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Reconfigurable image sensors for the recognition and understanding of real-world objects are now becoming an essential part of machine vision technology. The neural network image sensor — which mimics neurobiological functions of the human retina —has recently been demonstrated to simultaneously sense and process optical images. However, highly tunable responsivity concurrently with non-volatile storage of image data in the neural network would allow a transformative leap in compactness and function of these artificial neural networks (ANNs) that truly function like a human retina. Here, we demonstrate a reconfigurable and non-volatile neuromorphic device based on two-dimensional (2D) semiconducting metal sulfides (MoS2 and WS2) that is concurrently a photovoltaic detector. The device is based on a metal/semiconductor/metal (M/S/M) two-terminal structure with pulse-tunable sulfur vacancies at the M/S junctions. By modulating sulfur vacancy concentrations, the polarities of short-circuit photocurrent —can be changed with multiple stable magnitudes. Device characterizations and modeling reveal that the bias-induced motion of sulfur vacancies leads to highly reconfigurable responsivities by dynamically modulating the Schottky barriers. A convolutional neuromorphic network (CNN) is finally designed for image process and object detection using the same device. The results demonstrated the two-terminal reconfigurable and non-volatile photodetectors can be used for future optoelectronics devices based on coupled Ionic-optical-electronic effects for Neuromorphic computing.

Multi-resonance light coupling management is a promising way to expand the operating spectral ranges of optoelectronic devices. The classical strategies are either lack of independent tunability for each resonance or involved with complex fabrication. Here, we propose a new scheme for expanding the operating spectral range of an optoelectronic device through a dual-color active material integrated with a simple resonant waveguide structure. The TM waveguide mode and the SPP mode of the resonant waveguide structure are regulated to match the two active regions of the dual-color material both spectrally and spatially. Applying this scheme to a long-wavelength infrared quantum well photodetector, the absorption efficiencies at the two peak detection wavelengths of the dual-color quantum wells are both enhanced by more than 10 times compared with the case of a standard 45° edge facet coupled device with the same detection material. The simple light coupling structure is easy to accomplish and compatible with focal plane arrays. For thermal radiation detection, the absorption efficiency of the 300 K blackbody radiation by our dual-color detector is 83.8% higher than that by a single-color detector with the optimized structural parameters. Moreover, either polarization sensitive or polarization insensitive detection could be achieved in this dual-color infrared quantum well photodetector by using anisotropic or isotropic gratings.

Two-dimensional (2D) infrared photodetectors always suffer from low quantum efficiency (QE) because of the limited atomically thin absorption. Here, we reported 2D black phosphorus (BP)/Bi 2 O 2 Se van der Waals (vdW) photodetectors with momentum-matching and band-alignment heterostructures to achieve high QE. The QE was largely improved by optimizing the generation, suppressing the recombination, and improving the collection of photocarriers. Note that momentum-matching BP/Bi 2 O 2 Se heterostructures in k -space lead to the highly efficient generation and transition of photocarriers. The recombination process can be largely suppressed by lattice mismatching–immune vdW interfaces. Furthermore, type II BP/Bi 2 O 2 Se vdW heterostructures could also assist fast transport and collection of photocarriers. By constructing momentum-matching and band-alignment heterostructures, a record-high QE of 84% at 1.3 micrometers and 76.5% at 2 micrometers have been achieved in BP/Bi 2 O 2 Se vdW photodetectors.

Homojunctions and homosuperlattices are essential structures and have been widely explored for use in advanced electronic and optoelectronic devices. However, artificially manipulating crystalline phases in two-dimensional (2D) monolayers is still challenging, especially when attempting to engineer lateral homogeneous junctions in a single monolayer of transition metal dichalcogenides (TMDs). Herein, we demonstrate a lateral homosuperlattice (MLHS) with alternating 1T and 2H domains in a 2D WS

Hot carrier harvest could save 30% energy loss in solar cells. So far, however, it is still unreachable as the photoexcited hot carriers are short-lived, ∼1 ps, determined by a rapid relaxation process, thus invalidating any reprocessing efforts. Here, we propose and demonstrate a feasible route to reserve hot electrons for efficient collection. It is accomplished by an intentional mix of cubic zinc-blend and hexagonal wurtzite phases in III-V semiconductor nanowires. Additional energy levels are then generated above the conduction band minimum, capturing and storing hot electrons before they cool down to the band edges. We also show the superiority of core/shell nanowire (radial heterostructure) in extracting hot electrons. The strategy disclosed here may offer a unique opportunity to modulate hot carriers for efficient solar energy harvest.

2D materials, of which the carrier type and concentration are easily tuned, show tremendous superiority in electronic and optoelectronic applications. However, the achievements are still quite far away from practical applications. Much more effort should be made to further improve their performance. Here, p-type MoSe

Generally, for gas imaging, narrowing the response of the camera sensor around the target gas’s absorption band would increase the imaging contrast. In this paper, A filter-free narrowband metallic cavity quantum well infrared photodetector is proposed. The metallic cavity is formed by Ti/Au film coating on the detector’s mesa. The geometry of the cavity is properly designed to sustain cavity mode resonating at 10.6 μm. With strong resonance, the absorption efficiency of the embedded quantum well active layer maintains high level (~ 74%) even with a fairly low doping concentration (~ 1 × 1017 cm−3). And the bandwidth is as narrow as 0.22 μm. A waveguide model is presented and used to analyze the metal cavity quantum well infrared photodetector, and it is found that the metal film coating on the side wall played an important role in enhancing the resonance and narrowing the spectral line width.

One-dimensional InAs nanowire (NW)-based photodetectors have been widely studied due to their potential application in mid-wavelength infrared (MWIR) photon detection. However, the limited performance and complicated photoresponse mechanism of InAs NW-based photodetectors have held back their true potential for real application. In this study, we developed ferroelectric polymer P(VDF-TrFE)-coated InAs NW-based photodetectors and demonstrated that the electrostatic field caused by polarized ferroelectric materials modifies the surface electron–hole distribution as well as the band structure of InAs NWs, resulting in ultrasensitive photoresponse and a wide photodetection spectral range. Our single InAs NW photodetectors exhibit a high responsivity (R) of 1.6 × 104 A W–1 as well as a corresponding detectivity (D*) of 1.4 × 1012 cm·Hz1/2 W–1 at a light wavelength of 3.5 μm without an applied gate voltage, ∼3–4 orders higher than the maximum value of photoresponsivity reported or commercially used MWIR photode...

Low-dimensional Te-based photodetectors exhibit blackbody response and achieve record-set performance metrics., Blackbody-sensitive room-temperature infrared detection is a notable development direction for future low-dimensional infrared photodetectors. However, because of the limitations of responsivity and spectral response range for low-dimensional narrow bandgap semiconductors, few low-dimensional infrared photodetectors exhibit blackbody sensitivity. Here, highly crystalline tellurium (Te) nanowires and two-dimensional nanosheets were synthesized by using chemical vapor deposition. The low-dimensional Te shows high hole mobility and broadband detection. The blackbody-sensitive infrared detection of Te devices was demonstrated. A high responsivity of 6650 A W−1 (at 1550-nm laser) and the blackbody responsivity of 5.19 A W−1 were achieved. High-resolution imaging based on Te photodetectors was successfully obtained. All the results suggest that the chemical vapor deposition–grown low-dimensional Te is one of the competitive candidates for sensitive focal-plane-array infrared photodetectors at room temperature.

2D materials, of which the carrier type and concentration are easily tuned, show tremendous superiority in electronic and optoelectronic applications. However, the achievements are still quite far away from practical applications. Much more effort should be made to further improve their performance. Here, p-type MoSe2 is successfully achieved via substitutional doping of Ta atoms, which is confirmed experimentally and theoretically, and outstanding homojunction photodetectors and inverters are fabricated. MoSe2 p-n homojunction device with a low reverse current (300 pA) exhibits a high rectification ratio (104 ). The analysis of dark current reveals the domination of the Shockley-Read-Hall (SRH) and band-to-band tunneling (BTB) current. The homojunction photodetector exhibits a large open-circuit voltage (0.68 V) and short-circuit currents (1 µA), which is suitable for micro-solar cells. Furthermore, it possesses outstanding responsivity (0.28 A W-1 ), large external quantum efficiency (42%), and a high signal-to-noise ratio (≈107 ). Benefiting from the continuous energy band of homojunction, the response speed reaches up to 20 µs. Besides, the Ta-doped MoSe2 inverter exhibits a high voltage gain (34) and low power consumption (127 nW). This work lays a foundation for the practical application of 2D material devices.

For each generation of semiconductors, the issue of doping techniques is always placed at the top of the priority list since it determines whether a material can be used in the electronic and optoelectronic industry or not. When it comes to 2D materials, significant challenges have been found in controllably doping 2D semiconductors into p- or n-type, let alone developing a continuous control of this process. Here, a unique self-modulated doping characteristic in 2D layered materials such as PtSSe, PtS0.8 Se1.2 , PdSe2 , and WSe2 is reported. The varying number of vertically stacked-monolayers is the critical factor for controllably tuning the same material from p-type to intrinsic, and to n-type doping. Importantly, it is found that the thickness-induced lattice deformation makes defects in PtSSe transit from Pt vacancies to anion vacancies based on dynamic and thermodynamic analyses, which leads to p- and n-type conductance, respectively. By thickness-modulated doping, WSe2 diode exhibits a high rectification ratio of 4400 and a large open-circuit voltage of 0.38 V. Meanwhile, the PtSSe detector overcomes the shortcoming of large dark-current in narrow-bandgap optoelectronic devices. All these findings provide a brand-new perspective for fundamental scientific studies and applications.

In order to meet the needs of the development of long wave HgCdTe infrared focal plane devices, this paper summarizes the related research progress from two aspects: the p-type doping mechanism of materials and the low-frequency noise of devices. It includes: (1) the classical p-type activation model of as doping is modified theoretically, and a new activation model is proposed, that is, as migration dominated by composite defect TeHg-VHg leads to the formation of AsTe2 complex, which shows p-type. (2) It is theoretically explained that the fast diffusion characteristics of Au doped HgCdTe are caused by the interstitial diffusion mechanism; a method is proposed to control the spatial distribution of Au impurities through the interaction between Au impurities and Hg vacancies, which can realize controllable p-type doping and is verified by experiments. (3) A high sensitivity and low frequency noise test system is built. Combined with the numerical calculation model, the evaluation method of low-frequency noise is established. At the same time, the origin of low-frequency noise of long wave HgCdTe device is analyzed.

The long wavelength infrared polarimetric detector can greatly improve the recognition ability of thermal imaging. Owing to the physical limitation of the diffraction limit, the polarization extinction ratio of the current micro-grid polarizer-type long wavelength infrared polarimetric detectors can basically only be as high as about 10∶1. In this paper, a metal/dielectric/metal plasmonic microcavity structure has been fabricated, with the infrared detection active layer of the quantum wells being embedded inside the microcavity. Due to the near-field coupling between the upper grating and bottom reflector metals, a lateral Fabry-Perot resonance was established in the double-metal region, forming the plasmonic microcavity. Benefited from the mode selection characteristics of the microcavity and its resonant coupling with the quantum well intersubband transition, the normal incident light, which cannot be directly absorbed by the intersubband transition of the quantum wells, was coupled into the plasmonic microcavity, transforming its propagation direction into lateral and being absorbed by the quantum wells. The mechanism was confirmed by finite element simulation and the microcavity key parameters such as the grating width and the thicknesses were designed and optimized. Such a structure was applied to the detecting pixels sized at 27 × 27 μm, which was suitable for focal plane arrays. Resulting from the capture and confinement of the incident photons, the detectivity of the detecting pixels could be promoted by about one order of magnitude comparing to the un-structured 45o edge facet coupled detector fabricated from the same epitaxy wafer. The polarization extinction ratio greater than 100∶1 at about 13.5 μm of detecting peak wavelength in the long wavelength infrared waveband was achieved, while the peak intensity dependence on the polarizer azimuth angle fitted Malus law very well. Such a work provides a novel physical foundation and technical route for the development of high extinction ratio long wavelength infrared polarimetric imaging focal planes.

We present a joint experimental and theoretical investigation on a long wavelength infrared quantum cascade detector to reveal its dark current paths. The temperature dependence of the dark current is measured. It is shown that there are two different transport mechanisms, namely resonant tunneling at low temperatures and thermal excitation at higher temperature, dominate the carrier flow, respectively. Moreover, the experimental intersubband transition energies obtained by the magneto-transport measurements matches the theoretical predictions well. With the aid of the calculated band structures, we can explain the observed oscillation phenomena of the dark current under the magnetic field very well. The obtained results provide insight into the transport properties of quantum cascade detectors thus providing a useful tool for device optimization.

Atomically thin 2D-layered transition-metal dichalcogenides have been studied extensively in recent years because of their intriguing physical properties and promising applications in nanoelectronic devices. Among them, ReSe2 is an emerging material that exhibits a stable distorted 1T phase and strong in-plane anisotropy due to its reduced crystal symmetry. Here, the anisotropic nature of ReSe2 is revealed by Raman spectroscopy under linearly polarized excitations in which different vibration modes exhibit pronounced periodic variations in intensity. Utilizing high-quality ReSe2 nanosheets, top-gate ReSe2 field-effect transistors were built that show an excellent on/off current ratio exceeding 10(7) and a well-developed current saturation in the current-voltage characteristics at room temperature. Importantly, the successful synthesis of ReSe2 directly onto hexagonal boron nitride substrates has effectively improved the electron motility over 500 times and the hole mobility over 100 times at low temperatures. Strikingly, corroborating with our density-functional calculations, the ReSe2-based photodetectors exhibit a polarization-sensitive photoresponsivity due to the intrinsic linear dichroism originated from high in-plane optical anisotropy. With a back-gate voltage, the linear dichroism photodetection can be unambiguously tuned both in the electron and hole regime. The appealing physical properties demonstrated in this study clearly identify ReSe2 as a highly anisotropic 2D material for exotic electronic and optoelectronic applications.

The effect of lithium adsorption on the phase transition from 1H-MoS2 to 1T-MoS2 is studied by first-principles computations. The results indicate the possibilities of the phase transition for the lithium adsorption. Based on the results of charge density difference and charge-transfer of molybdenum disulfide with lithium adsorption, we elucidated that the mechanism of the changes of electronic property accompanying the phase transition is attributed to the electron transfer of different atoms. According to the result of transition state, it can be found that the phase-transition barrier is related to the coverage of lithium atoms on MoS2 surface. It may be helpful to obtaining experimentally the stable 1T-MoS2 structure.

We demonstrate the type-II staggered band alignment in MoTe2/MoS2 van der Waals (vdW) heterostructures and an interlayer optical transition at ∼1.55 μm. The photoinduced charge separation between the MoTe2/MoS2 vdW heterostructure is verified by Kelvin probe force microscopy (KPFM) under illumination, density function theory (DFT) simulations and photoluminescence (PL) spectroscopy. Photoelectrical measurements of MoTe2/MoS2 vdW heterostructures show a distinct photocurrent response in the infrared regime (1550 nm). The creation of type-II vdW heterostructures with strong interlayer coupling could improve our fundamental understanding of the essential physics behind vdW heterostructures and help the design of next-generation infrared optoelectronics.

We have studied the polytypism induced by the chemical potential through an ab-initio-thermodynamic-combined approach in Au-catalyzed GaAs nanowire growth. The nucleation in nanowire growth is numerically discussed by classical nucleation theory parameterized by ab initio calculations on the formation energies of the GaAs surfaces and steps. By using the approach we found that the polytypism induced by chemical potential could be explained by the energy competition of lateral walls of the nucleus very well. Furthermore, the obtained results confirmed that the driving force of wurtzite phase nucleation originates from the lower formation energy of its (1 0 ⿿1 0) surface.

Low-symmetry 2D materials with unique anisotropic optical and optoelectronic characteristics have attracted a lot of interest in fundamental research and manufacturing of novel optoelectronic devices. Exploring new and low-symmetry narrow-bandgap 2D materials will be rewarding for the development of nanoelectronics and nano-optoelectronics. Herein, sulfide niobium (NbS3 ), a novel transition metal trichalcogenide semiconductor with low-symmetry structure, is introduced into a narrowband 2D material with strong anisotropic physical properties both experimentally and theoretically. The indirect bandgap of NbS3 with highly anisotropic band structures slowly decreases from 0.42 eV (monolayer) to 0.26 eV (bulk). Moreover, NbS3 Schottky photodetectors have excellent photoelectric performance, which enables fast photoresponse (11.6 µs), low specific noise current (4.6 × 10-25 A2 Hz-1 ), photoelectrical dichroic ratio (1.84) and high-quality reflective polarization imaging (637 nm and 830 nm). A room-temperature specific detectivity exceeding 107 Jones can be obtained at the wavelength of 3 µm. These excellent unique characteristics will make low-symmetry narrow-bandgap 2D materials become highly competitive candidates for future anisotropic optical investigations and mid-infrared optoelectronic applications.

A quantum well-integrated metallic microcavity infrared photodetector is designed and fabricated to achieve highly polarized narrowband wavelength selective detection. Linear grooves are etched on top of the mesa and then the whole device is completely coated with Ti/Au to form an open metallic microcavity, and the resonant mode of the metallic cavity can be detected by the embedded quantum well active layer. The obtained devices show very narrow wavelength selective detection ability as well as strong polarization-dependent characteristics. High performances such as a quality factor of 60 and a polarization extinction ratio of 146 are noticed. Our work provides a promising basis for developing highly integrated infrared cameras with a remarkable performance.

We report on the effects of two different molecular beam epitaxy growth modes on the performance of In0.14Ga0.86As/GaAs quantum well infrared photodetectors (QWIPs). The performance of quantum well (QW) materials are characterized by photoluminescence (PL), x-ray diffraction, and high resolution transmission electron microscope, and a systematic photoelectric characterization is carried out for these InGaAs/GaAs QWIPs. The results indicate that the introduction of continuous low temperature growth can effectively reduce In atom interdiffusion while maintaining the higher PL intensity. QWIPs grown by the low temperature method show the bound-to-bound intraband transition mode as initially designed, whereas the high temperature during the growth makes the operating mode of the device changing to bound-to-quasi continuous mode, which affects the performance of the quantum well infrared photodetectors. Compared with InGaAs/GaAs QWIP fabricated by the temperature-changed growth method, the peak responsivity of the low-temperature grown sample is increased by a factor of 38 and reaches 5.67 A W−1 at 20 K, indicating high responsivity of InGaAs/GaAs QWIP. The reason is attributed to the pronounced increase of photoconductive gain in the device with the B–B working mode. Furthermore, the background limited performance temperature (T BLIP) of low-temperature grown QWIPs is improved by ~10 K.

Interlayer electronic and mechanical couplings of transitional metal dichalcogenides (TMDs) due to Van der Waals force determine their band structure and Raman modes evolution, respectively. We have synthesized twist-stacked WS2 bilayers with twist angles of 0°, 13°, 30°, 41°, 60°, and 83° via chemical-vapor deposited, which allows us to study the coupling effect by Raman and photoluminescence spectroscopy and density function calculation. The photoluminescence property implies that these random-twisted WS2 bilayers behave as quasidirect bandgap material due to weakened interlayer coupling as a result of larger interlayer distances than the non-twisted 0° and 60° stacked WS2 bilayers (with an indirect band gap). In addition, an additional small peak (AI) near the excitonic transition peak (A) is observed from the twisted bilayers, which can be attributed to the interlayer exciton transition. MOE (Min. of Education, S’pore) Accepted version

A method of controlling the morphology of SnTe nanostructures produced by a simple chemical vapor deposition is presented, in which Au-containing catalysts with different Au concentrations are used to induce specific growth behavior. Triangular SnTe nanoplates with a {100} dominated surface and {100}, {111} and {120} side facets were induced by AuSn catalysts, whereas SnTe nanowires with four nonpolar {100} side-facets were produced using Au5Sn catalysts. Through detailed structural and chemical characterization, coupled with surface energy calculations, it is found that nanowire growth is thermodynamically controlled via a vapor-solid-solid growth mechanism, whereas nanoplate growth is kinetically controlled via a vapor-liquid-solid growth mechanism. Therefore, this study provides a fundamental understanding of the catalyst’s role in the growth of IV-VI compound nanostructures.

Strain engineering is an effective method to tune the properties of electrons and phonons in semiconductor materials, including two-dimensional (2D) layered materials (e.g., MoS2 or graphene). External artificial stress (ExAS) or heterostructure stacking is generally required to induce strains for modulating semiconductor bandgaps and optoelectronic functions. For layered materials, the van der Waals-stacked interlayer interaction (vdW-SI) has been considered to dominate the interlayer stacking and intralayer bonding. Here, we demonstrate self-induced uniaxial strain in the MoS2 monolayer without the assistance of ExAS or heterostructure stacking processes. The uniaxial strain occurring in local monolayer regions is manifested by the Raman split of the in-plane vibration modes E2g(1) and is essentially caused by local vdW-SI within the single layer MoS2 due to a unique symmetric bilayer stacking. The local stacked configuration and the self-induced uniaxial strain may provide improved understanding of the fundamental interlayer interactions and alternative routes for strain engineering of layered structures.

Although molecular beam epitaxy technology-based arsenic-doped Hg1−x Cd x Te has been extensively studied, according to the newly proposed framework of the defect-complex-based p-type doping mechanism, heavier group V elements such as antimony (Sb) should have a different doping behavior because of their larger radius which can cause larger lattice distortion. In this work, we performed first-principles calculations and took As and Sb as examples to study this issue. The substitutional doping, interstitial doping (including split, tetrahedral, and hexagonal interstitial sites), and defect complex doping forms for arsenic and antimony are all investigated. A significant lattice distortion is found in hexagonal and split-site interstitial-Sb-doped Hg0.75Cd0.25Te due to the larger covalent radius of Sb. Compared with As, Sb can lead to a more complicated configuration change in the case of SbHg-V Hg-SbHg tridoping, and the interstitial Sb is found to be stable even with the coupling of Hg vacancies through detailed energetic calculations, indicating that the interstitial Sb has greater ability to form stable defect complexes, and thus great potential to be a more appropriate p-type dopant. This study provides more complementary understanding of the behaviors of group V impurities in HgCdTe.

Quantum dots/graphene (QDs/Gr) composites have become the research hotspot recently due to their unique synergistic effect as optical absorption material for next-generation electronic and optoelectronic devices. In this work, Ge QDs/Gr composite is prepared by a simple and effective ion-beam sputtering deposition technique. The intact growth evolution process is detailly investigated by means of the effect of Ge deposition amount, which will induce the enhanced crystallinity in QDs and the reduced defects in graphene. Moreover, a feasible and inspiring strategy to effectively tune doping in graphene by artificial control through changing the deposition amount of Ge atoms on graphene is demonstrated. In addition, charge transfer and interaction strength at the interface of Ge QD and graphene is influenced via the oxygen defect in the QD surface, which is consistent with field-effect transistor test and first-principle calculations. The p-doping characteristics of graphene decorated by Ge QDs may have significant application prospects in energy band engineering of graphene-based building blocks for graphene-based composite development and near-infrared detector applications.

The cut-off wavelength is one of the most important indicators for infrared detectors, and the manipulation of the cut-off wavelength is always an important demand in the application of long wavelength infrared detection. Traditional approaches to the cut-off wavelength extension would inevitably change the electronic states of the devices and lead to a large increase in the dark current, which usually causes performance degradations. Here, we demonstrate an optical method of the cut-off wavelength manipulation by plasmonic microcavities with the dark current being unchanged. We fabricate pixel-level devices with a single quantum well sandwiched in the microcavity and manipulate the cut-off wavelength from 14.3 to 16.3 μm while maintaining the peak responsivity higher than that of the standard 45° polished facet device. The experimental results are in good agreement with the numerical simulations, which indicates that the mechanism is mainly due to the properties of the dual mode manipulation in the plasmonic microcavities.

The configurations of nuclei in Au catalyzed Si nanowire growth were investigated through an ab-initio thermodynamic-combined approach. We discussed the relation between the configurations and formation energies of the lateral walls of the nucleus in nanowire growth numerically by the classical nucleation theory. The nucleation model was parameterized by the formation energies of surfaces, interfaces and steps calculated in first-principles methods. The configurations of the nuclei were determined by the Wulff theorem. Moreover, we found configurations of the nuclei are different in two different Si-Au contact structures. This study provides an important basis to understand the step-flow process in nanowire growth.

We demonstrate the type-II staggered band alignment in MoTe2/MoS2 van der Waals (vdW) heterostructures and an interlayer optical transition at ∼1.55 μm. The photoinduced charge separation between the MoTe2/MoS2 vdW heterostructure is verified by Kelvin probe force microscopy (KPFM) under illumination, density function theory (DFT) simulations and photoluminescence (PL) spectroscopy. Photoelectrical measurements of MoTe2/MoS2 vdW heterostructures show a distinct photocurrent response in the infrared regime (1550 nm). The creation of type-II vdW heterostructures with strong interlayer coupling could improve our fundamental understanding of the essential physics behind vdW heterostructures and help the design of next-generation infrared optoelectronics.

We report the modulation of emission energy, exciton dynamics and lasing properties in a single buckled CdS nanoribbon (NR) by strain-engineering. Inspired by ordered structure fabrication on elastomeric polymer, we develop a new method to fabricate uniform buckled NRs supported on polydimethylsiloxane (PDMS). Wavy structure, of which compressive and tensile strain periodically varied along the CdS NR, leads to a position-dependent emission energy shift as large as 14 nm in photoluminescence (PL) mapping. Both micro-PL and micro-reflectance reveal the spectral characteristics of broad emission of buckled NR, which can be understood by the discrepancy of strain-induced energy shift of A- and B-exciton of CdS. Furthermore, the dynamics of excitons under tensile strain are also investigated; we find that the B-exciton have much shorter lifetime than that of redshifted A-exciton. In addition, we also present the lasing of buckled CdS NRs, in which the strain-dominated mode selection in multi-mode laser and negligible mode shifts in single-mode laser are clearly observed. Our results show that the strained NRs may serve as new functional optical elements for flexible light emitter or on-chip all-optical devices.

Cellphone recycling website with advantages such as convenience, efficiency, professionalism and environmental protection, and many other advantages, has become into a new channel for recycling of waste cellphones. And the key for its popularity and successful operation is to obtain the initial trust of consumers. For the influencing factors of initial trust of websites, scholars have researched a lot from the aspects of site factors, consumer and environmental factors. On the basis of previous studies, this paper combines with the characteristics of cellphone recycling sites, considers the effects the environmental responsibility performance of recycling sites and consumer awareness of environmental protection have on initial trust.

We report the investigation of exciton dynamics in type-II self-assembled GaSb/GaAs quantum dots. The GaSb/GaAs quantum dots (QDs) were grown using a modified liquid phase epitaxy technique. Statistical size distributions of the uncapped QDs were investigated experimentally by field-emission scanning electron microscopy (SEM) and atomic force microscopy (AFM), and theoretically by an eight-band k · p calculation, which demonstrated a dissolution effect. Furthermore, the low-temperature luminescence spectra of type-II GaSb/GaAs QDs with a thick capping layer exhibit well-resolved emission bands and LO-phonon-assisted transitions in the GaSb wetting layer. However, the luminescence lines quench at temperatures above 250 K, which is attributed to the weak quantum confinement of electrons participating in indirect exciton recombination. It was demonstrated that the room temperature stability of the excitons in type-II GaSb/GaAs QDs could be achieved by growing thin a capping layer, which provides strong quantum confinement in the conduction band and enhances the electron-hole Coulomb interaction, stabilizing the excitons.

The surface and size effects on the structural stability and electronic properties of InAs one-dimensional nanostructures are investigated by first-principles calculations within density functional theory. No matter what the diameters, the nanowires are more energetically favorable than the nanotubes due to the preferable sp3 hybridization for In and As atoms in the InAs nanostructures. The formation energies of these nanostructures satisfy a linear dependence relationship with the surface atom ratio. The calculated band structures reveal that the band gaps of InAs nanostructures are determined by two competition mechanisms. One is the quantum confinement effect, which favors the increase of the band gaps with the decreasing diameter or wall thickness. Another is the effect of surface dangling bonds, which induces the decrease of the band gaps with the decreasing diameter or wall thickness. With the same diameter, the band gaps of InAs nanowires are still less than those of the nanotubes. The result indic...

A novel structure to achieve long wavelength infrared broadband detection ranging from 7.6–10.4 µm is proposed via quantum cascade detector. With a pair of identical coupled quantum wells separated by a thin barrier, acting as absorption regions, the relative linewidth (ΔE/E) of response can be dramatically broadened to 30.7%. Moreover, this structure introduces about 30% enhancement in blackbody responsivity. It is shown that the spectral shape can be tuned by the bias voltage effectively, while it is insensitive to the working temperature. The device can work at liquid nitrogen temperature with Johnson noise limited blackbody detectivity of 5.4 × 108 Jones.