CdS Nanobelts Research Articles

Toward low-power-consumption source-gated phototransistor

The power consumption is challenging the next-generation electronic and optoelectronic devices. In this Letter, the n-type source-gated transistor (SGT) enabled by CdS nanobelt is investigated in detail, demonstrating the expected low power consumption, along with impressive photodetection performance. The SGT is realized by deliberately introducing the Schottky barrier at the source of the staggered-electrode transistor, exhibiting a small saturated voltage (VSAT) of 0.84 ± 0.21 V and a remarkably low power consumption of 7.56 ± 4.01 nW. Under illumination, the as-constructed SGT also shows a low power consumption of 7.58 nW, which is much lower than that of the most reported phototransistors operating in the saturated region. Moreover, the source-gated phototransistor also shows a high responsivity of 2.54 × 103 A W−1 and a high detectivity of 6.72 × 1012 Jones. All results imply that the as-constructed low-power-consumption source-gated phototransistor promises next-generation high-performance electronic and optoelectronic devices.

Epitaxial Growth of CsPbBr3 Pyramids/CdS Nanobelt Heterostructures for High-Performance Photodetectors.

Perovskites have great potential for optoelectronic applications due to their high photoluminescence quantum yield, large absorption coefficient, great defect tolerance, and adjustable band gap. Perovskite heterostructures may further enhance the performance of optoelectronic devices. So far, however, most of perovskite heterostructures are fabricated by mechanical stacking or spin coating, which could introduce a large number of defects or impurities at the heterointerface owing to the random stacking process. Herein, we report the epitaxial growth of CsPbBr3 pyramids/CdS nanobelt heterostructures via a 2-step vapor deposition route. The CsPbBr3 triangular pyramids are well aligned on the surface of CdS nanobelts with the epitaxial relationships of (0-22)CsPbBr3||(1-20)CdS and (-211)CsPbBr3||(002)CdS. Time-resolved photoluminescence results reveal that effective charge transfer occurred at the heterointerface, which can be attributed to the type-II band arrangement. Theoretical simulations reveal that the unique CsPbBr3 pyramids/CdS nanobelt structure facilitates diminishing the reflection losses and enhancing the light absorption. The photodetector based on these CsPbBr3 pyramids/CdS nanobelt heterostructures exhibited an ultrahigh photoswitching ratio of 2.14 × 105, a high responsivity up to 4.07 × 104 A/W, a high detectivity reaching 1.36 × 1013 Jones, fast photoresponses (τrise = 472 μs and τdecay = 894 μs), low dark current, and suppressed hysteresis.

A CsPbBr3/CdS-based hybrid bidirectional optoelectronic device with light-emitting, modulation, and detection functions

Optoelectronic integrated circuits, with a broad photonic transportation bandwidth, have emerged as a promising solution to fulfill the escalating demands for high-volume information transportation and processing. However, challenges persist in developing optoelectronic integrated circuits based on low-dimensional nanostructures, including limited integration density and high energy consumption. Here, we demonstrate a bidirectional optoelectronic device by integrating a light-emitting/harvesting CsPbBr3 nanoplate with a waveguiding/modulating/detecting CdS nanobelt. By configuring the CsPbBr3 nanoplate in a Schottky-type device structure with a metal electrode, bright electroluminescence was attained at a bias voltage of 18 V. Thanks to the electric field-tuned phonon-coupling effect, the waveguided light in the CdS nanobelt exhibited a high modulation depth of up to 94%, rendering it an excellent building block as optical modulators and optical switches. Moreover, the integrated nanostructure device showcased functionality in the photodetection mode. The proposed device architecture holds promise for broader applications, potentially extending to other perovskite-coupled II–VI semiconductor optoelectronic integrated circuits for expanding integration capacity and enhancing optoelectronic performance.

Hybrid Polyrhizal CdS Nanobelts/All‐Inorganic Perovskite Nanoflake Heterojunction toward Ultrahigh‐Performance Optoelectronic Devices

AbstractBoth all‐inorganic lead‐free perovskite and CdS nanobelts possess outstanding photo‐detective properties. Herein, a hybrid photodetector based on four CdS nanobelts (NBs)/Cs3Sb2Br9 nanoflake (NF) heterojunction fabricated by a dry‐transfer tactic is designed. In this structure, four parallel CdS nanobelts almost fully cover the Cs3Sb2Br9 NF so that their photoelectronic advantage is demonstrated. The Cs3Sb2Br9 is exploited as an efficient light absorber and component for the construction of type‐II energy band with CdS. Compared with a single CdS NB/Cs3Sb2Br9 NF device, the hybrid four CdS NBs/Cs3Sb2Br9 NF device increases the hybrid area ratio of the channel from 36% to 86%, and demonstrates an appealing performance on an ultrahigh ON/OFF current ratio of 1.54 × 105, remarkable responsivity of 4.13 × 103 A W−1, large detectivity of 1.47 × 1015 Jones, and tremendous external quantum efficiency of 1.14 × 106 %, which are 9.5, 3.8, 7.2, and 3.8 times greater than the single CdS NB/Cs3Sb2Br9 NF device, respectively. Moreover, the photoresponse wavelength of the hybrid four CdS NBs/Cs3Sb2Br9 NF device is broadened to 400–520 nm. This work offers a strategy to enhance the photoelectric performance of hybrid devices, along with the illustration of vital insight into advanced device designs for violet‐green photodetectors.

Effect of Al doping on photoluminescence and conductivity of 1D CdS nanobelts synthesized by CVD for optoelectronic applications

One-dimensional Al-doped CdS nanobelts were synthesized for the first time via chemical vapor deposition. The vertically synthesized Cd 1- x Al x S nanobelts ( x = 0–3.09) exhibited high crystallinity. We have reported here an investigation of optical and electrical properties of prepared nanobelts for potential applications in nano-optoelectronics. The successful incorporation of Al into individual CdS nanobelts was confirmed by powder X-ray diffraction analysis, energy-dispersive X-ray spectroscopy, and Raman spectroscopy. Photoluminescence spectra showed multiple peaks; one emission band appeared at 728 nm (red emission), and a new broad emission band consisting of three peaks centered at 930–961 nm (NIR-1), 954–992 nm (NIR-2), and 1042 nm (NIR-3) appeared in the near-infrared (NIR). All the NIR peaks correspond to the d–d transition of Al ions. Doping with 3.09% Al increased the conductivity of the samples from 1.097 × 10 −6 to 2.59 × 10 −5 A, indicating suitability for optoelectronic applications, including nanoscale light sources and buffer layer materials in solar panels.

Mixed-dimensional Te/CdS van der Waals heterojunction for self-powered broadband photodetector

The 2D layered crystals can physically integrate with other non-2D components through van der Waals (vdW) interaction, forming mixed-dimensional heterostructures. As a new elemental 2D material, tellurium (Te) has attracted intense recent interest for high room-temperature mobility, excellent air-stability, and the easiness of scalable synthesis. To date, the Te is still in its research infancy, and optoelectronics with low-power consumption are less reported. Motivated by this, we report the fabrication of a mixed-dimensional vdW photodiode using 2D Te and 1D CdS nanobelt in this study. The heterojunction exhibits excellent self-powered photosensing performance and a broad response spectrum up to short-wave infrared. Under 520 nm wavelength, a high responsivity of 98 mA W−1 is obtained at zero bias with an external quantum efficiency of 23%. Accordingly, the photo-to-dark current ratio and specific detectivity reach 9.2 × 103 and 1.9 × 1011 Jones due to the suppressed dark current. This study demonstrates the promising applications of Te/CdS vdW heterostructure in high-performance photodetectors. Besides, such a mixed-dimensional integration strategy paves a new way for device design, thus expanding the research scope for 2D Te-based optoelectronics.

Magnetic polaron-related optical properties in Ni(II)-doped CdS nanobelts: Implication for spin nanophotonic devices

Emissions by magnetic polarons and spin-coupled d–d transitions in diluted magnetic semiconductors (DMSs) have become a popular research field due to their unusual optical behaviors. In this work, high-quality NiI2(II)-doped CdS nanobelts are synthesized via chemical vapor deposition (CVD), and then characterized by scanning electron microscopy (SEM), x-ray diffraction, x-ray photoelectron spectroscopy (XPS), and Raman scattering. At low temperatures, the photoluminescence (PL) spectra of the Ni-doped nanobelts demonstrate three peaks near the band edge: the free exciton (FX) peak, the exciton magnetic polaron (EMP) peak out of ferromagnetically coupled spins coupled with FXs, and a small higher-energy peak from the interaction of antiferromagnetic coupled Ni pairs and FXs, called antiferromagnetic magnetic polarons (AMPs). With a higher Ni doping concentration, in addition to the d–d transitions of single Ni ions at 620 nm and 760 nm, two other PL peaks appear at 530 nm and 685 nm, attributed to another EMP emission and the d–d transitions of the antiferromagnetic coupled Ni2+–Ni2+ pair, respectively. Furthermore, single-mode lasing at the first EMP is excited by a femtosecond laser pulse, proving a coherent bosonic lasing of the EMP condensate out of complicated states. These results show that the coupled spins play an important role in forming magnetic polaron and implementing related optical responses.

Modulation on Radiative Recombination Rate of CdS Nanobelts by Selective Rare Earth Ions

AbstractRare earth ions Er3+, La3+, and Y3+ have been introduced into the lattice of CdS nanobelts (NBs) to modulate its radiative recombination rate (RRR) during photoluminescence (PL) process. It is found that these ions have different quenching effects on the RRRs of direct interband transition and defect related transition. Only the former is greatly reduced through Er3+ doping, however, both of them are suppressed to a certain extent by La3+ and Y3+ doping. It is valuable that specific solid color luminescence can be realized through well‐chosen rare earth ions.

CdS nanobelt-based self-powered flexible photodetectors with high photosensitivity

Asymmetric contacts were used to assemble extremely photosensitive and self-powered photodetectors (SPDs) on rigid and polyimide (PI) substrates based on one-dimensional (1D)-CdS nanobelts.

In-situ modal inspection based on transverse second harmonic generation in single CdS nanobelt

Based on the transverse second-harmonic generation (TSHG) effect, we demonstrate a method for in-situ modal inspection of nonlinear micro/nanowaveguides. Pumping lights are equally split and coupled into two ends of a single CdS nanobelt (NB). As pumping light counter-propagates along the NB, transverse second-harmonic (TSH) interference patterns are observed. The influence of multimode interaction on the TSHG effect is discussed in detail. Using fast Fourier transform, TSH interference patterns are analyzed, indicating the existence of at least four modes inside the NB. Experimental beat lengths are found to be in agreement with calculated results.

Exposed (002) facets and controllable thickness of CdS nanobelts drive desirable hydrogen-adsorption free energy (ΔGH) for boosting visible-light photocatalytic performance

The strategies of exposed CdS (002) facets and controllable thickness lead to a desirable value for ΔGH, which can improve the CdS photocatalytic activity.

Preparation of ultrathin carbon-coated CdS nanobelts for advanced Li and Na storage

In this paper, we report a simple hydrothermal method for preparation of ultrathin carbon-coated CdS (CdS@C) nanobelts. The CdS@C nanobelts show superior electrochemical properties as an anode material for Li-ion batteries. The optimized CdS@C composites deliver a reversible capacity around 910 mAhg−1 and 48 mAhg−1 at 0.1 Ag−1 and 30.0 Ag−1, respectively. Moreover, the optimized nanobelts are also potential materials for Na storage. A stable capacity around 240 mAhg−1 is obtained at 0.1 Ag−1, even after 100 cycles.

Activation of infrared emission in (iodine, nickel) Co-Doped CdS nanobelts for solar cells and optoelectronic applications

Achieving tunable emission in semiconductors over a wide-spectral range has always remained a challenge for its potential applications. For this purpose, transition metals (TMs) have been widely doped into II-VI semiconductors, however, least efforts have been made on adding non-metals. Here, we co-doped non-metal and TM, i.e. iodine + nickel (I + Ni) into CdS 1D nanostructures and explored optical properties for the first time. FESEM shows that among CdS: (F + Ni, Cl + Ni, Br + Ni, I + Ni), I + Ni-doped CdS nanobelts (NBs) were thinner and have high crystallinity confirmed by XRD and Raman spectroscopy. Successful incorporation of iodine into CdS NBs was confirmed by EDX. Low temperature (80 K) photoluminescence (PL) of I + Ni doped CdS shows multiple emission centred at 525, 583, 758, and 916 nm, respectively. The first emission corresponds to exciton magnetic polaron (EMP) and the next two emissions correspond to d-d transition (3A2g → 1Eg) and (3T1P → 3T1F) of Ni ions, respectively. The last emission (916 nm) originated only in the I + Ni co-doped CdS NB which may correspond to the iodine incorporated into belts. According to the best knowledge, iodine related emission was detected for the first time. This work will promote their future applications in solar cells and optoelectronic devices.

CdS-decorated surface-coarsened TiO2 nanobelts with enhanced visible-light photocatalytic performances

Photodegradation of pollutants and photocatalytic hydrogen evolution of water splitting have been regarded as effective paths to solve the global environmental pollution and energy shortage. Herein, CdS-decorated surface-coarsened TiO2 nanobelts were fabricated by in-situ-deposited CdS on the surface-coarsened TiO2 nanobelts prepared by hydrothermal procedure followed by acid etched, and the visible-light photocatalytic performances were investigated. The as-synthesized composites presented multi-crystalline phase heterostructure with the specific surface of 64.368 m2 g−1 and the band gap of 2.22 eV. Owing to the synergic effect between CdS and surface-coarsened TiO2 nanobelts with multi-crystalline phase self-transformed heterostructure, the prepared composites showed effective separation of photogenerated carriers and excellent visible-light photocatalytic performances. Under visible-light irradiation, the degradation efficiency of methylene blue reached 99.7% with the photodegradation rate constant of 0.0231 min−1, and the average H2 evolution rate was 0.6225 mmol g−1 h−1 over 6 h. The visible-light photocatalytic activities of the as-prepared composites were greatly enhanced compared to CdS and CdS-decorated TiO2 nanobelts. The possible photodegradation mechanism was provided by investigating the active species.

Synthesis and characterization of CdS@ZnO nanoribbon@quantum dot and their enhanced visible-light-driven photocatalytic activities

CdS/ZnO nanoribbon/quantum dot was prepared using thermal decomposition method. Size and distribution of ZnO quantum dots on CdS nanobelt were controlled by concentrations of zinc acetate ethanol solution and thermal decomposition temperature. The structure and optical properties of CdS nanobelts and CdS/ZnO heterostructures are studied by XRD, TEM, PL and Raman scattering and UV–Vis absorption spectra. The photocatalytic performances of CdS nanobelts and CdS/ZnO heterostructures are tested by photocatalytic degradation of RhB aqueous solution under visible light irradiation. Compared with that (83.57%) of CdS nanobelts, the degradation rate (88.66%) of RhB using CdS/ZnO heterostructures as catalyst is significantly improved, which suggests better development prospect in photocatalytic technology and photoelectric device.

Mn(II) Ions Assisted Near-Infrared Single-Mode Lasing from an Individual Mn-Doped CdS Nanobelts

Tunable single-mode lasers are attractive for their potential applications in signal processing, optical communication, and displays. Here we present the Mn(II) ions assisted single-mode lasing occurring at near-infrared (NIR) band instead of the green emission band of CdS nanobelts (NBs) for the first time. Successful substation of Mn(II) ions at the tetrahedral Cd2+ cites in the CdS matrix were confirmed by EPR. Light Mn(II) doping (≤1%) in CdS belts not only red-shifted the Raman modes but also increased crystallinity compared to pure CdS NBs due to strong excitons-phonon couplings. Up to 3 µJ · cm-2 pumping fluence of ns laser, lightly doped CdS:Mn NBs show two photoluminescence (PL) emissions. First emission centered at 514.2 nm (green) corresponds to band-edge of CdS and an in-gap emission centered at 771.4 nm (NIR) corresponds to Mn(II) ions aggregates. After using intense excitation pulse, these NBs exhibited lasing at 791.4 nm with the lowest laser thresholds at 4.2 µJ · cm-2 in the CdS system. This lasing action is further confirmed by lifetime kinetics. The results indicated that the lasing in these NBs involves the localised excitons magnetic polarons and Farby-Perot (F-P) optical resonant processes at room temperature.

Phonon-Assisted Electro-Optical Switches and Logic Gates Based on Semiconductor Nanostructures.

High-performance nanostructured electro-optical switches and logic gates are highly desirable as essential building blocks in integrated photonics. In contrast to silicon-based optoelectronic devices, with their inherent indirect optical bandgap, weak light-modulation mechanism, and sophisticated device configuration, direct-bandgap-semiconductor nanostructures with attractive electro-optical properties are promising candidates for the construction of nanoscale optical switches for on-chip photonic integrations. However, previously reported semiconductor-nanostructure optical switches suffer from serious drawbacks such as high drive voltage, limited operation spectral range, and low modulation depth. High-efficiency electro-optical switches based on single CdS nanobelts with low drive voltage, ultra-high on/off ratio, and broad operation wavelength range, properties resulting from unique electric-field-dependent phonon-assisted optical transitions, are demonstrated. Furthermore, functional NOT, NOR, and NAND optical logic gates are demonstrated based on these switches. These switches and optical logic gates represent an important step toward integrated photonic circuits.

Crystal-Orientation-Related Dynamic Tuning of the Lasing Spectra of CdS Nanobelts by Piezoelectric Polarization.

Realizing dynamic wavelength tunability could bring about tremendous impacts in laser technology, pressure nanosensing, and lab-on-a-chip devices. Here, we demonstrate an original strategy to operate the lasing mode shift through reversible length changes of a CdS nanobelt, which is determined by the direction of piezoelectric polarization. The relationships between the direction of applied strain, the lasing mode shift, and the tunable effective refractive index are elaborated in detail. The correlation between the piezoelectric polarization-induced lasing mode red shift and the blue shift in the wavelength of the lasing mode output caused by the Poisson effect is discussed in depth, as well. Our study comprehensively considers the influence of both the cavity size variations and refractive index changes on the control of the lasing mode and provides a deeper understanding of the strain-induced lasing mode shift.

Enhancement-mode CdS nanobelts field effect transistors and phototransistors with HfO2 passivation

As typical direct bandgap II–VI semiconductors, quasi-one dimensional CdS nanowires, nanobelts, and nanorods have shown great potential in electronic and optoelectronic applications. However, most nano-scale CdS Field Effect Transistors (FETs) work in the depletion-mode (D-mode) due to the high unintentional n-type doping concentration, which results in high power consumption under off-state. In addition, the large dark current limits to the specific detectivity when they are fabricated into phototransistors. Here, we have synthesized single crystal CdS nanobelts (NBs) on a SiO2/Si substrate via chemical vapor deposition. The CdS NB FETs were fabricated with HfO2 as a passivation layer. It is found that the working mode of the FETs was transformed from the D-mode to the enhancement-mode with the threshold voltage changing from −22.6 to 0.7 V due to the decrease in the defect density. The HfO2 passivated CdS NB phototransistor shows a responsivity of 4.7 × 104 A/W and an ultrahigh detectivity of 9.07 × 1014 Jones at the source-drain voltage of 1 V under an illumination wavelength of 450 nm. Our work demonstrates an effective way to achieve enhancement-mode CdS FETs and high performance phototransistors.

Ultrahigh stress response and storage properties in a single CdS nanobelt-based flexible device for an erasable nonvolatile stress sensing and memory effect

A single CdS nanobelt with numerous stacking faults can not only show a giant response to compressive and tensile strains with excellent sensitivity, responsivity, and response and recovery speed, but also an erasable nonvolatile stress sensing and memory effect.