A self-powered solar-blind UV-enhanced Bi_(2)Se_(3)/a-Ga_(2)O_(3)/p-Si heterojunction photodetector for full spectral photoresponse and imaging

Self-powered full-spectrum photodetectors(PDs)offer numerous advantages,such as broad application fields,high precision,efficiency,and multi-functionality,which represent a highly promising and potentially valuable class of detectors for future development.However,insensitive response to solar-blind ultraviolet(UV)and complex and expensive preparation processes greatly limit their performance and practical application.In this study,a self-powered full-spectrum Bi_(2)Se_(3)/a-Ga_(2)O_(3)/p-Si heterojunction PD with high sensitivity for solar-blind UV band prepared by a simple and low-cost two-step synthesis method is presented.Experiments results reveal that the developed PD has an excellent performance,such as high sensitivity from 200 to 850 nm,and a responsivity of 1.38 mA/W as well as a detectivity of 3.22×10^(10) Jones under 254 nm light at zero bias.Additionally,the unencapsulated device displays exceptional stability and imaging capabilities.It is expected that Bi_(2)Se_(3)/a-Ga_(2)O_(3)/p-Si heterojunction PD with a simple and low-cost synthesis method has great potential for self-powered full-spectrum photodetectors.

Confinement characteristic of primary electrons with the variation of channel width in the discharge chamber of annular ion thruster

In this paper,the confinement characteristic of primary electrons in the non-axisymmetric discharge chamber of annular ion thruster is investigated by a three-dimensional(3 D)non-self-consistent particle tracking model with Monte Carlo Collision(MCC)method.The results show that:The density of primary electrons upstream of ion optics on cathode axis is about 5–50 times higher than that of the other side,which means that the density of primary electrons is obviously non-axisymmetric.The channel width has a significant effect on the average density and uniformity of primary electrons.The average density can be increased by nearly 1.5 times under the appropriate channel width,meanwhile,the variance of density distribution can be reduced by more than 2 times.This is because that increasing the channel width can improve the average confinement length of primary electrons greatly.Furthermore,there is an infection point in the increase of primary electron average confinement length with the channel width,which caused by the significant change of magnetic field structure.Under the case after the inflection point,primary electron mainly(more than 50%)moves to the channel center,which makes the average confinement length of primary electrons and their number in the discharge chamber increase largely.

Plasma transport simulation under different conditions and optimization analysis of dual-stage grid ion thruster

In order to study the extraction and acceleration mechanism of the dual-stage grid,a three-dimensional model based on the Particle-In-Cell/Monte Carlo Collision(PIC/MCC)method is performed.Dual-stage grid ion thruster is a new type of electrostatic ion thruster,which can break through the limitations of traditional gridded ion thrusters,and greatly improve the specific impulse.The high performance also makes the grid sensitive to operating parameters.In this paper,the influence of grid parameters on xenon ion thruster’s performance in a wide range is systematically simulated,and the optimal operating condition is given.Both the over-focusing of the plume,and the transparency of the screen grid are improved,and the grid corrosion is reduced through simulation optimization.The specific impulse under the given working conditions is 9877.24 s and the thrust is 7.28 mN.Based on the simulation optimization,the limitation of the dual-stage grid is discussed.The grid performs well under high voltage conditions(>3000 V)but not well under low voltage conditions(<2000 V).Finally,since argon is cheaper and more advantageous in future engineering applications,the plasma distribution and grid extraction ability under xenon and argon are analyzed and compared to study the flexibility of the dual-stage grid ion thruster.The simulation results show that a set of optimal parameters is only applicable to the corresponding propellant,which needs to be optimized for different propellant types.

Surface engineering of highly ordered Bi_(2)S_(3)film with open channels toward high-performance broadband photodetection

The highly ordered film assembled by regularly 1D nanostructures has potentialprospects in electronic,photoelectronic and other fields because of its excellentlight-trapping effect and electronic transport property.However,the controlledgrowth of highly ordered film remains a great challenge.Herein,large-area andhighly ordered Bi_(2)S_(3)film is synthesized on fluorophlogopite mica substrate bychemical vapor deposition method.The Bi2S3 film features hollowed-outcrosslinked network structure,assembled by 1D nanobelts that regularly distributein three orientations,which agrees well with the first principles calculations.Based on the as-grown Bi_(2)S_(3)film,the broadband photodetector with a responserange from 365 to 940 nm is fabricated,exhibiting a maximum responsivity upto 98.51 mA W^(–1),specific detectivity of 2.03×10^(10)Jones and fast response timeof 35.19 ms.The stable instantaneous on/off behavior for 500 cycles and reliablephotoresponse characteristics of the Bi_(2)S_(3)photodetector after storage in air for6 months confirm its excellent long-term stability and air stability.Significantly,as sensing pixel and signal receiving terminal,the device successfully achieveshigh-resolution imaging of characters of“H”,“I”and“T”,and secure transmissionof confidential information.This work shows a great potential of the largeareaand highly ordered Bi_(2)S_(3)film toward the development of future multiplefunctional photoelectronic applications.