Piezo-Acoustic Resistive Switching Behaviors in High-Performance Organic-Inorganic Hybrid Perovskite Memristors.

Memristors are regarded as promising candidates for breaking the problems including high off-chip memory access delays and the hash rate cost of frequent data moving induced by algorithms for data-intensive applications of existing computational systems. Recently, organic-inorganic halide perovskites (OIHPs) have been recognized as exceptionally favorable materials for memristors due to ease of preparation, excellent electrical conductivity, and structural flexibility. However, research on OIHP-based memristors focuses on modulating resistive switching (RS) performance through electric fields, resulting in difficulties in moving away from complex external circuits and wire connections. Here, a multilayer memristor has been constructed with eutectic gallium and indium (EGaIn)/ MAPbI3 /poly(3,4-ethylenedioxythiophene): poly(4-styrenesulphonate) (PEDOT: PSS)/indium tin oxide (ITO) structure, which exhibits reproducible and reliable bipolar RS with low SET/RESET voltages, stable endurance, ultrahigh average ON/OFF ratio, and excellent retention. Importantly, based on ion migration activated by sound-driven piezoelectric effects, the device exhibits a stable acoustic response with an average ON/OFF ratio greater than 103 , thus realizing non-contact, multi-signal, and far-field control in RS modulation. This study provides a single-structure multifunctional memristor as an integrated architecture for sensing, data storage, and computing.

Growth and High-Performance Photodetectors of CsPbBr3 Single Crystals.

Organic-inorganic hybrid perovskites have demonstrated exceptional photovoltaic properties, making them highly promising for solar cells and photodetectors (PDs). However, the organic components of these materials are vulnerable to heat and strong light illumination, limiting their application prospects. All-inorganic cesium-based perovskite PDs, on the other hand, possess enhanced thermal tolerance and stability, making them ideal for perovskite applications. The utilization of a ternary mixture solvent and additives in combination with single crystal (SC) growth has enabled the production of highly crystalline SCs with a defect density of 3.79 × 109 cm-3. The performance of the SC PDs had been evaluated using metal-semiconductor-metal devices, which demonstrated excellent results with a dark current as low as 0.198 µA at 10 V bias, on-off ratios exceeding 103, and a response time of shorter than 1 ms.

Simulation on a dispersion-managed 4H-SiC on insulator waveguide for infrared supercontinuum generation.

We demonstrate infrared supercontinuum generation in 4H-SiC on insulator slab waveguides. The effect of waveguide geometry parameters on dispersion is investigated to switch the zero-dispersion wavelength close to the pump wavelength. The 1 cm long 4H-SiC waveguide is pumped by 100 fs pulses at 1550 nm with 2000 W peak power, and the generated supercontinuum extends from ∼1000 to ∼3560n m (at 20 dB level). This work shows that 4H-SiC has significant potential as on-chip photonic sources for spectroscopic applications in infrared wavelengths.

High Temperature CsPbBrxI3-x Memristors Based on Hybrid Electrical and Optical Resistive Switching Effects.

The emergence of perovskite-based memristors associated with the migration of ions has attracted attention for use in overcoming the limitations of the von Neumann computing architecture and removing the bottleneck of storage density. However, systematic research on the temperature dependence of halide perovskite-based memristors is still required due to the unavoidable thermal stability limits. In this work, mixed halide CsPbBrxI3-x-based (X = 0, 1, 2) memristors with unique electrical and optical resistive switching properties in an ambient atmosphere from room temperature to a 240 °C maximum have been successfully achieved. At room temperature, the CsPbBrxI3-x-based memristors exhibit outstanding resistive switching behaviors such as ultralow operating voltage (∼0.81, ∼0.64, and ∼0.54 V for different devices, respectively), moderate ON/OFF ratio (∼102), stable endurance (103 cycles), and long retention time (104 s). The CsPbBrxI3-x-based memristors maintain excellent repeatability and stability at high temperature. Endurance failures of CsPbI3, CsPbBrI2, and CsPbBr2I memristors occur at 90, 150, and 270 °C, respectively. Finally, nonvolatile imaging employing CsPbBr2I-based memristor arrays based on the electrical-write and optical-erase operation at 100 °C has been demonstrated. This study provides utilization potentiality in the high temperature scenarios for perovskite wearable and large-scale information devices.

Miniature resonator sensor based on a hybrid plasmonic nanoring.

A miniature resonator sensor based on a hybrid plasmonic nanoring with a gold layer coated uniformly on the outer boundary is described and investigated. By using the Lumerical finite-difference-time-domain (FDTD) method, the optimized sizes of the plasmonic layer thickness and the central hole are given and insight into the dependence of spectral displacements, Q factors, sensitivity and detection limits on the ambient refractive index is presented. Simulation results reveal that the miniature resonator sensor featuring high sensitivity of 339.8 nm/RIU can be realized. The highest Q factor can reach ∼60,000 with this nanoring and the minimum detection limit is as low as 1.5 × 10-4 RIU. The effects on the resonance shifts and Q factors due to geometric shapes of the inner boundary of the nanoring are discussed as well. This miniature resonator sensor has good potential for highly sensitive ultracompact sensing applications.

Enhanced Performance of a Visible Light Detector Made with Quasi-Free-Standing Graphene on SiC.

The excellent optoelectronic properties of graphene give it great potential for applications in optical detection. Among the graphenes obtained through many synthetic methods, epitaxial graphene obtained by thermal decomposition on silicon carbide has remarkable advantages for preparing photodetectors. In this research, epitaxial graphene has been successfully prepared on a silicon surface (0001) of semi-insulating 4H-SiC substrate with a size of 10 mm × 10 mm and epitaxial graphene has been converted to quasi-free-standing graphene by hydrogen passivation. Two metal-graphene-metal photodetectors were fabricated using the two types of graphenes above and the photo-absorption properties of detectors have been investigated under 650-nm laser illumination with different illumination powers. From a comparison of the performances between the two detectors, it was found that a photodetector fabricated with quasi-free-standing graphene shows enhanced performance under a light power of 0.018 mW. Responsivity and external quantum efficiency reach maxima of 5.11 A/W and 9.74%, respectively. This dramatic improvement is mainly due to the disappearance of the buffer layer in epitaxial graphene, providing a new method to achieve optimization of graphene-based opto-electrical devices.

Enhanced Optoelectronic Performance on the (110) Lattice Plane of an MAPbBr3 Single Crystal.

Hybrid organic-inorganic lead halide perovskites have attracted significant attention due to their impressive optoelectronic properties. MAPbX3 (MA= CH3NH3+, X= Cl, Br or I), the most popular member of this family, has been recognized as an important next-generation optoelectronic materials contender, and remarkable progress has been achieved in both thin films and single crystals. However, the lack of optimizations in energy harvest, transportation, carrier extraction, and process compatibility is hindering their future development. In this study, a triangle prism MAPbBr3 single crystal exposing (100) and (110) crystallographic planes was successfully synthesized, and the optoelectronic performances of these two lattice planes were systematically explored by employing a planar metal-semiconductor-metal (MSM) device. Compared to the device fabricated on the (100) plane, a 153.33% enhancement of responsivity was achieved under 10 µW irradiation and 10 V bias on the (110) plane. Finally, possible mechanism for such an enhancement was discussed based on the different defect migration behaviors of (100) and (110) planes.

Surface plasmon enhanced photochemical etching of p-type GaP: a direct demonstration of wavelength selectivity.

We report here on significant enhancement of the photochemical etching of p-type gallium phosphide (GaP) by Au plasmonic nanostructures. The photochemical etching rate of defect (dislocation) states of Au-coated p-GaP samples is ten times higher than blank samples when irradiated with 532 nm laser. It is confirmed that the enhancement of photochemical etching is wavelength selective. Only 532 nm laser can efficiently increase the photochemical etching rate, while lasers of other wavelengths (375, 405, 445, and 473 nm) show limited or negative effects. This observation can be attributed to defect (dislocation) enhanced photochemical etching through localized surface plasmon resonance of Au nanostructures. This method may open a new pathway for controlled fabrication of novel optoelectronic devices.