Tin Monosulfide Research Articles

The physical properties of SnS films grown on lattice‐matched and amorphous substrates

AbstractThe development of high‐quality tin monosulphide (SnS) layers is one of the crucial tasks in the fabrication of efficient SnS‐based optoelectronic devices. Reduction of strain between film and the substrate by using an appropriate lattice‐matched (LM) substrate is a new attempt for the growth of high‐quality layers. In this view, the SnS films were deposited on LM Al substrate using the thermal evaporation technique with a low rate of evaporation. The as‐grown SnS films were characterized using appropriate techniques and the obtained results are discussed by comparing them with the properties of SnS films grown on amorphous substrate under the same conditions. From structural analysis of the films, it is noticed that the SnS films deposited on amorphous substrate have crystallites that were oriented along different directions. However, the SnS crystallites grown on Al substrate exhibited epitaxial growth along the [101] direction. Photoluminescence (PL) and Raman studies reveal that the films grown on Al substrate have better optical properties than those of the films grown on amorphous substrates.

Temperature dependent structural properties of nanocrystalline SnS structures

This letter explores the structural behavior of nanocrystalline tin mono sulfide (SnS) structures with respect to temperature (100–600 K). These studies emphasize that the structural properties of SnS nanocrystalline structures depend on the surrounding temperature. The lattice parameters of SnS nanocrystals slightly varied like their microstructures with the increase of temperature. These changes strongly influence the optical properties of SnS nanostructures. On the other hand, the structures exhibited higher strain (∼0.44%) than that of microstructured (0.3%) and bulk (0.12%) counterparts. The observed results are discussed under the light of existing concepts and reported.

117Sn and 119Sn hyperfine structure in the rotational spectrum of tin monosulfide recorded using laser ablation-source equipped, chirped-pulse Fourier transform microwave spectroscopy

Tin metal has been ablated with pulsed radiation from a Nd:YAG laser (λ=1064 nm). Carbonyl sulfide, diluted in high pressure argon, has been pulsed into the resultant Sn plasma. One of the results of this experiment has been the production of SnS. These events have allowed a rotational spectrum of tin monosulfide to be studied using a chirped-pulse Fourier transform microwave spectrometer. The resolution of the spectrum obtained was sufficient to observe hyperfine structure from the 117Sn and 119Sn-containing SnS molecules. Tin nuclear spin-rotation hyperfine constants are reported for the first time.

Ultrasonically Assisted Synthesis of Tin Sulfide Nanorods at Room Temperature

A simple ultrasonic method was developed to synthesize rod-like SnS nanocrystals, using tin chloride and thioacetamide as starting materials, ethanolamine and water as solvents. The as-obtained nanostructures were characterized by X-ray diffraction (XRD) study, energy-dispersive X-ray spectroscopy (EDS), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and Ultraviolet-visible spectrophotometry (UV). From the XRD pattern, the reflection peaks of the as-obtained samples can be indexed to the orthorhombic structure with lattice constants a = 3.99, b = 4.34, c = 11.20 Å , which are very consistent with the values in the standard card of SnS phase (JCPDS No. 39-0354). No characteristic peak was observed for other impurities such as SnO2 and SnS2, implying the formation of single-phase tin monosulfide. The quantification calculation shows the ratio of Sn/S to be 51.30/48.70 via the EDS analysis. These data clearly indicate that the as-prepared rod-like nanostructures are exactly SnS. TEM results show that, the SnS nanorods have length about 100nm and width less than 30nm. The direct and indirect band gaps of the SnS nanorods are determined to be 1.53 eV and 1.34 eV, respectively. The band gaps of the as-obtained SnS nanorods showed blue shifts due to the quantum size effects. The ultrasonic condition is believed to be critical for the formation of SnS with pure phase. For it provides the energy to form rod-like nanostructures and helps preventing the hydrolysis of Sn2+ to form tin oxides and hydrates. Also, it prevents oxidation of the final products.

The application of SnS nanoparticles to bulk heterojunction solar cells

Tin mono-sulphide (SnS) nanoparticles were synthesized by a facile method. Reactions producing narrow size distribution SnS nanoparticles with the diameter of 5.0–10 nm were carried out in an ethylene glycol solution at 150 °C for 24 h. Bulk heterojunction solar cells with the structure of indium tin oxide (ITO)/polyethylenedioxythiophene:polystyrenesulphonate (PEDOT:PSS)/SnS:polymer/Al were fabricated by blending the nanoparticles with a conjugated polymer to form the active layer for the first time. Current density–voltage characterization of the devices showed that due to the addition of SnS nanoparticles to the polymer film, the device performance can be dramatically improved, compared with that of the pristine polymer solar cells.

Optimization of the distance between source and substrate for device-grade SnS filmsgrown by the thermal evaporation technique

Tin monosulfide (SnS) films with varying distance between the source and substrate(DSS) were prepared by the thermal evaporation technique at a temperature of300 °C to investigate the effect of the DSS on the physical properties. The physicalproperties of the as-deposited films are strongly influenced by the variation ofDSS. The thickness, Sn to S at.% ratio, grain size, and root mean square (rms)roughness of the films decreased with the increase of DSS. The films grown atDSS = 10 and 15 cm exhibited nearly single-crystalline nature with low electrical resistivity.From Hall-effect measurements, it is observed that the films grown atDSS≤15 cm havep-type conduction and the films grown at higher distances have n-type conduction due to the variation of theSn/S ratio. Thefilms grown at DSS = 15 cm showed higher optical band gap of 1.36 eV as compared with the films grown at otherdistances. The effect of the DSS on the physical properties of SnS films is discussed andreported.

Chemistry of delta-SnS: New Tin Monosulfide Polymorph Thin Films from Galvanostatic Electrodeposition

Galvanostatic deposition of tin monosulfide thin films (d-SnS phase) on transparent conductive glass was studied. Uniform films were deposited in aqueous baths with tartaric acid. Cyclic voltammetry suggested tin-tartrate complexes were crucial to film electrodeposition, suppressing tin metal reduction in favor of sulfur species reduction. X-ray diffraction showed primitive orthorhombic symmetry for d-SnS (a = 11.380 Aå, b= 4.029 Aå, c = 4.837 Aå). d-SnS was converted to a-SnS (a = 11.172 Aå, b = 3.994 Aå c = 4.311 Aå) following annealing at ~ 270 {degree sign}C in Ar(g). Characterization of the as-deposited films confirmed 1:1 Sn/S. The d-SnS structure was consistent over a range of deposition temperatures (50, 70, and 90 {degree sign}C). UV/Vis spectrometry confirmed increased disorder in films deposited at 50 {degree sign}C. A direct allowed optical band gap transition of lower energy for the d-SnS phase (1.05 eV) was obtained compared to that for a-SnS (direct, 1.2 eV).

The effect of substrate surface on the physical properties of SnS films

The effect of substrates on the physical properties of tin mono-sulphide (SnS) films has been studied. The SnS films were deposited using the resistive thermal evaporation method on CORNING 7059 glass, ITO-coated glass, Si wafer and Ag-coated glass substrates. The as-deposited films exhibited nearly stoichiometry between Sn and S elements with a Sn/S at.% ratio of ∼1.05. Structural analysis of these films indicated that the films are crystallized in the form of an orthorhombic crystalline structure and showed (1 1 1) as a dominant peak, except for the films grown on Si substrates. Si/SnS films exhibited (0 4 0) as a dominant peak. The ITO/SnS films showed high values of rms roughness (∼14.9 nm) and average grain size (∼225 nm), along with a low electrical resistivity of 8.9 × 10−3 Ω cm as compared to SnS films grown on glass, Si and Ag substrates. The ITO/SnS films exhibit low resistivity, probably due to the large size of grains, and could be suitable for optoelectronic device applications.

Influence of annealing on physical properties of evaporated SnS films

The effect of annealing on the composition, crystal structure, surface features and electro-optical properties of tin mono-sulfide (SnS) films, deposited by thermal evaporation at 300 °C, has been studied. Elemental analysis of the films shows sulfur deficiency, which increases at higher annealing temperatures (Ta). The SnS structure in the as-deposited and annealed films remains orthorhombic. With an increase in Ta, the grain size and the surface roughness are reduced. The electrical resistivity also decreases with increasing Ta. The variation of activation energy and optical parameters with Ta has been explained by taking into account the degree of preferred orientation of the grains. The films annealed at 100 °C show some unusual features compared to those annealed at other temperatures.

A simple synthesis of SnS nanoflakes at ambient conditions

The present work reports a simple route to prepare tin monosulfide semiconductor nanocrystals at ambient conditions. In the presence of complexant L-tartaric acid, SnCl2·2H2O was dissolved in ethylene glycol (EG) solution. After adjusting the solution pH value, sodium sulfide dissolved in EG was added into the solution. The solution changed from colorless into brown immediately and phase-pure SnS, which was confirmed by powder X-ray diffraction (XRD) was produced. The transmission electron microscopic (TEM) investigation shows very thin rectangular flake like SnS crystals of 10∼20 nm in size.

Shape-selected synthesis of nanocrystalline SnS in different alkaline media

Semiconducting Tin(II) monosulfide nanowires, nanorods and nanoparticles were successfully selectively prepared using SnCl2·2H2O and thiourea (Tu) as the raw materials by appropriately choosing different alkaline solution as reaction media. The SnS nanowires are uniform with diameters 30–70 nm and lengths 3–10 μm, the nanorods are about several micrometers long with average width of 60–200 nm and the nanoparticles have an even diameter of about 5–10 nm. Compared to the previous reports, the present method is relatively simple, without using complex apparatus, and manipulated conveniently, which may be favorable for industrial application in the future.

Atmospheric Pressure Chemical Vapor Deposition of Tin Sulfides (SnS, Sn2S3, and SnS2) on Glass

Atmospheric pressure chemical vapor deposition of SnS2, Sn2S3, and SnS has been achieved onto glass substrates from the reaction of SnCl4 with H2S at 300−545 °C. The films show good uniformity and surface coverage, adherence, and a variety of colors (black, yellow, brown, and gray) dependent on deposition temperature and film thickness. Growth rates were on the order of 1−2 μm min-1. All the films were crystalline. For substrate temperatures of up to 500 °C single phase films with the hexagonal SnS2 structure (a = 3.65(1) Å, c = 5.88(1) Å) were formed. At 525 °C a film of mixed composition containing predominantly orthorhombic Sn2S3 (a = 8.83(1) Å, b = 3.76(1) Å, c = 14.03(1) Å) was formed together with some SnS2. At 545 °C films with orthorhombic SnS structure (a = 4.30(1) Å, b = 11.20(1) Å, c = 3.99(1) Å) were formed. Scanning electron microscopy (SEM) revealed a variety of different film thicknesses and morphologies, including needles, plates, and ovoids, dependent on the deposition temperature and time. Energy-dispersive X-ray analysis (EDX) and electron probe measurements on the films indicated elemental ratios close to those for tin disulfide (SnS1.98), ditin trisulfide (SnS1.60), and tin monosulfide (SnS1.10) and revealed no incorporation of chlorine. X-ray photoelectron spectroscopy (XPS) gave results in agreement with those from EDX and revealed binding energies of Sn 3d5/2 = 486.5(1) eV and S 2p = 161.6(2) eV for films grown at less than 500 °C (SnS2), and Sn 3d5/2 = 485.7 (1) eV and S 2p3/2 = 161.0 eV for the film grown at 545 °C (SnS). Raman microscopy showed that the films of SnS2 had bands at 315 and 215 cm-1, those of Sn2S3 had bands at 307, 251, 234, 183, 71, 60, and 52 cm-1, and those of SnS had bands at 288, 220, 189, 163, and 96 cm-1. The band gap of SnS2 was 2.14 eV. Sheet resistance measurements showed that all of the films were essentially insulating.

The structural behaviour of layers of SnS grown by spraypyrolysis

Thin layers of tin monosulphide have been grown from equimolar solutions of tin chloride and N,N-dimethyl thiourea on Corning 7059 glass substrates at various temperatures in the range 100-450 °C using spray pyrolysis. The structural properties have been determined by using x-ray diffraction and scanning electron microscopy to evaluate the crystalline phases present and the surface topography of the grown layers. The changes observed in the structural phases with the growth temperature during the film formation are reported and discussed.

Growth of polycrystalline SnS films by spray pyrolysis

Thin films of tin monosulfide (SnS) have been prepared by spray pyrolysis on Corning 7059 glass substrates with the substrate temperatures in the range 300–350°C, keeping the other deposition parameters constant. The films were characterised to evaluate the composition, structure, electrical resistivity and optical energy gap.

Diode-laser measurement of the infrared spectrum of tin monosulfide

The infrared spectra of seven isotopic forms of tin monosulfide in natural abundance ( 120Sn 32S: 31.2%, 118Sn 32S: 22.8%, 116Sn 32S: 13.6%, 119Sn 32S: 8.2%, 117Sn 32S: 7.2%, 124Sn 32S: 5.6%, 122Sn 32S: 4.5%) In their ground electronic states ( 1Σ) have been measured using a diode-laser spectrometer. An accurate set of Dunham parameters, mass-independent parameters and mass-scaling coefficients were calculated. The coefficients of the Dunham potential of SnS were also accurately determined using a direct fitting procedure.

Optical constants of tin monosulphide single crystals in the transparency region

The transmittance and reflectance of single crystals of tin monosulphide were measured at normal incidence from which values the absorption coefficient was calculated. The refractive index, n, of a SnS single crystal was measured by the prism method in the transparency region. The extinction coefficient, k, was calculated from the absorption coefficient. Measurements were performed at room temperature using plane-polarised light with the plane of polarisation parallel to either the a or b crystallographic axis, both of which lie in the plane of cleavage. The real and imaginary parts of the complex dielectric constant ( epsilon r, epsilon i) as well as the reflectance and its phase change (R, Phi ) were calculated from the values of n and k. It was shown that the SnS single crystal exhibits birefringence. Assuming that SnS binding is partly ionic and partly covalent, the optical constants were satisfactorily fitted to the model of a single effective oscillator.

Photoelectrochemical behaviour of tin monosulphide

Polycrystalline samples of tin monosulphide were prepared by passing H 2S through an acidic solution of stannous chloride. The structure and the composition of the samples were confirmed by X-ray diffraction and energy dispersive analysis of X-rays. Hall measurements showed the samples to be n type and the mobility of the majority carriers was found to be 11.4 cm 2 V −1 s −1. Reflectance spectra of the powder samples indicated a band gap of 1.29 eV. The photoelectrochemical behaviour of n-SnS was studied in Fe 3+/Fe 2+, Ce 4+/Ce 3+ and I 2/I − redox couples. Capacitance measurements yielded a donor density equal to 1.26 × 10 16 cm −3, which is in agreement with the value 2.28 × 10 16 cm −3 obtained from Hall measurements. Cyclic voltammetric studies on platinum as well as n-SnS were carried out with the best suitable Ce 4+/Ce 3+ redox couple and the onset potential (+0.46 V vs. a saturated calomel electrode (SCE)) was found to be in good agreement with the value of the flat-band potential obtained from impedance measurements. The semiconductor was found to be stable against photocorrosion in the Ce 4+/Ce 3+ redox couple over a period of 60 h. A photoconversion efficiency of 0.63% was obtained with the cell n-SnS/Ce 4+, Ce 3+/Pt. The photoelectrochemical studies were carried out with a tungsten-halogen lamp and with solar radiation. Both illuminations gave similar results.

Some Electrical and Optical Properties of Tin Monosulphide

Some Electrical and Optical Properties of Tin Monosulphide