8-nm narrowband photodetection in diamonds

Spectrally-selective photodetection plays a crucial role in various applications,including target imaging and environmental monitoring.Traditional deep-ultraviolet(DUV)narrowband photodetection systems consist of broadband photodetectors and filters,which complicates the architecture and constrains imaging quality.Here,we introduce an electronic-grade diamond single-crystal photodetector exhibiting an exceptionally narrow spectral response in the DUV range with a full width at half maximum of 8 nm.By examining diamond photodetectors with varying dislocation densities,we propose that mitigating the defect-induced trapping effect to achieve charge collection narrowing,assisted by free exciton radiative recombination,is an effective strategy for narrowband photodetection.The superior performance of this device is evidenced through the imaging of DUV light sources,showcasing its capability to differentiate between distinct light sources and monitor human-safe sterilization systems.Our findings underscore the promising potential applications of electronicgrade diamond in narrowband photodetection and offer a valuable technique for identifying electronic-grade diamond.

InSe-Te van der Waals heterostructures for current rectification and photodetection

As the basis of modern electronics and optoelectronics,high-performance,multi-functional p-n junctions have manifested and occupied an important position.However,the performance of the silicon-based p-n junctions declines gradually as the thickness approaches to few nanometers.The heterojunction constructed by two-dimensional(2D)materials can significantly improve the device performance compared with traditional technologies.Here,we report the In Se-Te type-II van der Waals heterostructures with rectification ratio up to 1.56×10^(7) at drain-source voltage of±2 V.The p-n junction exhibits a photovoltaic and photoelectric effect under different laser wavelengths and densities and has high photoresponsivity and detectivity under low irradiated light power.Moreover,the heterojunction has stable photo/dark current states and good photoelectric switching characteristics.Such high-performance heterostructured device based on 2D materials provides a new way for futural electronic and optoelectronic devices.

Surface plasmon enhanced infrared photodetection

Infrared photodetectors have been used extensively in biomedicine, surveillance, communication and astronomy. However, state of the art technology based on III-V and II-VI compounds still lacks excellent performance for high-temperature operation. Surface plasmon polaritons (SPPs) have demonstrated their capability in improving the light detection from visible to infrared wave range due to their light confinement in subwavelength scale. Advanced fabrication techniques such as electron-beam lithography (EBL) and focused ion-beam (FIB), and commercially available numerical design tool like Finite-Difference Time-Domain (FDTD) have enabled rapid development of surface plasmon (SP) enhanced photodetectors. In this review article, the basic mechanisms behind the SP-enhanced photodetection, the different type of plasmonic nanostructures utilized for enhancement, and the reported SP-enhanced infrared photodetectors will be discussed.

Fast-speed self-powered PEDOT:PSS/α-Ga_(2)O_(3)nanorod array/FTO photodetector with solar-blind UV/visible dual-band photodetection

Theα-Ga2 O_(3)nanorod array is grown on FTO by hydrothermal and annealing processes.And a self-powered PEDOT:PSS/α-Ga_(2)O_(3)nanorod array/FTO(PGF)photodetector has been demonstrated by spin coating PEDOT:PSS on theα-Ga_(2)O_(3)nanorod array.Successfully,the PGF photodetector shows solar-blind UV/visible dual-band photodetection.Our device possesses comparable solar-blind UV responsivity(0.18 mA/W at 235 nm)and much faster response speed(0.102 s)than most of the reported self-poweredα-Ga_(2)O_(3)nanorod array solar-blind UV photodetectors.And it presents the featured and distinguished visible band photoresponse with a response speed of 0.136 s at 540 nm.The response time is also much faster than the other non-self-poweredβ-Ga_(2)O_(3)DUV/visible dual-band photodetectors due to the fast-speed separation of photogenerated carries by the built-in electric field in the depletion regions of PEDOT:PSS/α-Ga_(2)O_(3)heterojunction.The results herein may prove a promising way to realize fast-speed self-poweredα-Ga_(2)O_(3)photodetectors with solar-blind UV/visible dual-band photodetection by simple processes for the applications of multiple-target tracking,imaging,machine vision and communication.

New approach for deriving density operator for describing continuum photodetection process

By introducing the two-mode entangled state representation 〈η｜ whose one mode is a fictitious one accompanying the system mode, this paper presents a new approach for deriving density operator for describing continuum photodetection process.

Realization of stimulated emission-based detector and its application to antinormally ordered photodetection

Using a stimulated parametric down-conversion process combined with a conventional detector, we theoretically propose a scheme to realize the stimulated emission-based detector, and investigate the antinormalty ordered correlation function and Fano factor for the coherent field based on it. Such a detection has advantages over the normally ordered one especially when the intensity of the field is weak.

In situ construction of PtSe_(2)/Ge Schottky junction array with interface passivation for broadband infrared photodetection and imaging

Infrared(IR)detection is vital for various military and civilian applications.Recent research has highlighted the potential of two-dimensional(2D)topological semimetals in IR detection due to their distinctive advantages,including van der Waals(vdW)stacking,gapless electronic structure,and Van Hove singularities in the electronic density of states.However,challenges such as large-scale patterning,poor photoresponsivity,and high dark current of photodetectors based on 2D topological semimetals significantly impede their wider applications in low-energy photon sensing.Here,we demonstrate the in situ fabrication of PtSe_(2)/Ge Schottky junction by directly depositing 2D PtSe_(2) films with a vertical layer structure on a Ge substrate with an ultrathin AlOx layer.Due to high quality junction,the photodetector features a broadband response of up to 4.6μm,along with a high specific detectivity of�1012 Jones,and operates with remarkable stability in ambient conditions as well.Moreover,the highly integrated device arrays based on PtSe_(2)/AlOx/Ge Schottky junction showcases excellent Mid-IR(MIR)imaging capability at room temperature.These findings highlight the promising prospects of 2D topological semimetals for uncooled IR photodetection and imaging applications.

Polymer: Non-fullerene acceptor heterojunction-based phototransistor for short-wave infrared photodetection

It remains full of challenge for extending short-wave infrared(SWIR)spectral response and weak-light detection in the context of broad spectral responses for phototransistor.In this work,a novel poly(2,5-bis(4-hexyldodecyl)-2,5-dihydro-3,6-di-2-thienyl-pyrrolo[3,4-c]pyrrole-1,4-dione-alt-thiophene)(PDPPT3-HDO):COTIC-4F organic bulk-heterojunction is prepared as active layer for bulk heterojunction phototransistors.PDPPT3-HDO serves as a hole transport material,while COTIC-4F enhances the absorption of SWIR light to 1020 nm.As a result,smooth and connected PDPPT3-HDO film is fabricated by blade coating method and exhibits high hole mobility up to 2.34 cm^(2)·V^(-1)·s^(-1) with a current on/off ratio of 4.72×10^(5) in organic thin film transistors.PDPPT3-HDO:COTIC-4F heterojunction phototransistors exhibit high responsivity of 2680 A·W^(-1) to 900 nm and 815 A·W^(-1) to 1020 nm,with fast response time(rise time~20 ms and fall time~100 ms).The photosensitivity of the heterojunction phototransistor improves as the mass ratio of non-fullerene acceptors increases,resulting in an approximately two orders of magnitude enhancement compared to the bare polymer phototransistor.Importantly,the phototransistor exhibits decent responsivity even under ultra-weak light power of 43μW·cm^(-2) to 1020 nm.This work represents a highly effective and general strategy for fabricating efficient and sensitive SWIR light photodetectors.

Evaluating the quantum confinement effects modulating exciton and electronic band structures of two-dimensional layered MoSSe films and their photodetection potentials

Emerging two-dimensional ternary transition metal dichalcogenide alloys have attracted much attention for their unique optical and optoelectronic properties,making them ideal candidates for optoelectronic applications.However,a comprehensive understanding of their quantum confinement effects and photoelectronic response characteristics remains crucial for device optimization and performance enhancement.In this study,we employed various spectroscopic techniques to investigate the optical properties and electronic band structures of molybdenum sulfide selenide(MoSSe)films with different layer numbers(4–11 layers).Our results revealed the splitting of Raman modes and shifting of phonon vibrational frequencies with increasing thickness,suggesting that MoSSe has strong interactions within the lattice.The A1g and E2g 1 modes were mainly shifted by internal strain and dielectric screening effect versus thickness,respectively.The redshift phenomenon of A and B excitons with increasing thickness was attributed to the leading effect of quantum confinement on exciton properties and optical band gaps.We observed a strong decrease in the direct bandgap spectral weight in photoluminescence(PL)when the layer number increased from 4 to 5.In addition,we have fabricated MoSSe photodetectors that exhibit a broadband response in the visible wavelength band of 350–800 nm.Furthermore,the observed enhancement in photocurrent and responsivity with increasing film thickness underscored the potential of MoSSebased devices for practical optoelectronic applications.This research contributes to advancing our fundamental understanding of MoSSe materials and paves the way for the design and development of high-performance optoelectronic devices.

Anomalous magnetic property and broadband photodetection in ultrathin non-layered manganese selenide semiconductor

Two-dimensional(2D)semiconductors with intrinsic ferromagnetism are highly desirable for potential applications in nextgeneration spintronic and optoelectronic devices.However,controllable synthesis of intrinsic 2D magnetic semiconductor on a substrate is still a challenging task.Herein,large-area 2D non-layered rock salt(α-phase)MnSe nanosheets were grown on mica substrates,with the thickness changing from 54.2 to 0.9 nm(one unit cell),by chemical vapour deposition.The X-ray diffraction,Raman spectroscopy,transmission electron microscopy,and X-ray photoelectron spectroscopy measurements confirmed that the resulting 2Dα-MnSe nanosheets were obtained as high-quality single crystals.The magnetic hysteresis loops and synchrotron X-ray measurements directly indicated the anomalous magnetic properties inα-MnSe nanosheets.Comprehensive analysis of the reasons for magnetic property revealed that the low-temperature phase transition,small number of stacking differences in crystals,and surface weak oxidation in(111)-orientedα-MnSe were the main mechanisms.Furthermore,α-MnSe nanosheets exhibited broadband photoresponse from 457 to 671 nm with an outstanding detectivity and responsivity behaviours.This study presents the detailed growth process of ultrathin 2D magnetic semiconductorα-MnSe,and its outstanding magnetic properties and broadband photodetection,which provide an excellent platform for magneto-optical and magneto-optoelectronic research.

On-chip integrated GeSe_(2)/Si vdW heterojunction for ultravioletenhanced broadband photodetection,imaging,and secure optical communication

Broadband photodetection,spanning from ultraviolet(UV)to infrared(IR),is pivotal in diverse technological domains including astronomy,remote sensing,environmental monitoring,and medical diagnostics.However,current commercially available broadband photodetectors,predominately based on conventional narrow-bandgap semiconductors,exhibit limited sensitivity in the UV region.This limitation,stemming from the significant energy disparity between the semiconductor bandgap and UV photon,narrows their application scope.Herein,we report an innovative approach involving the in-situ van der Waals(vdW)integration of two-dimensional(2D)GeSe_(2)layers onto a Si substrate.This process yields a high-quality GeSe_(2)/Si vdW heterojunction device,which features a broad response range covering from UV to near-IR(NIR)with a greatly-enhanced sensitivity in the UV region.The device possesses high responsivities of 325 and 533.4 mA/W,large detectivities of 1.24×10^(13)and 2.57×10^(13)Jones,and fast response speeds of 20.6/82.1 and 17.7/81.0μs under 360 and 980 nm,respectively.Notably,the broadband image sensing and secure invisible optical communication capabilities of the GeSe_(2)/Si heterojunction device are demonstrated.Our work provides a viable approach for UV-enhanced broadband photodetection technology,opening up new possibilities and applications across various scientific and technological domains.

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.

Wafer-scale patterned growth of type-II Dirac semimetal platinum ditelluride for sensitive room-temperature terahertz photodetection

As the lastly unexplored electromagnetic wave,terahertz(THz)radiation has been exploited in a plenty of contexts such as fundamental research,military and civil fields.Most recently,representative two-dimensional(2D)topological semimetal,platinum ditelluride(PtTe_(2))has attracted considerable research interest in THz detection due to its unique physical properties.However,to achieve practical applications,the low-cost,large-scale,controllable synthesis and efficient patterning of 2D materials are key requirements,which remain a challenge for PtTe_(2)and its photodetectors(PDs).Herein,a facile approach is developed to obtain waferscale(2-inches)patterned PtTe_(2)arrays using one-step tellurium-vapor transformation method and micro-Nano technology.PtTe_(2)PD arrays are fabricated with the as-grown PtTe_(2)arrays evenly distributed on a 2-inch wafer,exhibiting high conductivity(~2.7×105 S m^(-1))and good electrical consistency.Driven by the Dirac fermions,PtTe_(2)PDs achieve a broadband(0.02-0.3 THz)response with a fast response speed(~4.7μs),a high sensitivity(~47 pW Hz^(-1/2))and high-resolution transmission THz-imaging capability,which displays the potential of large-area THz array imaging.These results are one step towards the practical applications of integrated PD arrays based on 2D materials.

Ga/GaSb nanostructures:Solution-phase growth for highperformance infrared photodetection

Gallium antimonide(GaSb)-based nanostructures have been reported via various vapor-phase synthetic routes while there is not a report on the growth of GaSb nanostructures via a complete one-step solution-phase synthetic strategy.Herein we report the design and synthesis of tadpole-like Ga/GaSb nanostructures by a one-step solution-phase synthetic route typically from the precursors of commercial triphenyl antimony(Sb(Ph)_(3))and trimethylaminogallium(Ga(NMe_(2))_(3))at 260°C in 1-octadecene.The GaSb nanocrystals are grown based on a solution–liquid–solid(SLS)mechanism with zinc blende phase,and their size and shape can be controlled in the procedures via manipulating the reaction conditions.Meanwhile,the tadpole-like Ga/GaSb nanostructures can be applied for the fabrication of a GaSb/Si nanostructured heterojunction-like photodetector over silicon wafer,which demonstrates excellent photoresponse and detection performances from wavelength of 405 to 1,064 nm with high photoresponding rate.Typically,the photodetector exhibits a high responsivity of 18.9 A·W^(−1),a superior detectivity of 1.1×10^(13)Jones,and an ultrafast response speed of 44 ns.The present work provides a new strategy to group III–V antimonide-based semiconducting nanostructures that are capable for the fabrication of photodetector with broadband,high-detectivity,and high-speed photodetecting performances.

Enhancement of silicon sub‑bandgap photodetection by helium‑ion implantation

Silicon sub-bandgap photodetectors can detect light at the infrared telecommunication wavelengths but with relatively weak photo-response.In this work,we demonstrate the enhancement of sub-bandgap photodetection in silicon by helium-ion implantation,without afecting the transparency that is an important benefcial feature of this type of photodetectors.With an implantation dose of 1×10^(13)ions/cm^(2),the minimal detectable optical power can be improved from−33.2 to−63.1 dBm,or,by 29.9 dB,at the wavelength of 1550 nm,and the photo-response at the same optical power(−10 dBm)can be enhanced by approximately 18.8 dB.Our work provides a method for strategically modifying the intrinsic trade-of between transparency and strong photo-responses of this type of photodetectors.

Photo-driven fin field-effect transistors

The integration between infrared detection and modern microelectronics offers unique opportunities for compact and high-resolution infrared imaging.However,silicon,the cornerstone of modern microelectronics,can only detect light within a limited wavelength range(<1100 nm)due to its bandgap of 1.12 eV,which restricts its utility in the infrared detection realm.Herein,a photo-driven fin field-effect transistor is presented,which breaks the spectral response constraint of conventional silicon detectors while achieving sensitive infrared detection.This device comprises a fin-shaped silicon channel for charge transport and a lead sulfide film for infrared light harvesting.The lead sulfide film wraps the silicon channel to form a“three-dimensional”infrared-sensitive gate,enabling the photovoltage generated at the lead sulfide-silicon junction to effectively modulate the channel conductance.At room temperature,this device realizes a broadband photodetection from visible(635 nm)to short-wave infrared regions(2700 nm),surpassing the working range of the regular indium gallium arsenide and germanium detectors.Furthermore,it exhibits low equivalent noise powers of 3.2×10^(-12) W·Hz^(-1/2) and 2.3×10^(-11) W·Hz^(-1/2) under 1550 nm and 2700 nm illumination,respectively.These results highlight the significant potential of photo-driven fin field-effect transistors in advancing uncooled silicon-based infrared detection.

Enhancement of MoTe2 near-infrared absorption with gold hollow nanorods for photodetection

Infrared(IR)light photodetection based on two dimensional(2D)materials of proper bandgap has attracted increasing attention.However,the weak IR absorption in 2D materials,due to their ultrathin attribute and indirect bandgap in multilayer structures,degrades their performance when used as IR photodetectors.In this work,we utilize the fact that few-layer MoTe2 flake has a near-IR(NIR)bandgap and demonstrate a^60-fold enhancement of NIR response by introducing a gold hollow nanorods on the surface.Such gold hollow nanorods have distinct absorption peak located also at the NIR regime,therefore induces strong resonance,benefitting NIR absorption in MoTe2,resulting in strong near-field enhancement.With the evidence from steady and transient state optical spectra,we confirm that the enhancement of NIR response originates only photon absorption,rather than electron transport at interfaces as observed in other heterostructures,therefore,precluding the requirement of high-quality interfaces for commercial applications.

Thickness-dependent highly sensitive photodetection behavior of lead-free all-inorganic CsSnBr_(3) nanoplates

Non-layered two-dimensional(2D) lead-free all-inorganic perovskites nanoplates have recently attracted considerable attention in photodetectors;however, the indepth investigation of thickness on photodetection performance is still lacking. In this work, by constructing the famous metal-semiconductor-metal photodetectors, the photodetection behaviors of thickness-controlled CsSnBr;nanoplates are investigated systematically. Ni electrodes are adopted for ensuring the good ohmic contact behaviors of as-fabricated photodetectors. With the increase in thickness, the photodetection performances improve accordingly, such as photocurrent increases from 0.22 to 19.40 nA, responsivity increases from 72.9 to 4893.7 mA·W^(-1), rise/decay time decreases from 11/35 to 3/10 ms, respectively. Notability, the dark current also increases with the increase in thickness, making the further investigation on the reduction in dark current meaningful.All of the as-fabricated photodetectors are stable, suggesting the careful thickness selection in next-generation high-performance lead-free all-inorganic perovskites photodetectors.

Synthesis of 2D ternary layered manganese phosphorous trichalcogenides towards ultraviolet photodetection

Manganese phosphorous selenium(MnPSe_(3)),as a representative of layered metal phosphorus trichalcogenides(MPTs),has gained significant attention due to its direct bandgap,high carrier mobility,large absorption coefficient,which indicate great potential in photoelectric application.Herein,high-quality two-dimensional(2D)MnPSe_(3) flakes were mechanically exfoliated from the corresponding bulk crystals synthesized by chemical vapor transport(CVT)methods.The systematic investigation was applied to the lattice vibrations of MnPSe_(3) via angle-resolved polarized Raman spectroscopy(ARPRS),and the Raman vibration modes were determined based on Raman selection rules and crystal symmetry.Impressively,the photodetectors based on 2D MnPSe_(3) flakes exhibit excellent photoresponse to the ultraviolet light with a responsivity up to 22.7 A W^(-1) and a detectivity of 2.4×10^(11) Jones.The high performance in the ultraviolet range signifies that 2D MnPSe_(3) is expected to be a powerful candidate for future ultraviolet photodetection.

Controllable growth of type-II Dirac semimetal PtTe2 atomic layer on Au substrate for sensitive room temperature terahertz photodetection

Platinum telluride(PtTe_(2)),a member of metallic transition metal dichalcogenides,provides a new platform for investigating various properties such as type-II Dirac fermions,topological superconductivity,and wide-band photodetection.However,the study of PtTe_(2)is largely limited to exfoliated flakes,and its direct synthesis remains challenging.Herein,we report the controllable synthesis of highly crystalline 2D PtTe_(2)crystals with tunable morphology and thickness via chemical vapor deposition(CVD)growth on Au substrate.By adjusting Te amount and substrate temperature,anisotropic and isotropic growth modes of PtTe_(2)were realized on the solid and molten Au substrates,respectively.The domain size of PtTe_(2)crystal was achieved up to 30μm,and its thickness can be tuned from 5.6 to 50 nm via controlling the growth time.Furthermore,a metal–PtTe_(2)–metal structural device was fabricated to validate the wide-band terahertz(THz)photodetection from 0.04 to 0.3 THz at room temperature.Owing to the high crystallinity of PtTe_(2)crystal,the photodetector acquires high responsivity(30–250 mA W-1 from 0.12 to 0.3 THz),fast response rate(rise time:7μs,decay time:8μs),and high-quality imaging ability.Our work demonstrates the feasibility for realistic exploitation of high-performing photodetection system at THz band based on the CVDgrown 2D Dirac semimetal materials.