Bulk SnS Research Articles

Observation of voltage dependent negative differential resistance (NDR) in SnS2-GO nanocomposites

This study investigates the structural, optical, and electrical properties of tin disulfide (SnS2) and SnS2-graphene oxide (GO) nanosheets synthesized via chemical bath deposition method (CBD). Structural characterization confirms the formation of hexagonal crystal phases with nanosheet morphology. It shows a well distribution of nanosheet average square sizes of 10 nm for SnS2 and 6 nm for SnS2-GO. Optical analysis shows blue shifts in absorption edges compared to bulk SnS2, attributed to quantum confinement effects. Photoluminescence emission peaks exhibit different energy levels in SnS2-GO originated to native defects. The composites show a sharp reduced of PL intensity due to enhanced charge carrier separation. Electrical measurements on SnS2-GO thin films demonstrate negative differential resistance (NDR) behavior in both planar and sandwich contact configurations, suggesting electron injection/extraction mechanisms. The NDR phenomenon exhibits a dependence on voltage scan rate, indicating the involvement of electronic and ionic elements in charge transport mechanisms. Overall, this study provides insights into the NDR properties of SnS2-GO nanocomposite, laying the groundwork for their potential applications in optoelectronics and nanoelectronics.

Interlayer expanded SnS/N-doped carbon/SnS ultra-thin composite driven from layered tin chalcogenides as advanced anode for lithium and sodium ion battery

The unique 2D-layered structure of tin (II) sulfide (SnS) compounds has led to the emergence of strong intensities, showcasing their significant potential in lithium (LIBs) and sodium (SIBs) ion batteries. However, the commercialization process of SnS compounds remain hindered due to the poor cycle stability caused by its substantial volume expansion during cycling in battery applications. In this study, a simple and scalable synthesis of ultra-thin composite with a well-connected structure SnS/N-doped carbon/SnS (SnS/NC/SnS) is reported. The structure is directly derived from layered tin chalcogenides (A2Sn3S7·xH2O, where A represents an organic cation). Within this configuration, SnS nanosheets are decorated on the N-doped carbon material. The composite exhibits an expanded layer of 9.7 Å, enabling rapid movement of Na+ ions (approximately 7 times the diffusion coefficient of bulk SnS). This expansion also aids in accommodating volume changes during the discharging and charging processes. Concurrently, theoretical calculations demonstrate that the structure maintains a relatively stable state at the interlayer spacing mentioned. The SnS/NC/SnS composite material exhibited significant potential for application in both SIBs and LIBs. In SIBs, it demonstrated excellent long-term cyclic stability, maintaining a capacity of 190 mA h g−1 even under high current density conditions of 2.5 A g−1 after 300 cycles. In LIBs, it exhibit a superior discharge capacity of 990 mA h g−1 and retains 94.1 % of its capacity after 150 cycles at 0.2 A g−1. Notably, this synthesis method is versatile, as the interlayer spacing can be adjusted by varying the type of organic cations used in the process.

Large-Scale Production and Optical Properties of a High-Quality SnS2 Single Crystal Grown Using the Chemical Vapor Transportation Method

The scientific community believes that high-quality, bulk layered, semiconducting single crystals are crucial for producing two-dimensional (2D) nanosheets. This has a significant impact on current cutting-edge science in the development of next-generation electrical and optoelectronic devices. To meet this ever-increasing demand, efforts have been made to manufacture high-quality SnS2 single crystals utilizing low-cost CVT (chemical vapor transportation) technology, which allows for large-scale crystal production. Based on the chemical reaction that occurs throughout the CVT process, a viable mechanism for SnS2 growth is postulated in this paper. Optical, XRD with Le Bail fitting, TEM, and SEM are used to validate the quality, phase, gross structural/microstructural analyses, and morphology of SnS2 single crystals. Furthermore, Raman, TXRF, XPS, UV–Vis, and PL spectroscopy are used to corroborate the quality of the SnS2 single crystals, as well as the proposed energy level diagram for indirect transition in the bulk SnS2 single crystals. As a result, the suggested method provides a cost-effective method for growing high-quality SnS2 single crystals, which could lead to a new alternative resource for producing 2D SnS2 nanosheets, which are in great demand for designing next-generation optoelectronic and quantum devices.

Suppressed thermal conductivity of bilayer SnS: A comparative study among the monolayer, bilayer and bulk SnS

The layer-stacking of 2D materials have been proven to be an effective tool to modulate the low-dimensional electronic structures and transport properties. In this study, the lattice thermal transport properties of bilayer SnS are investigated systematically by solving phonon Boltzmann transport equation based on first-principles calculations. The stacking effect on the in-plane thermal conductivity is further revealed through comparing phonon transport properties of the monolayer, bilayer and bulk SnS. A dramatic suppression of the thermal conductivity, even below 0.5 Wm −1 K −1 per layer at 300 K, can be observed for the fully relaxed bilayer SnS, which implies the great potential for SnS-based thermoelectric applications. The underlying phonon transport mechanisms are also uncovered, and the drop of phonon relaxation time, resulted from the enhanced interlayer anharmonic phonon scattering, is responsible for the suppression of lattice thermal transport. • The stacking stability of bilayer SnS is revealed, and the AA′-stacking is the most dynamically stable configuration for the bilayer SnS. • A dramatically suppressed thermal conductivity for the special stacking configuration of the bilayer SnS, e. g. 0.294 (0.112) Wm −1 K −1 per layer at 300 K along the zigzag (armchair) direction, can be predicted. • The underlying phonon transport mechanisms, and the stacking effects, are also revealed through a comparative study among the monolayer, bilayer and bulk SnS.

Suppressed Thermal Conductivity of Bilayer Sns: A Comparative Study Among the Monolayer, Bilayer and Bulk Sns

Suppressed Thermal Conductivity of Bilayer Sns: A Comparative Study Among the Monolayer, Bilayer and Bulk Sns

Excitation dependent photoluminescence from quantum confined ultrasmall SnS sheets

Black phosphorus analogous tin(II) sulfide (SnS) has recently emerged as an attractive building block for photonic and optoelectronic devices due to its intrinsic anisotropic response. Two-dimensional SnS has shown to exhibit in-plane anisotropy in optical and electrical properties. However, the limitations in growing ultrasmall structures of SnS hinder the experimental exploration of anisotropic behavior in low dimension. Here, we present an elegant approach of synthesizing highly crystalline nanometer-sized SnS sheets. Ultrasmall SnS exhibits two distinct valleys along armchair and zig-zag directions due to in-plane structural anisotropy like bulk SnS. We find that in SnS nanosheets, the bandgaps corresponding to two valleys are increased due to the quantum confinement effect. Moreover, the photoluminescence (PL) from SnS quantum dots (QDs) is excitation energy dependent. Our spectroscopic studies infer that PL of SnS QDs originates from the two non-degenerate valleys.

Ultra-Sonication Assisted Synthesis of 2D SnS2 Nanoflakes for Room-Temperature No Gas Detection

Tin disulfide belongs to the class of layered materials and has drawn attention because of its unique surface properties. In this report, synthetically prepared bulk precursor has been used to fabricate 2D layered hexagonal SnS2 flakes by using liquid exfoliation technique. It was evident from structural and morphological characterization that the exfoliation produces aggregated flakes of SnS2. The prepared 2D SnS2 based sensor has shown a response toward NO gas at room temperature, whereas the bulk SnS2 based device doesn’t respond to any analyte. The device employing exfoliated SnS2 flakes as sensing layer responds to NO in the concentration range of 500 ppb (20.61%) to 2.75 ppm (163.32%). Moreover, the sensor offers highly stable and repeatable performance with little drift. This study implements an efficient route for nanoflakes synthesis from bulk layered SnS2 by the liquid exfoliation and the result of sensing test can stimulate in the production of high performance NO gas sensors.

Temperature dependence of the dielectric function and critical points of \u03b1-SnS from 27 to 350\xa0K

We report the temperature dependence of the dielectric function ε = ε1 + iε2 and critical point (CP) energies of biaxial α-SnS in the spectral energy region from 0.74 to 6.42 eV and temperatures from 27 to 350 K using spectroscopic ellipsometry. Bulk SnS was grown by temperature gradient method. Dielectric response functions were obtained using multilayer calculations to remove artifacts due to surface roughness. We observe sharpening and blue-shifting of CPs with decreasing temperature. A strong exciton effect is detected only in the armchair direction at low temperature. New CPs are observed at low temperature that cannot be detected at room temperature. The temperature dependences of the CP energies were determined by fitting the data to the phenomenological expression that contains the Bose–Einstein statistical factor and the temperature coefficient for describing the electron–phonon interaction.

Lateral Heterostructures of Multilayer GeS and SnS van der Waals Crystals.

Engineered heterostructures derive distinct properties from materials integration and interface formation. Two-dimensional crystals have been combined to form vertical stacks and lateral heterostuctures with covalent line interfaces. While thicker vertical stacks have been realized, lateral heterostructures from multilayer van der Waals crystals, which could bring the benefits of high-quality interfaces to bulk-like layered materials, have remained much less explored. Here, we demonstrate the integration of anisotropic layered Sn and Ge monosulfides into complex heterostructures with seamless lateral interfaces and tunable vertical design using a two-step growth process. The anisotropic lattice mismatch at the lateral interfaces between GeS and SnS is relaxed via dislocations and interfacial alloying. Nanoscale optoelectronic measurements by cathodoluminescence spectroscopy show the characteristic light emission of joined high-quality van der Waals crystals. Spectroscopy across the lateral interface indicates valley-selective luminescence in the bulk SnS component that arises due to anisotropic electron transfer across the interface. The results demonstrate the ability to realize high-quality lateral heterostructures of multilayer van der Waals crystals for diverse applications, e.g., in optoelectronics or valleytronics.

A polymer-assisted strategy for hierarchical SnS@N-doped carbon microspheres with enhanced lithium storage performance

Two-dimensional metal dichalcogenides show a promising potential in energy storage due to their high specific capacity. Different from the bulk SnS prepared by conventional solvothermal method, our strategy to prepare the three-dimensional (3D) hierarchical SnS@N-doped carbon (SnS@NC) microspheres assembled from ultrathin nanosheets is realized by the polymer-assisted solvothermal method. The key factor of SnS@NC microspheres is the use of polyvinylpyrrolidone, which not only acts as surfactant to obtain the hierarchical spherical structure but also is used as heteroatom sources to realize the N-doped carbon layer coating. Compared with the bulk SnS, the enhanced electrochemical performance of SnS@NC electrode can be attributed to its 3D hierarchical structure and composition advantages, including enhanced Li+ diffusion kinetics, faster charge transfer, enough void space to accommodate the volume variation, higher electronic conductivity, and more active sites.

Hollow spheres constructed by ultrathin SnS sheets for enhanced lithium storage

In this study, we report a hollow microsphere assembled by ultrathin SnS nanosheets prepared by a template method. Hollow ferroferric oxide (Fe3O4) spheres with abundant pores on the shell are used as templates, and SnS nanosheets can grow on the surface of the Fe3O4 shell. The key factor to obtain the unique structure of SnS sphere is the utilization of Fe3O4 template. When employed as the anode for lithium-ion battery, the SnS exhibits the better electrochemical performance than that of the bulk SnS electrode. With morphology observation and electrochemical impedance spectroscopy analysis, SnS/V-SnS electrodes are proved to possess several advantages, i.e., high specific surface area facilitates electrochemical reactions due to more active sites, shortened Li+ diffusion distance, and sufficient void space to sustain the volume change, which all contribute to its improved electrochemical performance.

Synthesis process and thermoelectric properties of the layered crystal structure SnS2

This work reports on the thermoelectric properties of bulk SnS2, which shows a similar composition and layered crystal structure to the extensively studied SnS and SnSe. The synthesis process for mechanical alloying (MA) SnS2 was also investigated. The SnS2 compound was formed in the reaction between SnS and S, after the formation of SnS using Sn and S as raw materials. However, single-phase SnS2 appears to be difficult to obtain by MA because Sn2S3 is produced when milling times are extended. Nevertheless, a pure-phase SnS2 bulk is achieved by further spark plasma sintering. The pristine SnS2 bulk shows an n-type conductive characteristic and a moderate absolute Seebeck coefficient between 100 and 700 μV/K. However, with a low figure of merit value ZT, the thermoelectric property is poor because of the low electrical conductivity of below 0.2 S/cm and the relatively high thermal conductivity of above 1.5 W/mK. Further, the electrical conductivity is enhanced and the thermal conductivity decreases significantly after Ag doping. An enhanced ZT value of 0.01 is achieved which is two times higher than pristine one.

Single crystal growth of bulk SnS2 and high yield preparation of few-layer SnS2

Abstract Two-dimensional layered SnS2 is attracting more and more attention due to its good electronic and optoelectronic properties. Herein, high yield and high quality SnS2 single crystals have been grown by chemical vapor transport method using muffle furnace instead of the traditional tube furnace. In addition, we report a modified mechanical exfoliation method, which is based on strong adhesion between gold decorated substrate and bulk SnS2, to produce high yield few-layered SnS2 with typical area size of nearly thousands of square microns. The electrical properties of FETs based on few-layered SnS2 further confirm the high quality of layered SnS2 with the carrier mobility of 2.8 cm2V−1s−1 and the current on/off ratio up to 105. It suggests that the exfoliation method introduced here provides an effective way to produce large-area, high-quality few-layered S n S 2 materials for future application.

Optical and structural-chemistry of SnS nanocrystals prepared by thermal decomposition of bis(N-di-isopropyl-N-octyl dithiocarbamato)tin(II) complex for promising materials in solar cell applications

Mixed ligand precursor complex bis(N-di-isopropyl-N-octyl dithiocarbamato)tin(II) complex was synthesized from its respective dithiocarbamate ligands, characterized and thermalized through thermogravimetric analysis to yield tin sulfide (SnS) nanocrystals. The thermal decomposition pattern was recorded as a function of the required temperature for the formation of the SnS nanocrystals at 360 °C. The SnS nanocrystals were characterized using optical, vibrational, structural and morphological analyses instruments. The obtained orthorhombic phase SnS nanocrystals showed indirect and direct optical energy band gaps close to the 1.5 eV of the bulk SnS.

Exploring structural stability mechanism of TiO2 encapsulated in 3D flower-like SnS2 anode for lithium ion batteries

SnS2 is considered as a promising anode material for lithium-ion batteries (LIBs) due to its high theoretical specific capacity, low toxicity, and low cost. However, its development has been hindered by the volume expansion/contraction during lithiation/delithiation process and also the poor electronic conductivity. Even TiO2 has been widely employed to improve the stability of the bulk SnS2, the underlying mechanism and its interaction with SnS2 remains unclear. Here, we synthesize two different kinds of SnS2/TiO2 heterojunctions with 3D ball-like structures (denoted as BST-1 and BST-2) assembled from nanosprindle and nanosphere TiO2 encapsulated in 3D SnS2 flowers, aiming to investigate their electrochemical performance and structural stability. Compared with pristine SnS2, the 3D BST-1 and BST-2 demonstrate high specific capacity, remarkable rate capability and cycling stability. Ex-situ X-ray diffraction shows that four phase transitions occur to pure SnS2 during charge and discharge process whereas only two to BST-1 and BST-2. We attribute the difference to rapid ion transports introduced by in-situ lithiating TiO2, which helps stabilize the structure of SnS2.

Ferroelectricity and piezoelectricity in monolayers and nanoplatelets of SnS

The ground-state structure of monolayers and nanoplatelets of SnS with a thickness from two to five monolayers is calculated from first principles. It is shown that nanoobjects with only an odd number of monolayers are ferroelectric. The ferroelectric, piezoelectric, and elastic properties of these polar structures are calculated. The appearance of polarization in these nanoobjects is explained by an uncompensated polarization that exists in an antiferroelectric structure of bulk SnS. The mechanism of ferroelectricity, in which the ferroelectric distortion is associated with short-range ordering of lone pairs, can be regarded as a way of creating ferroelectrics with high Curie temperature.

Surface plasmon resonance induced enhancement of photoluminescence and Raman line intensity in SnS quantum dot-Sn nanoparticle hybrid structure

In this article, we report on enhancement in photoluminescence and Raman line intensity of SnS quantum dots embedded in a mesh of Sn nanostructures. SnS nanoparticles synthesized by homogenous precipitation method show strong quantum confinement with a band gap of ∼2.7 eV (blue shift of ∼1 eV compared to bulk SnS particles). The optical band gap of SnS quantum dots is controlled by varying the pH (∼0 to 2.25), ageing time (24 to 144 h) and molarity (0 to 2 M) of the precursors. These SnS nanoparticles are embedded in a mesh of Sn nanostructures which are synthesized from tin chloride by using sodium borohydride as reducing agent. The Sn nanostructures have a morphology dependent, tunable surface plasmon resonance (SPR), ranging from UV (∼295 nm) to visible region (∼400 nm) of the electromagnetic spectrum. In the SnS-Sn nanohybrids, the excitons are strongly coupled with plasmons leading to a shift in the excitonic binding energy (∼400 meV). The pure SnS quantum dots have a very weak photoluminescence peak at ∼560 nm and Raman shift of low intensity at 853.08 cm−1, 1078.17 cm−1, 1255.60 cm−1, 1466.91 cm−1. The coupling of SnS nanoparticles with Sn nanoparticles results in strong exciton-plasmon interactions leading to enhanced photoluminescence and Raman line intensity. The nanohybrids formed using Sn nanosheets whose SPR matches with absorption onset of the SnS nanoparticles shows an enhancement of ∼104 times higher than pure SnS nanoparticles. Thus, Sn nanosheet with surface plasmon resonance in visible region (400 nm) like Au and Ag is a promising material for surface enhanced Raman spectroscopy, plasmon assisted fluorescence imaging and for enhancing the emission intensity of semiconductors with weak emission intensity.

Enhanced room-temperature NH3 gas sensing by 2D SnS2 with sulfur vacancies synthesized by chemical exfoliation

Recently, tin sulfide (SnS2) with different structures has been widely used for NH3 detection. However, the low sensitivity and high operating temperatures severely limit its potential application. Here, we demonstrate enhanced room temperature NH3 sensing using scalable SnS2 nanosheets, which are facily synthesized by chemical exfoliation. Structural and morphological characterization revealed that the as-prepared two-dimensional (2D) SnS2 is composed of 1–3 layers (0.6 nm–1.8 nm). Compared with the bulk SnS2 that shows none response to NH3, the gas sensors based on the as-prepared 2D SnS2 exhibit excellent ammonia gas sensing performance at room temperature. When exposed to 500 ppm ammonia, the response time, i.e., 16 s, is the shortest among all the NH3 gas sensors based on transition metal dichalcogenides (TMDs). We attribute this enhanced sensitivity mainly to the effective NH3 gas adsorption is dominated by the high energy defect sulfur vacancies on the surface of 2D SnS2. The easily synthesized 2D SnS2 with sulfur vacancies are expected to find a vast application in gas sensing.

Self-passivated ultra-thin SnS layers via mechanical exfoliation and post-oxidation.

Remarkable optical/electrical features are expected in two-dimensional group-IV monochalcogenides (MXs; M = Sn/Ge and X = S/Se) with a uniquely distorted layered structure. The lone pair electrons in the group-IV atoms are the origin of this structural distortion, while they also cause a strong interlayer force and high chemical reactivity. The fabrication of chemically stable few-to-monolayer MX has been a significant challenge. We have observed that, once the SnS surface is oxidized, the SnOx top layer works as a passivation layer for the SnS layer underneath. In this work, the SnOx/SnS hetero-structure is studied structurally, optically, and electrically. When tape-exfoliated bulk SnS is oxygen-annealed under a reduced pressure at 10 Pa, surface oxidation and SnS sublimation proceed simultaneously, resulting in a monolayer-thick SnS layer with the SnOx passivation layer. The field-effect transistor of nine-layer SnS prepared via mechanical exfoliation exhibits a p-type characteristic because of intrinsic Sn vacancies, whereas ambipolar behavior is observed for the monolayer-thick SnS obtained via oxygen annealing probably owing to the additional n-type doping by S vacancies. This work on monolayer-thick SnS fabrication can be applied to other unstable lone pair analogues and can facilitate future research on MXs.

Simple eco-friendly synthesis of the surfactant free SnS nanocrystal toward the photoelectrochemical cell application.

A simple, low cost, non-toxic and eco-friendly pathway for synthesizing efficient sunlight-driven tin sulfide photocatalyst was studied. SnS nanocrystals were prepared by using mechanical method. The bulk SnS was obtained by evaporation of SnS nanocrystal solution. The synthesized samples were characterized by using XRD, SEM, TEM, UV-vis, and Raman analyses. Well crystallized SnS nanocrystals were verified and the electrochemical characterization was also performed under visible light irradiation. The SnS nanocrystals have shown remarkable photocurrent density of 7.6 mA cm−2 under 100 mW cm−2 which is about 10 times larger than that of the bulk SnS under notably stable operation conditions. Furthermore, the SnS nanocrystals presented higher stability than the bulk form. The IPCE(Incident photon to current conversion efficiency) of 9.3% at 420 nm was obtained for SnS nanocrystal photoanode which is strikingly higher than that of bulk SnS, 0.78%. This work suggests that the enhancement of reacting area by using SnS nanocrystal absorbers could give rise to the improvement of photoelectrochemical cell efficiency.