This study proposes an innovative design strategy for molybdenum disulfide (MoS₂) optoelectronic devices based on three-dimensional folded configurations. A “Z”-shaped folded MoS₂ device was fabricated through mechanical exfoliation combined with a pre-strain technique on elastic substrates. Experimental investigations reveal that the geometric folding deformation induces novel photocurrent response zones near folded regions beyond the Schottky junction area via band structure reconstruction, achieving triple polarity switching (negative–positive–negative–positive) of photocurrent. This breakthrough overcomes the single-polarity separation mechanism limitation in conventional planar devices. Scanning photocurrent microscopy demonstrates a 40-fold enhancement in photocurrent intensity at folded regions compared to flat areas, attributed to the optimization of carrier separation efficiency through a pn junction-like built-in electric field induced by the three-dimensional configuration. Voltage-modulation experiments show that negative bias (−150 mV) expands positive response regions, while +200 mV bias induces a global negative response, revealing a dynamic synergy between folding deformation and electric field regulation. Theoretical analysis identifies that the band bending and built-in electric field in folded regions constitutes the physical origin of multiple polarity reversals. This work establishes a design paradigm integrating “geometric deformation-band engineering” for regulating optoelectronic properties of two-dimensional materials, demonstrating significant application potential in programmable photoelectric sensing and neuromorphic devices.

Phase engineering of two-dimensional transition metal dichalcogenides enables precise modulation of their electronic properties and holds great promise for next-generation electronic devices. However, achieving spatially controlled and reversible phase transitions reliably remains a key challenge for practical applications. Here, we demonstrate a localized and controllable phase transition from the semiconducting 2H to the metallic 1T′ phase in MoTe2 via laser irradiation. This transition, confirmed by Raman spectroscopy and atomic force microscopy, leads to a remarkable increase in conductivity, with the current response enhanced by up to three orders of magnitude. Furthermore, we reveal that the laser-induced 1T′ phase exhibits spontaneous reversion to the original 2H phase over time when stored under vacuum, accompanied by a corresponding decay in electrical conductance. This reversible and tunable phase-switching behavior highlights the potential of laser-controlled phase patterning for applications in reconfigurable electronics, particularly in memristive devices. Our work not only establishes a method for spatially defined phase engineering but also provides critical insights into the dynamics of phase stability, offering a foundation for the design of future controllable phase-change systems.

In the experiment, it has been observed that the resistivity of palladium (Pd) is sensitively reduced by the absorption of hydrogen, and the detection of hydrogen has been achieved by this principle. However, the realization of the detection only relies on the calibration of the resistivity and the hydrogen concentration of the specific detection model and lacks theoretical analysis. Based on the Density functional theory calculations, the structural, thermodynamic and electronic properties and conductivity of hydrogen atoms adsorbed on the Pd (111) surface at different concentrations were studied in a rare hydrogen environment (1%). The calculation results show that the adsorption mode of hydrogen atoms on the fcc site is the most stable. The differential charge density analysis shows that the interaction between hydrogen atoms and the metal surface increases with the increase of the number of hydrogen atoms, which can be confirmed by the calculation of the electron locality function (ELF) of the system. The DOS analysis shows that the electron number density near the Fermi level of the Pd-H system is 0.521% 0.403% and 0.333% lower than that of the Pd layer respectively. We find that the electron number density near the Fermi level determines the conductance change of the Pd-H system under rare hydrogen conditions.

This study systematically investigates the effects of trap concentration on self-heating and terahertz (THz) responses in GaN HEMTs using Sentaurus TCAD. Traps, inherently unavoidable in semiconductors, can be strategically introduced to engineer specific energy levels that establish competitive dynamics between the electron momentum relaxation time and the carrier lifetime. A simulation-based exploration of this mechanism provides significant scientific value for enhancing device performance through self-heating mitigation and THz response optimization. An AlGaN/GaN heterojunction HEMT model was established, with trap concentrations ranging from 0 to $5\times {10}^{17} {\mathrm{c}\mathrm{m}}^{-3}$. The analysis reveals that traps significantly enhance channel current (achieving 3× gain at $1\times 10^{17} {\mathrm{c}\mathrm{m}}^{-3}$) via new energy levels that prolong carrier lifetime. However, elevated trap concentrations (>$1\times {10}^{16} {\mathrm{c}\mathrm{m}}^{-3}$) exacerbate self-heating-induced current collapse, reducing the min-to-max current ratio to 0.9158. In THz response characterization, devices exhibit a distinct DC component (${\mathrm{U}}_{\mathrm{d}\mathrm{c}}$) under non-resonant detection ($\mathsf{\omega }\mathsf{\tau }\ll 1$). At a trap concentration of $1\times {10}^{15} {\mathrm{c}\mathrm{m}}^{-3}$, ${\mathrm{U}}_{\mathrm{d}\mathrm{c}}$ peaks at $0.12 \mathrm{V}$ when ${\mathrm{V}}_{\mathrm{g}}\mathrm{D}\mathrm{C}=-7.8 \mathrm{V}$. Compared to trap-free devices, a maximum response attenuation of 64.89% occurs at ${\mathrm{V}}_{\mathrm{g}}\mathrm{D}\mathrm{C}=-4.9 \mathrm{V}$. Furthermore, ${\mathrm{U}}_{\mathrm{d}\mathrm{c}}$ demonstrates non-monotonic behavior with concentration, showing local maxima at $4\times {10}^{15} {\mathrm{c}\mathrm{m}}^{-3}$ and $7\times {10}^{15} {\mathrm{c}\mathrm{m}}^{-3}$, attributed to plasma wave damping and temperature-gradient-induced electric field variations. This research establishes trap engineering guidelines for GaN HEMTs: a concentration of $4\times {10}^{15} {\mathrm{c}\mathrm{m}}^{-3}$ optimally enhances conductivity while minimizing adverse impacts on both self-heating and the THz response, making it particularly suitable for high-sensitivity terahertz detectors.