Structure Of SnS Research Articles

Metastable cubic tin sulfide: A novel phonon-stable chiral semiconductor

SnS is a semiconductor of interest for next-generation thin-film photovoltaic devices. The ground-state phase is layered with an orthorhombic (Pnma) crystal structure. Anisotropy in the electrical properties has been linked to the low performance of SnS solar cells. These factors make a new cubic phase (π-SnS) of immense practical interest. We report the properties of the recently solved crystal structure (P213) of cubic SnS from first-principles. π-SnS is phonon stable, in contrast to the zincblende phase, and lies 2.2 kJ/mol above the ground state. It features an electronic bandgap of 1.7 eV with a chiral modulation of the band-edge states.

Electronic structure of tin monosulfide

The band structure of three-dimensional and two-dimensional tin monosulfide was calculated by the density functional method in LDA and LDA+U approximations. Group-theoretical analysis of the electronic band structure of SnS crystallized in the orthorhombic structure with space group D2h16 – Pcmn is carried out, the symmetry of wave functions of the valence band and the bottom of the conduction band is found. The selection rules for direct and indirect optical transitions at different incident light polarization are determined. The group-theoretical analysis of energy states of the three-dimensional and two-dimensional SnS structures explains the formation of the band structure including the Davydov splitting. The calculated total density of states is compared with the known experimental XPS and UPS spectra, providing the assignment of their main features.

Electronic structures of SnS and SnS2

The electronic structures of SnS and SnS2 have been investigated from first principles calculations to provide a full analysis of the valence and conduction bands. A good agreement with experimental X‐ray photoelectron spectroscopy (XPS), S Kβ X‐ray emission spectroscopy (XES) and X‐ray absorption spectroscopy (XAS) at S K, Sn L1 and Sn L3 edges is found and the main features of the spectra are analysed in terms of chemical bonding. In the case of XAS, we show that core‐hole effect is significant at the S K edge. The origin of the 119Sn Mössbauer parameters has been also investigated. The increase of the isomer shift from SnS2 to SnS is related to the increase of Sn 5s electron population and correlated to the decreasing intensity of the lowest energy peak of the XAS spectra at the Sn L3 edge. The values of the quadrupole splitting evaluated from the electric field gradients at the nucleus are explained from the Sn 5p electron anisotropy. Finally, the effects of interlayer interactions and intralayer local distortion are examined by considering different structural models.

Bandgap engineering in semiconducting one to few layers of SnS and SnSe

Ab initio calculations on one, two, and three layers of SnS and SnSe compound semiconductors show that they all have indirect band gap similar to bulk and it varies in the range of ∼0.5–1.6 eV within the generalized gradient approximation due to quantum confinement as well as structural relaxations. In two‐dimensional structures, the difference between the direct and the indirect band gap is very low and in the case of a SnS bilayer, this difference is minimum. Further, the band gaps calculated with HSE06 functional are in good agreement with the experimental results available for bulk and single layer. The total and projected densities of states show that the top of the valence band arises from the hybridization of Sn 5s and chalcogen p valence orbitals while the bottom of the conduction band has predominantly Sn 5p character. The effective mass of electrons and holes are found to be small. These features are similar to the recently discovered perovskite materials for photovoltaics with high efficiency and suggest that SnS and SnSe layered materials are also promising for photovoltaics. Further calculations on bulk and layers of GeS and GeSe are reported and the results are compared with those of SnS and SnSe structures.

Ballistic Josephson junctions in the presence of generic spin dependent fields

Ballistic Josephson junctions are studied in the presence of a spin-splitting field and spin-orbit coupling. A generic expression for the quasiclassical Green's function is obtained and with its help we analyze several aspects of the proximity effect between a spin-textured normal metal (N) and singlet superconductors (S). In particular, we show that the density of states may show a zero-energy peak which is a generic consequence of the spin dependent couplings in heterostructures. In addition, we also obtain the spin current and the induced magnetic moment in a SNS structure and discuss possible coherent manipulation of the magnetization which results from the coupling between the superconducting phase and the spin degree of freedom. Our theory predicts a spin accumulation at the S/N interfaces, and transverse spin currents flowing perpendicular to the junction interfaces. Some of these findings can be understood in the light of a non-Abelian electrostatics.

A Study on Storytelling Structure of Image-based SNS

SNS는 개인의 미시적인 일상을 공유할 수 있는 스토리텔링 매체이다. 본 연구에서는 SNS가 텍스트 기반에서 이미지 기반의 형식으로 변화하고 있다는 점에 주목하고, 이미지 기반 SNS에 나타난 스토리텔링 구조를 밝히고자 한다. 이때 이미지와 해시태그(#)가 빈번하게 결합한다는 점에 주목하고 그 결합 양상을 분석한다. 이미지 기반 SNS에서 이미지는 다의적 의미로 해석될 수 있는 비결정적 사건이며, 해시태그는 이미지를 해석하는 기표가 된다. 특히 해시태그는 계열적 발산 운동을 통해 이미지에 대한 서사적 맥락을 생성하고, 이는 다시 수렴 운동을 통해 하나의 서사적 의미로 귀결한다. 이미지 기반 SNS는 이와 같은 이중 운동을 통해 서사적 구조를 획득한다. 본 연구에서는 이미지와 해시태그가 끊임없이 상호작용을 하면서 서사적 의미를 생성해낸다는 점에서 이미지 기반 SNS의 매체적 함의를 고찰한다.

Electron-Beam Induced Transformations of Layered Tin Dichalcogenides

By combining high-resolution transmission electron microscopy and associated analytical methods with first-principles calculations, we study the behavior of layered tin dichalcogenides under electron beam irradiation. We demonstrate that the controllable removal of chalcogen atoms due to electron irradiation, at both room and elevated temperatures, gives rise to transformations in the atomic structure of Sn-S and Sn-Se systems so that new phases with different properties can be induced. In particular, rhombohedral layered SnS2 and SnSe2 can be transformed via electron beam induced loss of chalcogen atoms into highly anisotropic orthorhombic layered SnS and SnSe. A striking dependence of the layer orientation of the resulting SnS-parallel to the layers of ultrathin SnS2 starting material, but slanted for transformations of thicker few-layer SnS2-is rationalized by a transformation pathway in which vacancies group into ordered S-vacancy lines, which convert via a Sn2S3 intermediate to SnS. Absence of a stable Sn2Se3 intermediate precludes this pathway for the selenides, hence SnSe2 always transforms into basal plane oriented SnSe. Our results provide microscopic insights into the transformation mechanism and show how irradiation can be used to tune the properties of layered tin chalcogenides for applications in electronics, catalysis, or energy storage.

Thermoelectric studies of IV–VI semiconductors for renewable energy resources

In the present study we explore the structural, electronic and thermoelectric properties of IV-VI semiconductors using first principle calculations based on the density functional theory. Generalized gradient approximation (GGA-PBEsol) is used as an exchange-correlation functional for the structural properties of the different crystal phases of these semiconductors. The compounds SnS, SnSe, GeS and GeSe favor orthorhombic structure, lead chalcogenides (PbS, PbSe and PbTe) are stable in the cubic rocksalt structure, while SnS2 and SnSe2 exist in hexagonal structure. For band structures additional to GGA, modified Becke and Johnson (mBJ) exchange potential is used. These compounds are narrow band gap semiconductors in the energy range 0.2–2.8eV. These binary IV-VI chalcogenides have direct band gap nature in cubic crystals while indirect in the orthorhombic phases. The post-DFT (BoltzTraP) calculations are performed to estimate Seebeck coefficient, electric and thermal conductivities, power factor and figure of merit of these compounds to check their applicability in thermoelectric devices. Spin orbit coupling effect influences the electronic and thermoelectric properties of these compounds due to the large size of the constituent elements. Further, the total thermal conductivity is computed using ad-hoc calculation with the experimental results. The calculated values of figure of merit for PbS, PbSe, PbTe and SnTe are in the range 0.68–0.77 at room temperature.

BilayerSnS2: Tunable stacking sequence by charging and loading pressure

Employing density functional theory-based methods, we investigate monolayer and bilayer structures of hexagonal SnS$_{2}$, which is recently synthesized monolayer metal dichalcogenide. Comparison of 1H and 1T phases of monolayer SnS$_{2}$ confirms the ground state to be the 1T phase. In its bilayer structure we examine different stacking configurations of the two layers. It is found that the interlayer coupling in bilayer SnS$_{2}$ is weaker than that of typical transition-metal dichalcogenides (TMDs) so that alternative stacking orders have similar structural parameters and they are separated with low energy barriers. Possible signature of the stacking order in SnS$_{2}$ bilayer has been sought in the calculated absorbance and reflectivity spectra. We also study the effects of the external electric field, charging, and loading pressure on the characteristic properties of bilayer SnS$_{2}$. It is found that (i) the electric field increases the coupling between the layers at its prefered stacking order, so the barrier height increases, (ii) the bang gap value can be tuned by the external E-field and under sufficient E-field, the bilayer SnS$_{2}$ can become semi-metal, (iii) the most favorable stacking order can be switched by charging and (iv) a loading pressure exceeding 3 GPa changes the stacking order. E-field tunable bandgap and easy-tunable stacking sequence of SnS$_{2}$ layers make this 2D crystal structure a good candidate for field effect transistor and nanoscale lubricant applications.

Electronic structure and optical properties of Fe-doped SnS2 from first-principle calculations

The Fe doping can increase the visible absorption of SnS2 and extend the absorption into the infrared region.

Ultrasmall SnS2nanoparticles anchored on well-distributed nitrogen-doped graphene sheets for Li-ion and Na-ion batteries

SnS2–NGS hybrid materials: ultrasmall SnS2–NGS hybrids have been first synthesized by a convenient annealing–hydrothermal-combined route. The excellent Li and Na storage ability is attributed to the unique structure of SnS2–NGS and the synergistic function between NGSs and SnS2.

Synergetic Effect of Yolk-Shell Structure and Uniform Mixing of SnS-MoS₂ Nanocrystals for Improved Na-Ion Storage Capabilities.

Mixed metal sulfide composite microspheres with a yolk-shell structure for sodium-ion batteries are studied. Tin-molybdenum oxide yolk-shell microspheres prepared by a one-pot spray pyrolysis process transform into yolk-shell SnS-MoS2 composite microspheres. The discharge capacities of the yolk-shell and dense-structured SnS-MoS2 composite microspheres for the 100th cycle are 396 and 207 mA h g(-1), and their capacity retentions measured from the second cycle are 89 and 47%, respectively. The yolk-shell SnS-MoS2 composite microspheres with high structural stability during repeated sodium insertion and desertion processes have low charge-transfer resistance even after long-term cycling. The synergetic effect of the yolk-shell structure and uniform mixing of the SnS and MoS2 nanocrystals result in the excellent sodium-ion storage properties of the yolk-shell SnS-MoS2 composite microspheres by improving their structural stability during cycling.

Quantized Energy Spectrum and Modified Andreev Bound States of a Superconductor with Generalized Uncertainty Principle

The effect of a minimal uncertainty in position or momentum measurement on a superconductor system is investigated. The Bogoliubov-de Gennes equations for the quasiparticle states in a linear potential are solved exactly, where the position and momenta are assumed to obey the modified commutation relations. It is found that the quantized energy spectrum of the superconductor could be induced by generalized uncertainty principle (GUP) directly. We also discuss the GUP-corrected Andreev bound states and supercurrent in a SNS structure. The results imply that the GUP effect in superconductor systems could be testable under present experimental condition.

Mechanical, electronic, and optical properties of the A4B6 layered ferroelectrics: ab initio calculation

AbstractWe have performed a first principles study of the structural, elastic and electronic properties of orthorhombic SnS and GeS compounds using the density functional theory within the local density approximation. The second‐order elastic constants have been calculated, and the other related quantities such as the Young's modulus, shear modulus, Poisson's ratio, anisotropy factor, sound velocities, Debye temperature, and hardness have also been estimated in the present work. All of the calculated modulus and Poisson's ratio for SnS were less than the same parameters for GeS. Our calculations have discovered the large anisotropy of elastic parameters in the (100) and (010)‐planes for both compounds. The band structures of orthorhombic SnS and GeS have been calculated along high symmetry directions in the first Brillouin zone (BZ). The calculation results for the band gap of Sn(Ge)S gave Eg = 0.256 eV (0.852 eV) and has an indirect character for an interband transition. The real and imaginary parts of dielectric functions and (by using these results) the optical constant such as energy‐loss function, the effective number of valance electrons and the effective optical dielectric constant were calculated. All of the principal features and singularities of the dielectric functions for both compounds were found in the energy region between 2 eV and 20 eV. (© 2015 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

PLD制备的Cu掺杂SnS薄膜的结构和光学特性

PLD制备的Cu掺杂SnS薄膜的结构和光学特性

Simple and Large Scale Synthesis of SnSX Nano-Belts, Flowers and Sheets for Li-Ion Battery Anode Applications

In this report, a variety of nanostructured materials of SnSx (such as nanobelts, nanoflowers and interconnected nanosheets) were prepared by hydrothermal synthesis method using mercaptopropionic acid (MPA) as the structure directing agent. By simply adjusting the amount of MPA in the precursor formulations and heating period, nanobelts, nanoflowers and interconnected nanosheets of SnSx were obtained. The detailed growth processes of SnS2/SnS nanoflowers from nanobelts are elucidated. Morphological evolution of the definitively shaped SnSx nanostructures was followed by scanning electron microscopy. X-ray diffraction (XRD) analyses confirmed an orthorhombic crystal structure for SnS nanobelts. The XRD patterns of SnSx nanoflowers and interconnected nanosheets show a mixed phase comprising an orthorhombic crystal structure of SnS coupled with a hexagonal crystal structure of SnS2. The SnSx nanostructured materials demonstrated extremely large capacities when used as Li-ion battery anodes. Among the various anode nanostructures that we studied, the anode based on SnS2/SnS interconnected nanosheets showed an exceptionally high capacity. Initially it showed a reversible capacity of 800 mAh g-1 at a current density of 100 mA g-1 and even after 50 cycles it retained a capacity of 470 mAh g-1 with almost 97% Coulombic efficiency. The SnS2/SnS interconnected nanosheets also exhibited an excellent rate capability even at a very high current density (1160 mA g-1) a charge capacity of 360 mAh g-1 was obtained. We demonstrate that this facile hydrothermal route assisted by MPA adopted herein for the development of SnSx based high performance anodes is also extendable to other potential inorganic anode materials.

Development of SnS Thin Films for Solar Cells

SnS thin film, a potential earth-abundant photovoltaic material, has particularly generated interest because of its nontoxic nature, the band gap of it matches well with solar spectrum and its high absorption coefficient. It provides a brief description of the development of SnS thin film for solar cells, and surveys several preparation methods of SnS thin film, then introduces the crystal structure of SnS. The effects of different doping elements and concentrations for SnS thin film on performance were outlined, and the development and the structure of solar cells based on SnS thin films were discussed. Finally, the development tendency and prospects were predicted.

Quantum confinement effect on electronic and optical properties of SnS

The structural stabilities, electronic and optical properties of SnS bulk, monolayer, and multilayers are systematically studied by using the first-principles calculations within the density-functional theory. Our calculated results indicate that monolayer SnS can be exfoliated from its bulk, and the process is similar to the fabrication of graphene. With the reduction of layer number, the structural stabilities of SnS nanostructures become weak and their band gaps increase due to the quantum confinement effect and the layer interactions. Therefore, the optical properties of SnS can be controlled by adjusting the layer number due to the fact that the optical properties of materials depend on their electronic structures. The main optical absorption peaks of SnS bulk and nanostructures originate from the electron transitions among the orbitals of Sn-5s, 5p and S-2p. Moreover, the optical absorption peaks of SnS show obvious blue shift when SnS structure transforms from its bulk to monolayer. The present study will contribute to the application of SnS materials in the solar cells.

Low Temperature Chemical Synthesis of p-Type SnS Thin Films Suitable for Photovoltaic Structures

SnS thin film has been deposited on glass substrate at room temperature using low cost, environmental friendly chemical bath deposition (CBD) technique. The structural parameters of the deposited film have been investigated through X- ray diffraction measurements. The deposited SnS film found almost crystalline with preferred orientations along (111) planes revealing an orthorhombic phase of herzenbergite SnS structure. The lattice parameters and dislocation density were determined. The average grain size estimated to be ~ 25 nm. The surface morphology of the film examined using scanning electron microscopy (SEM) show uniform granular and any crack or pinhole free deposition of the film. The chemical compositions of the film examined using energy dispersive analysis of x-rays (EDAX) confirmed stoichiometric deposition. The analysis of the optical absorption spectra of the deposited film in the wavelength range of 200-1200 nm indicate that direct allowed transitions are dominant in the film. The direct band gap of the film determined to be ~ 1.92 eV which is higher than those reported earlier for bulk or single crystal SnS, exhibiting quantum size effect at the observed grain size in the film. This value of band gap is promising for possible use of the deposited film as absorption layer in photovoltaic structures like solar cells. The thermoelectric power measurements indicate p-type electrical conductivity of the deposited films. A systematic study on room temperature chemical deposition and characterization of SnS thin films suitable for absorber layer in photovoltaic structures has been reported.

Optoelectronic properties of single-layer, double-layer, and bulk tin sulfide: A theoretical study

SnS is a metal monochalcogenide suitable for use as absorber material in thin film photovoltaic cells. Its structure is an orthorhombic crystal of weakly coupled layers, each layer consisting of strongly bonded Sn-S units. We use first-principles calculations to study model single-layer, double-layer, and bulk structures of SnS in order to elucidate its electronic structure. We find that the optoelectronic properties of the material can vary significantly with respect to the number of layers and the separation between them: the calculated band gap is wider for fewer layers (2.72 eV, 1.57 eV, and 1.07 eV for single-layer, double-layer, and bulk SnS, respectively) and increases with tensile strain along the layer stacking direction (by ∼55 meV/1% strain).