Yaping Dan

Low‐temperature infrared sensing requires temperature information to be extracted from weak thermal radiation while preserving optical throughput. Nanoimprinted metasurface filters combine multispectral encoding with neural‐network calibration to address this challenge. A single circular‐ring geometry controls passband position, bandwidth, and overlap, with simulated tuning across 6.4–11.2 μm. Deep‐ultraviolet stepper lithography and ultraviolet nanoimprinting transfer reusable master patterns to 1‐inch zinc sulfide filters. Four broad, partially overlapping bands retain peak transmittance near 80% and provide complementary spectral inputs for blackbody measurements from −20°C to 20°C. Neural‐network regression on the processed calibration curves achieves a mean absolute error of 0.160°C, compared with 0.434°C for one unfiltered input, a reduction of approximately 63%. Temperature‐resolved comparisons also identify lower errors at the cold end of the range. By connecting geometric spectral design, replicable fabrication, and computational temperature retrieval, this approach offers a route to compact multispectral thermometers that make better use of weak infrared signals.

The photoresponse of two-dimensional MoS2 photodetectors is often dominated by extrinsic effects, such as photoinduced Schottky barrier modulation and interfacial trap-induced photogating, which obscure the intrinsic material properties. To investigate the channel-dominated photoresponse of as-exfoliated few-layer MoS2, we fabricate suspended-channel phototransistors with bismuth-based Ohmic contacts to suppress major extrinsic effects from contacts and substrate interfaces. Through a direct comparison with conventional substrate-supported devices also with Ohmic contacts, we demonstrate that the suspended devices exhibit a fast response (45/83 μs rise/fall time) and a low-noise photocurrent consistent with a photoinduced narrowing of local depletion regions associated with defect states, described by a depletion-region modulation model originally developed for polycrystalline photoconductors. In contrast, conventional devices show orders-of-magnitude higher responsivity but suffer from slow, trap-dominated dynamics and significantly elevated noise. Parameter extraction from the photocurrent fitting reveals a minority carrier recombination lifetime of ∼2.03 ns in the suspended channel. This work clarifies the intrinsic photoresponse mechanism of MoS2 and underscores the critical role of interface engineering in realizing high-speed, low-noise photodetectors based on two-dimensional semiconductors.

Defects play an essential role in determining the resistive switching behavior, variability, and scalability of hBN-based memristors. In this work, we employ Ar+ implantation to create atomic defects within an array of Au/hBN/Au sandwich structures. As the Ar+ implantation dose increases from 0 to 4 × 1011 cm−2, the yield of Au/hBN/Au memristors linearly increases from 1.4% to 77%. Lateral force microscopy indicates that atomic-scale defects are created in the pristine hBN flakes by Ar+ ion implantation. High-resolution transmission electron microscopy shows that atomic-scale defect channels exist in the hBN flake with a memristive switching behavior. It is evident that conduction via these atomic-scale defect channels enables memristive behavior in Au/hBN/Au sandwich structures.

Phosphorus quantum dots (QDs) in silicon are a prominent candidate for semiconductor quantum computing based on donor spins. In this work, we report the formation of degenerate phosphorus QDs with a radius of 3 nm confined in a two-dimensional plane in silicon. A multilayer of SiO2/POx/SiO2 on Si substrate is first deposited by atomic layer deposition, which serves as the capping layer, doping source, and doping mask. Defective channels in the SiO2 doping mask layer are then created by random argon (Ar) ion implantation. Finally, phosphorus dopants from the doping source layer, driven by pulsed laser annealing, diffuse through the defective channels in SiO2 into Si substrate, forming phosphorus QDs confined in a two-dimensional (2D) plane near the Si surface. By reducing the Ar dose, we observe a sharp metal-to-insulator transition (MIT) in the resulting 2D electron system. Based on the MIT model for quantum dots, we find that each Ar ion implantation has a chance of only 6.4%–8.1% to create a phosphorus quantum dot.

Two‐dimensional materials show promise in post‐Moore electronics but face challenges in damage‐free conformal transfer onto nanostructures. Here, we propose a conformal transfer strategy based on a poly (propylene carbonate) support layer with a low glass transition temperature. Through the synergistic regulation of temperature and stress, large‐area monolayer MoS ₂ achieves damage‐free conformal coverage of silicon nanowire (SiNW). The coverage height can reach up to 300 times the thickness of the nanowires themselves, far exceeding the geometric adaptation limits of conventional methods. By adjusting the aspect ratio of the SiNW, a spontaneous air gap is formed between the MoS ₂ gate electrode and the side wall of nanowire. This air gap acts as a layer with an ultra‐low dielectric constant, thereby restructuring the gate‐channel electrostatic boundary conditions. This MoS ₂ /Si nanowire dual‐mechanism transistor exhibits excellent electrical performance, featuring a subthreshold swing as low as 63.95 mV dec ⁻¹ . These results unveil the application potential of hybrid‐dimensional optoelectronic devices in compact transistor preamplifiers and logic device technology.

This article presents a comprehensive analytical theory for the avalanche breakdown process in p-n junction diodes to address the critical reliance on empirical models in the design of avalanche photodiodes (APDs) and single-photon avalanche diodes (SPADs). The proposed model is derived from fundamental carrier continuity equations and impact excitation probability. Eventually, it yields closed-form expressions for the avalanche current density and the breakdown voltage. It demonstrates excellent agreement with experimental current–voltage characteristics across various semiconductors (Si, GaN, 4H-SiC, and InP) and a wide temperature range. TCAD simulations are also adopted to validate this model. The theory establishes a unified, physics-based criterion for defining the avalanche breakdown voltage, revealing its functional dependence on material parameters (bandgap, dielectric constant, and mean-free path) and doping concentrations. Significantly, it explicitly predicts the theoretical minimum and maximum limits for the breakdown voltage in a given material, which were well known but only implicitly reflected in previous empirical models. This work provides a rigorous theoretical framework for the steady-state dark avalanche current for the targeted design of diverse avalanche-based devices, ranging from low-breakdown-voltage SPADs for integrated quantum photonics to high-breakdown-voltage power devices, moving beyond trial-and-error approaches.

Er-implanted Si (Er:Si) is a promising candidate for scalable planar quantum memory (QM) applications. In Er:Si, Er has a preference to coordinate with O impurities, and multiple types of Er center are typically formed after a post-implant anneal. Intrinsic Si was implanted with 10 ¹⁸ cm ⁻³ Er, then annealed using a rapid quench annealing technique at 950°C for 10 min with quench rates of 5°C, 23°C, 46°C, 93°C, 185°C, and 400°C/s. The evolution of photoluminescence (PL) peaks and their associated Er centers was tracked as a function of quench rate. Across all samples, five distinct Er centers were identified. Two centers, one with mixed Si/O coordination and one with Si-only coordination, exhibited fully resolved crystal-field splitting of the ⁴ I _15/2 ground state together with 2–3 hot lines from the ⁴ I _13/2 excited state; fitting crystal-field parameters for both was consistent with C _2v symmetry. The mixed Si/O coordinated center was suppressed at quench rates above 185°C/s, while the Si-only coordinated center was progressively enhanced with increasing quench rate up to the maximum of 400°C/s. These results indicate that rapid quench annealing can favor the formation of Si-coordinated Er centers in Er:Si, which is required for QM applications.