All-electrical magnetization control by spin currents is a critical step toward low-power, nonvolatile, and programmable spin logic. Here, using magnetization dynamics simulations, we demonstrate a field-free switching scheme driven by two orthogonal spin-current pulses with a temporal offset. Deterministic perpendicular magnetization switching is achieved when both field-like and damping-like spin–orbit torques are present. The first pulse tilts the magnetization into the plane, while the second breaks torque symmetry to select the final state. The switching polarity is governed solely by the relative orientations of the two pulses and is independent of the initial magnetization state. Employing orthogonal currents as input variables, all 16 Boolean logic functions are implemented within a single device. This field-free switching mechanism and Boolean logic functionality are fully compatible with industry-standard magnetic tunnel junctions, paving a practical route toward all-electrical spin-based in-memory computing.
Patterned-transducer frequency-domain thermoreflectance (FDTR) enhances sensitivity to low-thermal-conductivity materials by suppressing lateral heat spreading within the metal transducer. However, the finite patterned geometry is not directly described by conventional analytical models formulated for laterally unbounded transducers, making iterative parameter fitting based on finite-element simulations computationally prohibitive. Here, we develop a reduced-order surrogate model, enhanced by transfer learning, that directly predicts the FDTR phase response for rapid inverse thermal-property extraction. Within the original training domain, the surrogate achieves a mean phase root mean square error of 0.19° relative to the full-order comsol simulations and accelerates forward prediction by 534-fold, reducing a representative three-parameter fit from more than 5 h to approximately 1 min. Measurements of Al/SiO2 samples yield consistent silica thermal conductivities using conventional and patterned transducers, validating the surrogate-based fitting framework. For anisotropic Z-cut LiNbO3, the method yields radial and cross-plane thermal conductivities of 3.35 ± 0.19 and 3.80±0.75W/(mK), respectively, in close agreement with independent time-domain thermoreflectance measurements on the same material. Transfer learning extends the surrogate to broader parameter domains using only 1000 new simulations, compared with 6000 used to develop the original model, while outperforming direct training under the same target-domain data budget. This framework enables rapid inverse thermal characterization for complex measurement geometries where repeated high-fidelity forward simulations would otherwise be computationally prohibitive.
γ-CuI is an intrinsically p-type semiconductor with considerable potential for transparent optoelectronic devices owing to its wide bandgap (∼3.1 eV) and high carrier mobility [>40 cm2/(V s) in bulk]. However, the epitaxial growth of high-quality γ-CuI films is hindered by the large lattice mismatch with conventional transparent single-crystal substrates. In this study, we demonstrate the direct domain epitaxy of γ-CuI films on MgO (111) substrates via physical vapor transport (PVT), despite a conventional lattice mismatch of 43.4%. The films exhibit a preferred out-of-plane (111) orientation and triangular crystalline domains with distinct terrace-and-step features. X-ray diffraction φ-scan and electron backscatter diffraction analyses reveal two in-plane domains rotated by 60° relative to each other. Combined with transmission electron microscopy results, these analyses establish the epitaxial relationship between the γ-CuI film and the MgO substrate as γ-CuI ⟨112¯⟩ (111)//MgO [01¯1] (111) and identify an interfacial 4/5 lattice-plane matching relationship, which results in a residual mismatch of approximately 0.57%. The films exhibit an average visible transmittance of more than 85% and an optical bandgap of approximately 3.01 eV. Hall measurements reveal p-type conductivity, with a hole mobility of 14.93 cm2/(V s) and an electrical conductivity of 0.70 S/cm. These results demonstrate that the direct domain epitaxy of γ-CuI on a highly lattice-mismatched MgO (111) substrate is achievable through interfacial multiplane matching using the PVT method.
Characterizing metal–semiconductor contacts, particularly detecting Schottky barriers and distinguishing between ohmic and Schottky contacts, is essential for developing efficient semiconductor devices. Off-axis electron holography enables direct visualization of electrostatic potentials in a transmission electron microscope and has previously been used to study semiconductor p–n junctions under applied bias. Here, it is demonstrated that in situ biasing off-axis electron holography enables the direct characterization of the electrical properties of Schottky and ohmic metal–semiconductor contacts, including the visualization and quantification of Schottky depletion widths while simultaneously probing the behavior of the semiconductor p–n junction under operating conditions. To demonstrate this, Pt and W contacts with intentionally low and high contact resistance were deposited on GaAs p–n diodes using Ga-focused ion beam-induced deposition. The electrostatic potential across the metal–GaAs interface and p–n junction was mapped using electron holography under applied reverse bias. Electron holography successfully detected and quantified the Schottky depletion width in situ at the interface between W and p-GaAs and confirmed the ohmic behavior of the Pt contact to p-GaAs, demonstrating that electron holography can directly distinguish and characterize Schottky and ohmic contacts while simultaneously probing the behavior of the p–n junction. Thus, the results demonstrate its effectiveness for measuring nanoscale contacts in operating devices.
We propose a quantum-confined planar vacuum triode, a mesoscopic vacuum device in which electron transport is controlled by quantum confinement in a nanoscale vacuum channel. Unlike conventional vacuum triodes based on electrostatic electron deflection, the proposed device operates through competition between longitudinal tunneling to the anode and transverse tunneling to the gate. A gate-controlled redistribution of the electron flux between these channels leads to a sharp suppression of the output current. The quantum transport model predicts terahertz-range operation with cutoff frequencies of 0.5–5 THz and reduced shot noise due to quantum partitioning. The device operates over a wide temperature range, with cryogenic conditions offering optimal switching steepness and noise performance for high-speed electronics, quantum sensing, and single-electron applications.
