CdSe Nanobelts Research Articles

Artificial optoelectronic synapse based on CdSe nanobelt photosensitized MoS2 transistor with long retention time for neuromorphic application

Abstract Optoelectronic synaptic devices have been regarded as the key component in constructing neuromorphic computing systems. However, the optoelectronic synapses based on conventional 2D transistor are still suffering low photosensitivity and volatile retention behavior, which can affect the recognition accuracy and long-term memory. Here, a novel optoelectronic synaptic device based on surface-state-rich CdSe nanobelt photosensitized 2D MoS2 transistor is demonstrated. Benefiting from the excellent light absorption of CdSe and effective charge trapping at the hetero-interface, the device exhibits not only high photosensitivity but also long retention time (>1,500 s). In addition, typical synaptic functions including the excitatory postsynaptic current, paired-pulse facilitation, the transformation from short-term to long-term plasticity, the transformation from short-term to long-term plasticity, spike-amplitude-dependent plasticity, and learning-forgetting-relearning process are successfully simulated and modulated by light stimulation. Most importantly, an artificial neural network is simulated based on the optical potentiation and electrical habituation characteristics of the synaptic devices, with recognition accuracy rates of 89.2, 93.8, and 91.9 % for file type datasets, small digits, and large digits are achieved. This study demonstrates a simple and efficient way to fabricate highly photosensitive optoelectronic synapse for artificial neural networks by combining the merits of specific materials and device architecture.

Strong interlayer coupling in p-Te/n-CdSe van der Waals heterojunction for self-powered photodetectors with fast speed and high responsivity.

Self-driven photodetectors, which can detect optical signals without external voltage bias, are highly attractive in the field of low-power wearable electronics and internet of things. However, currently reported self-driven photodetectors based on van der Waals heterojunctions (vdWHs) are generally limited by low responsivity due to poor light absorption and insufficient photogain. Here, we report p-Te/n-CdSe vdWHs utilizing non-layered CdSe nanobelts as efficient light absorption layer and high mobility Te as ultrafast hole transporting layer. Benefiting from strong interlayer coupling, the Te/CdSe vdWHs exhibit stable and excellent self-powered characteristics, including ultrahigh responsivity of 0.94 A W-1, remarkable detectivity of 8.36 × 1012 Jones at optical power density of 1.18 mW cm-2 under illumination of 405 nm laser, fast response speed of 24 µs, large light on/off ratio exceeding 105, as well as broadband photoresponse (405-1064 nm), which surpass most of the reported vdWHs photodetectors. In addition, the devices display superior photovoltaic characteristics under 532 nm illumination, such as large Voc of 0.55 V, and ultrahigh Isc of 2.73 µA. These results demonstrate the construction of 2D/non-layered semiconductor vdWHs with strong interlayer coupling is a promising strategy for high-performance and low-power consumption devices.

Bending effect on the energy of a particle in a semiconductor nanobelt

Semiconductor nanostructures have exhibited unique optoelectronic characteristics for a variety of applications, including flexible optoelectronic devices and systems. In this work, we analyze the effect of elastic bending on the eigenvalues (energies) of a particle in a semiconductor nanobelt in the framework of the single-band Schrödinger equation. The electronic state of the particle in the semiconductor nanobelt is described by a quantum well. Using the Airy functions, both the wave function and characteristic equation of the particle are obtained. Numerical results for an electron in a CdSe nanobelt reveal that the ground-state energy of the electron in the bent nanobelt decreases with the increase of the bending deformation and the change of the ground-state energy of the electron in the bent nanobelt decreases with the decrease of the nanobelt thickness.

Constructing high-quality 1D nano/microwire hybrid structure for high-performance photodetectors based on CdSe nanobelt/perovskite microwire

Abstract All-inorganic perovskite CsPbBr3 is considered as a promising photoelectric material due to its high environmental stability and excellent photoelectric properties. Constructing low-dimension hybrid structures by combining CsPbBr3 with semiconductor materials have recently attracted particular attention because they may bring new functionalities or generate synergistic effects in optoelectronic devices. Herein, the high-quality 1D CdSe nanobelt (NB)/CsPbBr3 microwire (MW) photodetectors are designed first time, which exhibit excellent performance as integrating I on/I off ratio of 5.02 × 104, responsivity of 1.63 × 103 A/W, external quantum efficiency of 3.8 × 105% and detectivity up to 5.33 × 1012 Jones. These properties are all improved at least one order of magnitude compared to those of single CsPbBr3 photodetectors. Moreover, the response range is broadened from the 300–570 nm (the single CsPbBr3 device) to 300–740 nm (the hybrid photodetector). Then, the first-principles calculations are carried out to reveal the physical mechanism from the atomic scale. The remarkably improved optoelectronic properties are attributed to the high crystalline quality as well as unique band alignment of hybrid structure that facilitate the effective separation and transport of photogenerated carriers. These works indicate that 1D CdSe/CsPbBr3 hybrid devices have promising applications in building high-performance and broader spectral response photodetectors and other optoelectronic devices.

Lead-Free Perovskite Nanoflake/Monoradicular CdSe Nanobelt Hybrid Nanostructures for Ultrasensitive Broadband Photodetectors

Lead halide perovskites have drawn extensive attention on account of their fundamental role in the field of photoelectric detection. Nevertheless, the existence of toxic lead ions and the instability of lead-based perovskites greatly hamper their applications in mass production and commercialization. Herein, a hybrid photodetector based on the lead-free inorganic perovskite nanoflake (Cs3Sb2Br9 NF)/monoradicular CdSe nanobelt (NB) has been successfully prepared. The hybrid nanostructures promote the effective separation of electron–hole pairs, thus dramatically improving the photoelectric performance. Meanwhile, the Cs3Sb2Br9 NF/CdSe NB photodetector possesses a wideband spectral response from 300 to 780 nm and shows a higher responsivity (174 A/W), external quantum efficiency (4.8 × 104 %), and photodetectivity (1.1 × 1014 Jones) under 448 nm illumination. Overall, these superior photoelectric properties confirm that the Cs3Sb2Br9 NF/CdSe NB is a kind of hybrid optoelectronic device with practical application in civilian and military fields.

High-Performance and Broadband Flexible Photodetectors Employing Multicomponent Alloyed 1D CdSxSe1-x Micro-Nanostructures.

Low-cost multicomponent alloyed one-dimensional (1D) semiconductors exhibit broadband absorption from the ultraviolet to the near-infrared regime, which has attracted a great deal of interest in high-performance flexible optoelectronic devices. Here, we report the facile one-step fabrication of high-performance broadband rigid and flexible photodevices based on multicomponent alloyed 1D cadmium-sulfur-selenide (CdSxSe1-x) micro-nanostructures obtained via a vapor transport route. Photoresponse measurements have demonstrated their superior spectral photoresponsivity (5.8 × 104 A/W), several orders of magnitude higher than the pristine CdSe nanobelt photodevice, high specific detectivity (2 × 1015 Jones), photogain (1.2 × 105), external quantum efficiency (EQE, 1.4 × 107%), rapid response speed (13 ms), and excellent long-term environmental stability. The multicomponent alloyed CdSxSe1-x nanobelt photodevice demonstrated about three times higher photocurrent as well as can operate under multiple color illuminations (200-800 nm) and at a high applied bias of 10 V with the photoresponsivity and EQE being boosted to 4.34 × 105 A/W and 8.96 × 107%, respectively. Furthermore, multicomponent alloyed CdSxSe1-x nanobelt flexible photodevices show excellent mechanical and flexural photostabilities with identical photoresponse as rigid nanodevices. The improvement mechanism found in the present research can be exploited to lead to the design of high-performance flexible photodevices comprising other multicomponent nanomaterials.

Remote Dual-Cavity Enhanced Second Harmonic Generation in a Hybrid Plasmonic Waveguide.

On-chip nanoscale optical platforms capable of efficient second harmonic generation (SHG) are highly desired for optical sensing, subwavelength coherent sources, and quantum photonic devices. Here, we develop a remotely excited dual cavity resonance scheme to achieve significantly enhanced SHG in a CdSe nanobelt on Au film hybrid waveguide system. The SHG emission with superior efficiency originates from counter-propagating plasmonic modes interference in a horizontal Fabry-Pérot (FP) cavity enabled by remote excitation of propagating surface plasmons, which is further enhanced through a vertical FP cavity. With this effective cooperation of hybrid plasmon modes and FP cavity modes, 2 orders of magnitude enhancement of the conversion efficiency (3.5 × 10-4 W-1) is achieved compared to the off-resonance case. Our design provides new insight into the development of a multifunctional hybrid plasmonic device toward on-chip nonlinear nanophotonic applications.

Ultrathin indium vanadate/cadmium selenide-amine step-scheme heterojunction with interfacial chemical bonding for promotion of visible-light-driven carbon dioxide reduction

The formation of interfacial chemical bonding in heterostructures plays an important role in the transport of carriers. Herein, we firstly prepared ultrathin InVO4 nanosheet (Ns) with a thickness of 1.5 nm. Diethylenetriamine-modified CdSe (CdSe-DETA) nanobelts are in-situ deposited on the surface of ultrathin InVO4 Ns to build a InVO4/CdSe-DETA step-scheme (S-scheme) heterojunction photocatalysts. The protonated DETA acts as an amine-bridge to promote the formation of a tight chemical bond at the interface of InVO4/CdSe-DETA, thereby promoting the transfer of carriers at the interface. For photocatalytic CO2 reduction, the rationally designed InVO4/CdSe-DETA S-scheme photocatalyst exhibits a remarkable CO generation rate of 27.9 µmol h−1 g−1 at 420 nm, which is 3.35 and 3.39 times higher than that of CdSe-DETA and InVO4 Ns, respectively. The new method by using interfacial chemical bonding to facilitate interfacial charge transportation provide a promising strategy for improve photocatalysis.

ZnO/CdSe-diethylenetriamine nanocomposite as a step-scheme photocatalyst for photocatalytic hydrogen evolution

ZnO/CdSe-diethylenetriamine (ZnO/CdSe-DETA) nanocomposites are synthesized by a two-step hydrothermal method. The content of CdSe-DETA in the nanocomposites has a significant effect on the photocatalytic activity of hydrogen evolution. Under the irradiation of a xenon lamp with a UV-cutoff filter (λ ≥ 420 nm), the nanocomposite with a CdSe-DETA content of 43.36% reaches a hydrogen evolution rate of 11.09 mol g−1h−1, which is 4.32 and 123.22 times than that of CdSe-DETA and ZnO, respectively. The better photocatalytic hydrogen evolution activity of the ZnO/CdSe-DETA is due to several factors. DETA can be inserted into the interlayer of Cd-Se and form CdSe-DETA nanobelts with large specific surface area. The ZnO/CdSe-DETA nanocomposite has a wide range of light absorption. The step-scheme heterojunction formed between ZnO and CdSe-DETA can significantly enhance the separation and migration of photoinduced electrons and holes, thus improving the photocatalytic performances of the photocatalysts. The addition of Pt as a cocatalyst is helpful to the separation of electrons, and the absorption of visible light can be enhanced by the surface plasmon resonance effect of Pt. This work may be helpful to construct step-scheme photocatalytic systems with high photocatalytic activity for hydrogen evolution.

Barrier Height Inhomogeneity in Mixed-Dimensional Graphene/Single CdSe Nanobelt Schottky Junctions

Mixed-dimensional graphene/single CdSe nanobelt (NB) Schottky junctions are fabricated, and the influence of Schottky barrier inhomogeneity on the electrical transport mechanism is investigated. The ideality factor increases and the zero-bias Schottky barrier height (SBH) decreases monotonically, as temperature decreases from 300 to 80 K. The temperature-dependent electrical transport characteristics can be explained by the SBH inhomogeneity. We use a spatial potential fluctuation model to analyze the conduction mechanism, where the SBH with a Gaussian distribution is assumed. The standard deviations of SBH distribution are up to 13.06% and 14.09% of the mean value of zero-bias SBH in 80–140 and 140–300 K, respectively, implying strong SBH inhomogeneity in typical graphene/CdSe NB junctions.

Photoconductive properties of Er-CdSe nanobelt detectors

Three kinds of devices based on single Er-doped CdSe nanobelt (Er-CdSe NB), single CdSe NB and four CdSe NBs in parallel were constructed by hard mask assisted with 10-μm tungsten wire in diameter. The photoelectronic properties of three kinds of devices were investigated. It is found that the dark currents of Er-CdSe NB and CdSe NB (four CdSe NBs in parallel) are 4 × 10−10 and 1.0 × 10−13 A (8.92 × 10−11 A). They have high Ion/Ioff ratios with 2.21 × 104 and 8.97 × 105 (4.61 × 104), respectively. The corresponding responsivity, external quantum efficiency and detectivity of Er-CdSe NB and CdSe NB (four CdSe NBs in parallel) are 2.17 × 103, 3.87 × 105 and 2.27 × 1012 A/W; 3.84, 692 and 2.9 × 1011; 1.59 × 102, 2.86 × 104 and 4.96 × 1011 Jones. The responsivity Rλ and external quantum η of four CdSe NBs in parallel are higher by two orders of magnitude than that of single CdSe NB device. The detectivity D* of the former is twofold higher than that of the latter. In the meantime, Rλ, η and D* of Er-CdSe NB are 10-fold higher than those of four CdSe NBs in parallel. The superior performance of the Er-CdS NB device offers an avenue to develop highly sensitive photodetector applications.

Layered Inorganic/Organic Hybrid (CdSe) n·Monoamine Nanobelts: Controllable Solvothermal Synthesis, Multiple Stage Amine De-Intercalation Transformation, and Two-Dimensional Exciton Quantum Confinement Effect.

CdSe nanocrystals, including quantum dots and quantum rods, are a research hotspot in nanomaterials. Recently, it has been found that two-dimensional CdSe semiconductor nanobelts show a unique quantum confinement effect owing to their homogeneous nanoscale thickness. In this study, a series of (CdSe) n·monoamine ( n = 1, 2, and 4, monoamine = butylamine, hexylamine, and octylamine) layered inorganic/organic hybrid nanobelts was synthesized by the solvothermal method. These hybrids have a lamellar structure with a few inorganic [CdSe] layers and monoamine layers alternatively stacked along the c axis of their crystallites, which exhibit the typical preferred orientation for layered crystallites and isomorphous [CdSe] layers according to their X-ray diffraction patterns. The [CdSe] layer is a contracted (110) superlattice cell of wurtzite (WZ)-type CdSe with unit cell parameter relations of a ≈ √3 aWZ and b ≈ cWZ, and a lamellar nanobelt morphology with the [010] growth direction. These ordered hybrids exhibit prominent split exciton absorption peaks and sharp band edge luminescence owing to the homogeneous thickness of the [CdSe] layers within the hybrids, all of which are comparable with reported WZ-type CdSe colloidal nanosheets and exhibit a prominent two-dimensional exciton quantum confinement effect. The solvothermal reaction was systematically investigated. The multiple stage amine de-intercalation topotactic process was revealed for the WZ-type CdSe nanobelts with the (CdSe) n·monoamine ( n = 1, 2, and 4) hybrids as the intermediate phases. The solvothermal synthesis method (70-150 °C) is facile and milder than the traditional hot injection method (>200 °C). Therefore, these hybrids can be considered to be intermediate phases or precursors of WZ-type CdSe nanosheets with a topotactic intralayer [CdSe] structure and also a type of multiple quantum well with extremely thin [CdSe] layers orderly stacked among the monoamine insulating blocking layers.

Porous Single-Crystalline CdSe Nanobelts: Cation-Exchange Synthesis and Highly Selective Photoelectric Sensing toward Cu2.

Porous single-crystalline nanostructures are of tremendous interest for their application in the catalytic, electronic and sensing fields due to their large active surfaces, favorable diffusion, and good electronic transport. Despite the recent advances of various other components, photoelectric chalcogenides remain almost undeveloped. The present study contributes a facile strategy to prepare porous single-crystalline CdSe nanobelts through a cation-exchange reaction, in which ZnSe⋅0.5 N2 H4 hybrid nanobelts are employed as precursors. The detailed characterizations indicate the preservation of the belt-like morphology of the precursors due to the spatial confinement effect, which arises from the coated surfactant layer during the cation-exchange process. Simultaneously, CdSe nanobelts with porous and single-crystalline structures are formed following a complete exchange between Zn2+ and Cd2+ , the release of N2 H4 , and the atomic arrangement. The native photoelectric properties of the as-prepared porous single-crystalline CdSe nanobelts are systematically addressed based on the nanodevices fabricated with a single nanobelt and assembled nanobelt array. The results indicate that they present a rapid, stable, and repeatable photoelectric response. Moreover, as-prepared nanobelts exhibit highly selective photoelectric sensing toward Cu2+ with a low detection limit down to 0.1 ppm. To illuminate this phenomenon, a possible sensing mechanism is also discussed.

Highly polarized single mode nanobelt laser

We demonstrate a highly polarized single mode nanobelt laser with a low threshold. Different from the traditional nanobelt lasers, the laser cavity is formed along the lateral direction of the nanobelt and the wavelength is centered at 712.6 nm with a linewidth of about 0.18 nm. The single mode lasing emission is highly polarized with a polarization ratio of about 0.91. Moreover, the threshold is as low as 18 μJ/cm2 which is about an order of magnitude lower than that of the traditional CdSe nanobelt lasers. These low threshold high polarization single mode nanobelt lasers offer great potential as a low cost and energy efficient choice of technology for applications in visible light communications, displays, optical sensing, and environmental monitoring.

Far-Field Subdiffraction Imaging of Semiconductors Using Nonlinear Transient Absorption Differential Microscopy

Label-free absorption spectroscopies are frontline techniques to reveal the spectral fingerprint, composition and environment of materials and are applicable to a wide range of samples. In an effort to improve the spatial resolution of far-field absorption microscopy, which is limited by the diffraction of light, an imaging technique based on transient absorption saturation has recently been developed. Here we report a far-field transient absorption microscopy that does not require the sample to exhibit saturable absorption to break the diffraction barrier. By alternating the wavefront of the pump beams and exploiting a nonlinearity in the transient absorption intrinsic to semiconductors, we demonstrate imaging, beyond the diffraction limit, in CdSe nanobelts. This differential technique is applied for label-free super-resolution absorption microspectroscopy.

Generation of Rashba spin-orbit coupling in CdSe nanowire by ionic liquid gate.

Spintronic devices rely on the spin degree of freedom (DOF), and spin orbit coupling (SOC) is the key to manipulate spin DOF. Quasi-one-dimensional structures, possessing marked anisotropy gives more choice for the manipulation of the spin DOF since the concrete SOC form varies along with crystallographic directions. The anisotropy of the Dresselhaus SOC in cadmium selenide (CdSe) nanobelt and nanowire was studied by circular photogalvanic effect. It was demonstrated that the Dresselhaus SOC parameter is zero along the [0001] crystallographic direction, which suppresses the spin relaxation and increases the spin diffusion length, and thus is beneficial to the spin manipulation. To achieve a device structure with Rashba SOC presence and Dresselhaus SOC absence for manipulating the spin DOF, an ionic liquid gate was produced on a nanowire grown along the [0001] crystallographic direction, and the Rashba SOC was induced by gating, as expected.

Construction of high-quality CdSe NB/graphene Schottky diodes for optoelectronic applications

High-quality CdSe nanobelts (NBs) and monolayer graphene were synthesized via a chemical vapor deposition (CVD) method. Schottky diodes based on CdSe NBs/graphene have been fabricated and investigated. The as-fabricated Schottky diodes exhibit excellent rectification characteristic with rectification ratio up to 103 within ±2V in the dark and distinctive photoresponse to light switching between on and off. Further analysis reveals that the Schottky diodes were highly sensitive to light illumination with very good stability, reproducibility and fast response speeds of 47/122μs. Our results suggest that CdSe NBs/graphene Schottky diodes have potential future application in integrated nano-optoelectronic systems.

Antimony doped cadmium selenium nanobelts with enhanced electrical and optoelectrical properties

Abstract Intrinsic and Sb-doped CdSe nanobelts (NBs) were synthesized via a thermal evaporation technique. The electrical transport properties of field effect transistors (FETs) fabricated using the NBs were investigated. The results indicate that the Sb-doped NBs behave as n-type semiconductors with improved electrical conductivity (10 −1 to 100 S/cm) compared with the intrinsic CdSe. Photodetectors made of single NB were also fabricated and investigated. The results show that Sb-doped NB photodetectors exhibit much higher responsivity (1.5 × 10 4 A/W) and external quantum efficiency (1.2 × 10 5 ) but lower on/off current ratio (∼253) and longer response time (≤40 ms). Furthermore, both electrical transport and optoelectrical properties of the as-synthesized CdSe NBs can be tuned by changing the doping concentration. The results indicate that the as-synthesized NBs are excellent building blocks for constructing electronic and optoelectronic devices.

Enhanced electrical and optoelectrical properties of cadmium selenide nanobelts by chlorine doping

Single-crystalline chlorine-doped cadmium selenide (CdSe) nanobelts (NBs) with a wurtzite structure were synthesised by using CdSe and InCl3 powder as sources via a co-evaporation approach. The investigation of the performance of the field-effect transistors fabricated from Cl-doped NBs shows n-type conduction behaviour and enhanced conductivity (1–70 S/cm). Furthermore, it is found that the photoconductivity (illuminated by a white light with a power density of 1.3 mW/cm2) increases with the enhancement of the conductivity. Photoconductive analysis reveals that the Cl-doped NBs show excellent photoresponse properties, with responsivity of 8.87 × 105 AW−1 and a corresponding external quantum efficiency of 1.74 × 106 when illuminated under a 650 nm light and biased 1 V. In addition, the electrical properties of the Cl-doped NBs can be influenced by changing the ambiance, which is caused by their surface states.

Synthesis of high-quality Cl-doped CdSe nanobelts and their application in nanodevices

High-quality Chlorine (Cl) doped CdSe nanobelts (NBs) with single-crystal wurtzite structure were synthesized by using CdCl2 as the dopant via a thermal co-evaporation method. The n-type conductivity of CdSe NBs was confirmed by field-effect transistors (FETs) based on single NBs. The electron concentration and mobility of these CdSe NBs are about 6.67×1018cm-3 and 17.4cm2/Vs, respectively. High-performance nano-Schottky diodes on single CdSe NBs with Au Schottky contact electrodes have been fabricated and studied. The CdSe NB/Au Schottky diode show an excellent rectification characteristic with a rectification ratio up to 107 within ±1V and small ideality factor of ∼1.2, which can also function as photodetectors with an ultrafast response speed of 26/50μs, representing the best value obtained for the CdSe based nano-photodectecors. These results reveal that such CdSe NBs and their nanodevices have great potential for nano-electronic and optoelectronic applications.