Multilayered PdTe_(2)/thin Si heterostructures as self-powered flexible photodetectors with heart rate monitoring ability

Two-dimensional layered material/semiconductor heterostructures have emerged as a category of fascinating architectures for developing highly efficient and low-cost photodetection devices.Herein,we present the construction of a highly efficient flexible light detector operating in the visible-near infrared wavelength regime by integrating a PdTe2 multilayer on a thin Si film.A representative device achieves a good photoresponse performance at zero bias including a sizeable current on/off ratio exceeding 105,a decent responsivity of~343 mA/W,a respectable specific detectivity of~2.56×10^(12)Jones,and a rapid response time of 4.5/379μs,under 730 nm light irradiation.The detector also displays an outstanding long-term air stability and operational durability.In addition,thanks to the excellent flexibility,the device can retain its prominent photodetection performance at various bending radii of curvature and upon hundreds of bending tests.Furthermore,the large responsivity and rapid response speed endow the photodetector with the ability to accurately probe heart rate,suggesting a possible application in the area of flexible and wearable health monitoring.

Patterned growth ofβ-Ga_(2)O_(3) thin films for solar-blind deep-ultraviolet photodetectors array and optical imaging application

Solar-blind deep-ultraviolet(DUV)photodetectors based on Ga_(2)O_(3)have attracted great attention due to their potential applications for many military and civil purposes.However,the development of device integration for optoelectronic system applications remains a huge challenge.Herein,we report a facile method for patterned-growth of high-qualityβ-Ga_(2)O_(3)thin films,which are assembled into a photodetectors array comprising 8×8 device units.A representative detector exhibits outstanding photoresponse performance,in terms of an ultra-low dark current of 0.62 pA,a large Ilight/Idark ratio exceeding 10^(4),a high responsivity of 0.72 A W^(-1) and a decent specific detectivity of 4.18×10^(11)Jones,upon 265 nm DUV illumination.What is more,the DUV/visible(250/400 nm)rejection ratio is as high as 10^(3) with a sharp response cut-off wave length at 280 nm.Further optoelectronic analysis reveals that the photodetectors array has good uniformity and repeatability,endowing it the capability to serve as a reliable DUV light image sensor with a decent spatial resolution.These results suggest that the proposed technique offers an effective avenue for patterned growth ofβ-Ga_(2)O_(3)thin films for multifunctional DUV optoelectronic applications.

CTAB Assisted Synthesis of CuS Microcrystals:Synthesis,Mechanism,and Electrical Properties

CuS microcrystals were successfully prepared through a mild solvothermal reaction in ethylene glycol （EG） with the assistance of cationic surfactant cetyltrimethylammonium bromide （CTAB）. An interesting morphology evolution from flower-like microspheres to hollow microspheres, and finally to smooth nanoflakes was observed when increasing the amount of CTAB. The products were characterized by X-ray diffraction （XRD）, scanning electron microscopy （SEM）, transmission electron microscopy （TEM）, and UV-vis spectroscopy. It was found that the amount of CTAB played an important role in determining the morphology of the CuS microcrystals. Electrical measurement reveals that the as-prepared CuS microspheres were of high conductivity, which might favor their device applications. It is expected that CuS microcrystals with controlled morphologies and structures will have important applications in solar cells. This simple but effective method could also be extended to the controlled growth of other inorganic microcrystals.

Actively controllable terahertz switches with graphene-based nongroove gratings

We systematically investigated the tunable dynamic characteristics of a broadband surface plasmon polariton(SPP) wave on a silicon-graded grating structure in the range of 10–40 THz with the aid of single-layer graphene.The theoretical and numerical simulated results demonstrate that the SPPs at different frequencies within a broadband range can be trapped at different positions on the graphene surface, which can be used as a broadband spectrometer and optical switch. Meanwhile, the group velocity of the SPPs can be modulated to be several hundred times smaller than light velocity in vacuum. Based on the theoretical analyses, we have predicted the trapping positions and corresponding group velocities of the SPP waves with different frequencies. By appropriately tuning the gate voltages, the trapped SPP waves can be released to propagate along the surface of graphene or out of the graded grating zone. Thus, we have also investigated the switching characteristics of the slow light system, where the optical switching can be controlled as an "off" or "on" mode by actively adjusting the gate voltage. The slow light system offers advantages, including broadband operation, ultracompact footprint, and tunable ability simultaneously, which holds great promise for applications in optical switches.