time. The performance of the hybrid filter is validated through noise measurements of low-value resistors and thermal noise of larger resistors, with results compared to theoretical predictions.

Graphene nanoribbons (GNRs), when synthesized with atomic precision by bottom–up chemical approaches, possess tunable electronic structure, and high theoretical mobility, conductivity, and heat dissipation capabilities, which makes them an excellent candidate for channel material in post-silicon transistors. Despite their immense potential, achieving highly transparent contacts for efficient charge transport—which requires proper contact selection and a deep understanding of the complex one-dimensional GNR channel-three-dimensional metal contact interface—remains a challenge. In this study, we investigated the impact of different electron-beam deposited contact metals—the commonly used palladium (Pd) and softer metal indium (In)—on the structural properties and field-effect transistor performance of semiconducting nine-atom wide armchair GNRs. The performance and integrity of the GNR channel material were studied by means of a comprehensive Raman spectroscopy analysis, scanning tunneling microscopy (STM) imaging, optical absorption calculations, and transport measurements. We found that, compared to Pd, In contacts facilitate favorable Ohmic-like transport because of the reduction of interface defects, while the edge structure quality of GNR channel plays a more dominant role in determining the overall device performance. Our study provides a blueprint for improving device performance through contact engineering and material quality enhancements in emerging GNR-based technology.

Revealing the electro-mechanical contact characteristics between rough surfaces at extreme temperatures is critical to accurately assessing the service performance of equipment in aerospace, energy and other fields. In this paper, a theoretical model of electro-mechanical contact behavior at extreme temperatures is developed based on the consideration of the effect of temperature on material property parameters and interfacial morphologies. It reveals the mechanism of temperature variation on the contact behavior of rough surfaces. The results show large temperature changes affect the contact resistance and the real contact area, because of the in significantly different contact behavior between high temperature and low temperature. This study helps us to gain a deeper understanding of the effects of extreme temperatures on the contact behavior and provides a reference for the design of interfacial conductivity in engineering structures. 

Atomically precise graphene nanoribbons (GNRs) synthesized from the bottom-up exhibit promising electronic properties for high-performance field-effect transistors (FETs). The feasibility of fabricating FETs with GNRs (GNRFETs) has been demonstrated, with ongoing efforts aimed at further improving their performance. However, their long-term stability and reliability remain unexplored, which is as important as their performance for practical applications. In this work, we fabricated short-channel FETs with nine-atom-wide armchair GNRs (9-AGNRFETs). We revealed that the on-state (I_ON) current performance of the 9-AGNRFETs deteriorates significantly over consecutive full transistor on and off logic cycles, which has neither been demonstrated nor previously considered. To address this issue, we deposited a thin ∼10 nm thick atomic layer deposition (ALD) layer of aluminum oxide (Al₂O₃) directly on these devices. The integrity, compatibility, electrical performance, stability, and reliability, of the GNRFETs before and/or after Al₂O₃ deposition were comprehensively studied. The results indicate that the observed decline in electrical device performance is most likely due to the degradation of contact resistance over multiple measurement cycles. We successfully demonstrated that the devices with the Al₂O₃ layer operate well up to several thousand continuous full cycles without any degradation. Our study offers valuable insights into the stability and reliability of GNR transistors, which could facilitate their large-scale integration into practical applications. 

The effects of pressure on the structure and electrical transport properties, including electrical resistance and critical magnetic field values for superconductivity in pristine and hydrogenated TiZr alloys, were investigated. As pressure increased from ambient to 55 GPa, the structure of the pristine TiZr alloys transformed from hcp to bcc via an intermediate ω phase. The superconducting transition temperature (Tc) significantly increased from 1.76 K at ambient pressure to 15.5 K at 52.2 GPa, accompanied by an extrapolated upper critical field of 24.5 T at T = 0 K. In contrast, the hydrogenated samples exhibited substantially lower Tc values compared to the pristine ones, with a Tc of 4.6 K at 50.5 GPa and an extrapolated upper critical field of 1.8 T at T = 0 K. Upon decompression, the superconductivity in the hydrogenated sample persisted down to 25 GPa, disappearing when the pressure was reduced to 19 GPa. Synchrotron X-ray diffractions (XRD) analysis revealed the formation of three hydrides: I4/mmm-(Ti, Zr)H2, P63/mmc-(Ti, Zr)H3, and I4̅3d-(Ti,Zr)4H15. By combining XRD and electrical resistance data, we tentatively propose that the P63/mmc-(Ti, Zr)H3 predominantly induces superconductivity. In contrast to superhydrides, where electron–phonon interactions increase the superconducting temperature at high pressure, hydrogen atoms in hcp-(Ti, Zr)H3 reduce Tc.