SbSI Crystals Research Articles

One-dimensional SbSI crystals from Sb, S, and I mixtures in ethylene glycol for solar energy harvesting

Crystalline SbSI nanorods were synthesized using mixed sonication-heating route using a high boiling solvent (ethylene glycol—EG). The use of a high boiling solvent reveals that the temperature is responsible for self-assembly of amorphous SbSI nuclei to 1D crystal. X-ray diffraction analysis of this material showed that 1D SbSI was single crystalline and grows along c-direction of its orthorhombic structure. The elemental composition of SbSI nanorods was estimated by EDXS and was found to be with 33.92% Sb, 32.74% S, and 33.34% I. The optical bandgap of the material was 1.88 eV. Application of SbSI as a photon-absorbing material in a carbon-based solar cell has been assessed. Its photo-conversion efficiency was of 0.035% under simulated solar radiation, with a short-circuit current density of 0.4 mA/cm2 and open-circuit voltage of 290 mV.

Effect of strain on the Curie temperature and band structure of low-dimensional SbSI

Photoferroelectric materials show great promise for developing alternative photovoltaics and photovoltaic-type non-volatile memories. However, the localized nature of the d orbital and large bandgap of most natural photoferroelectric materials lead to low electron/hole mobility and limit the realization of technologically practical devices. Antimony sulpho-iodide (SbSI) is a photoferroelectric material which is expected to have high electron/hole mobility in the ferroelectric state due to its non-local band dispersion and narrow bandgap. However, SbSI exhibits the paraelectric state close to room temperature. In this report, as a proof of concept, we explore the possibility to stabilize the SbSI ferroelectric phase above room temperature via mechanical strain engineering. We synthesized thin low-dimensional crystals of SbSI by chemical vapor deposition, confirmed its crystal structure with electron diffraction, studied its optical properties via photoluminescence spectroscopy and time-resolved photoluminescence spectroscopy, and probed its phase transition using temperature-dependent steady-state photoluminescence spectroscopy. We found that introducing external mechanical strain to these low-dimensional crystals may lead to an increase in their Curie temperature (by ∼60 K), derived by the strain-modified optical phase transition in SbSI and quantified by Kern formulation and Landau theory. The study suggests that strain engineering could be an effective way to stabilize the ferroelectric phase of SbSI at above room temperature, providing a solution enabling its application for technologically useful photoferroelectric devices.

First-principles study of the structural, elastic and electronic properties of SbXI (X=S, Se, Te) crystals.

The structural, elastic, elastic anisotropy and electronic properties of ferroelectric SbSI and paraelectric SbSI, SbSeI and SbTeI crystals were computed using the local density approximation with first-principle calculations, based on density functional theory. The independent elastic constants of SbXI compounds were computed and the results reveal that they are mechanically stable. Some polycrystalline quantities such as bulk modulus, shear modulus, acoustic velocities, Young's modulus, Poisson's ratio, elastic anisotropy and elastic Debye temperatures of these compounds were derived from computed elastic constants. Energy band structures show that these compounds have an indirect band gap. The electronic charge distribution and partial density of states of SbXI compounds indicate that the Sb-X bond is typically covalent with a strong hybridization as well as Sb-I compounds that have strong ionic character. The results obtained were compared with experimentally measured values and other theoretical data.

Birefringence of SbSI and SbSeI crystals at the region of antiferroelectric phase transition

ABSTRACTAnomalous behavior has been observed in the temperature range of T = 140–145 °C. The electric current I(T) of SbSI and SbSeI crystals along the c(z) axis changes significantly at the region of the antiferroelectric phase transition when DC voltage is applied. The peak positions are observed at 140 °C and 145 °C for SbSI and SbSeI, respectively. The birefringence spectra show temperature-dependent changes upon retardation m, confirming the antiferroelectric phase transition for both crystals. The peak positions observed from the optical measurements do not differ from the electrical measurements, showing the transition point at 140 °C and 145 °C for SbSI and SbSeI, respectively.

Water-based ultrasonic synthesis of SbSI nanoneedles

Semiconducting nanomaterials have found a range of applications in optoelectronics, energy harvesting, sensing, bio-imaging etc. Nanomaterials should be easy and inexpensive to manufacture, with stable and reproducible characteristics over time. Antimony sulpho-iodide (SbSI) has a unique combination of semiconductor, optic and piezoelectric parameters, however, its applications are currently hampered by difficulties in its production. Previous studies and experiments carried out to synthesize SbSI crystals involved long reaction times (over 70h), and high temperatures (≈250°C).In this work we developed water-based synthesis to produce sub-micro sized crystals and explore their properties. We attempted to control SbSI particles growth and formation by adding different surfactants and fillers to the reaction system. The crystal dimensions (shape/size) varied depending on the added filler. In addition, we performed in vitro cytotoxicity studies of SbSI particles and evaluated their potential for biomedical applications.

Dielectric and electrical properties of SbSI and SbSeI single crystals in the region of antiferroelectric phase transition

Experimental results have shown that the capacitance (dielectric permittivity) and electrical conductivity of SbSI and SbSeI crystals along the c(z)-axis change significantly in the region of the antiferroelectric phase transition when DC voltage is applied. An electric field changes the form of B1u (A1) soft mode potential in sites of Sb atoms, which turns the antiferroelectric phase into an induced ferroelectric phase. Degenerate energy levels then split into non-degenerate levels due to electron–phonon interaction (pseudo Jahn–Teller effect), while a narrowed band gap simultaneously creates strong and abrupt changes in C(T) and σ(T).

Growth of large SbSI crystals

Abstract In this paper a novel method of SbSI single crystals fabrication is presented. In this method a sonochemically prepared SbSI gel is used as an intermediate product in a vapour growth process. The main advantages of the presented technique are as follows. First, the SbSI gel source material has lower temperature of sublimation and allows to avoid explosions during SbSI synthesis (the sonochemical synthesis is free of any explosion hazard). Second, but not least, the grown SbSI single crystals have smaller ratio of longitudinal and lateral dimensions. The cross sections of the presented crystals are relatively large (they are up to 9 mm2). The crystals have been characterized by X-ray diffraction, angle-resolved optical spectroscopy, and diffusive reflectivity.

Dielectric Properties of SbSI in the Temperature Range of 292-475~K

The antimony sulfoiodide (SbSI) is the most outstanding representative of ferroelectricsemiconductors that show interesting physical properties (optical, photoconducting, ferroelectric, piezoelectric, etc.) and have drawn the attention of numerous investigators. Recently, SbSI has been used to construct nanosensors of humidity [1-3] as well as photonic crystals [4]. It seems very promising to investigate the sensing and photonic properties of such devices near phase transition points. This work presents results of measurements of impedance and ferroelectric histeresis loops in single crystals of SbSI grown from the vapour phase. The measurements were performed in the temperature range of 292-475 K. In contrary to the recently published data [5] of the SbSI crystals grown by the Bridgman-Stockbarger technique no evidence of antiferroelectric phase transition near 410 K has been observed. The methodology of the impedance measurements is discussed, too.

Synthesis of Antimony Sulphoiodide by CVD and its Characterization

Antimony Sulphoiodide is most widely studied compound in group V-VI-VII family due to its largenumber of properties. Varoius methods of synthesis have been reported. We are the first to reportsynthesis of shiny SbSI crystals by the Chemical Vapor Deposition (CVD) technique using powder ofAntimony, Sulphur and Iodine as the starting material. Needle shaped thin crystals of SbSI were foundgrown vertically on the walls of the quartz tube. Characterizations of the sample were done usingdifferent techniques such as powder X-ray diffraction (XRD), scanning electron microscopy (SEM)and energy dispersive X-ray analysis (EDAX). The charcteristcs peaks in Raman scattering plots (0-500 cm-1) match with the reported results. The compound exibits high resitivity at room temperaturein the order of 10-7 Ω-cm and dielectric constant in the order of 10-3 measured at 1 KHz.DOI: http://dx.doi.org/10.3126/jncs.v30i0.9381Journal of Nepal Chemical Society Vol. 30, 2012 Page: 111-117 Uploaded date: 12/20/2013

Structural, thermodynamic and phonon properties of SbSI and SbSBr single crystals

The structural, dynamical and thermodynamic properties of antimony sulfoiodide (SbSI) and antimony sulfobromide (SbSBr) are investigated by using an ab-initio pseudopotential method applying density functional theory (DFT) within the local density approximation (LDA). The dynamical properties, such as the phonon dispersion and the phonon density of states, are calculated. Making a factor group analysis we classify the phonon modes. Moreover, the thermodynamic properties, such as the entropy and the constant-volume specific heat, as functions of temperature and the phonon contribution to the free energy and the internal energy are calculated.

Origin of Ferroelectric Phase Transitions of BixSb1-xSI Mixed Crystals

The nature of normal modes’ anharmonism of SbSI—type crystals is investigated in this work. In order to explain the nature of anharmonism we apply the normal vibration mode's average potential energy's dependence on amplitudes of normal coordinates along c (z)—axis. It is proved that the variation of potential barrier between two wells of double-well potential energy Vp(z) is caused by temperature T, quasihidrostatic pressure p, and mixture x. The temperature dependence of ferroelectric phase transition on quasihidrostatic pressure p and mixture x is determined for SbSI and BixSb1-xSI crystals. Applying the equality is theoretically proved that there is no ferroelectric phase transition in BixSb1-xSI crystals where x > 0.7. The ferroelectric phase transition in SbSI—type crystals and BixSb1-xSI crystals is caused by the phonon interaction's dependence on temperature, pressure and mixture.

XPS analysis of sonochemically prepared SbSI ethanogel

This paper, for the first time, presents the results of the X-ray photoelectron spectroscopy (XPS) of the valence band and core levels in sonochemically prepared SbSI ethanogel consisting of nanowires. The XPS spectra were measured with monochromatized Al K α radiation in the energy range of 0–1400 eV at room temperature. It was found that the sonochemically prepared SbSI ethanogel is a p-type semiconductor. The XPS determined composition of this material suggests the existence of antimony subiodide at surfaces of SbSI nanowires. The chemical shifts in SbSI ethanogel for the Sb, I and S states are reported. Experimentally obtained binding energies are compared with the results reported for single crystals of SbSI.

Ferroelectric properties of ultrasonochemically prepared SbSI ethanogel

This article presents for the first time the electrical properties of sonochemically synthesised, high-surface-area SbSI ethanogel made up of large quantity nanowires with lateral dimensions of about 10–50 nm and lengths reaching up to several micrometers. The composition, morphology, dimensions, microstructures, and optical energy gap of the new form of SbSI were characterized. This material is a semiconducting ferroelectric as in the case of bulk SbSI crystals. The maximum of dielectric constant ε = 1.6 × 10 4 is observed at T c = 292(1) K. The activation energies in temperature dependences of electric conductivity of SbSI ethanogel are different for ferroelectric and paraelectric phases during heating and cooling of the sample.

Origin of the Optical Anomalies Near the Ferroelectric Phase Transition in SbSI and SbSBr Crystals

Experimental investigation of SbSI exponential absorption tail of slope σ/kT(T) and isoabsorption energy E K (T) at K = const reveal that in ferroelectric phase transition region at T c the slope σ/kT(T) has anomalous behavior. Explanation of this phenomena presented using electronic potential V(z) dependence upon high frequency mode B1u symmetry normal coordinates in (z) direction taking into account thermal fluctuations of the atoms in x − y plane. The splitting of B1u normal modes in double-well V(z) explains anomalous behavior σ/kT(T) at the ferroelectric phase transition region in SbSI and SbSBr crystals.

Antiferroelectric phase transition in SbSI and SbSeI crystals

This work represents existence of the high temperature antiferroelectric phase transitions in SbSI, SbSeI and BiSeI crystals. The antiferrolectric phase transition is found by a measured capacitance change at a frequency of 1 kHz for the SbSI and SbSeI crystals grown by the Bridgman–Stockbarger technique in the temperature range of 270–440 K. Therefore, SbSI has three phases: ferroelectric ( T < 295 K ), antiferroelectric ( 295 < T < 410 K ) and paraelectric ( T > 410 K ). SbSeI has two phases: antiferroelectric ( T < 410 K ) and paraelectric ( T > 410 K ). The antiferroelectric phase transition is of an intermediate type between displacive and order–disorder types.

Electronic structure of BiSeI clusters

The valence band (VB) energy levels of BiSeI crystals have been calculated and compared to the X-ray photoelectron spectra of SbSI crystals. A molecular cluster consisting of 20 molecules of BiSeI has been used to calculate the total VB density of states by the density functional theory (DFT) method. The spectrum of total VB density of states of the (BiSeI) 20 cluster weighted by atomic photoemission cross-sections has been compared with the experimental X-ray photoelectron VB spectrum of SbSI type crystals. The cluster model calculation has showed that the core level energy splitting depends on the difference of ionic charges of the same atoms at the edges of the (BiSeI) 20 cluster.

Infrared spectroscopy of ferroelectric nanowires of antimony sulfoiodide

For the first time the infrared absorbance of the ultrasonically fabricated nanowires of antimony sulfoiodide (SbSI) has been measured from 750cm−1 to 4000−1 cm. The SEM and HRTEM investigations exhibit that the as-prepared SbSI ethanogel is made up of large quantity nanowires with diameters of about 10–50nm and lengths reaching up to several μm and single-crystalline in nature. The IR measurements have been performed on as-prepared, dried and postannealed samples. The obtained results have been compared with the results of IR investigations of powdered single crystals of SbSI. One of the features of the sonochemically fabricated SbSI nanowires is the strong adsorption of ethanol, ethoxide species, ethylene and water.

The First Observation of the Tricritical Point in Ferroelectrics

The existence of Curie critical point (tricritical point in more recent terminology) was predicted by Landau in 1935. In 1945 Ginzburg created the phenomenological theory, of ferroelectricity based on Landau theory of the second order phase transitions. Ginzburg supposed, that ferroelectric phase transition of the first order in BaTiO 3 takes place in vicinity of the critical Curie point. This correct supposition could not be confirmed experimentally at this time and accordingly the Curie critical point coordinates could not be obtained because corresponding critical pressure for BaTiO 3 is more than 20 kbar. The first experimental observation of the critical (tricritical) point and estimation of its coordinates was performed in the ferroelectric SbSI crystals in 1967 and published next year. Later on, the tricritical point was found almost in the all ferroelectrics. This paper summarizes the results of experimental investigation of tricritical point in SbSI.

Theoretical Investigation of the Electronic Structure of Ferroelectric SbSBr Molecular Cluster

This paper presents the theoretical calculation of energy levels of the valence bands and bond orders of the SbSBr single crystals using the molecular cluster model consisting twenty SbSBr molecules. The theoretical calculation revealed that the ferroelectric phase transition changes the bond orders and shift valence bands. Results of theoretical calculations of averaged total density of states of SbSBr molecular cluster are compared with the experimentally results of X-ray photoelectron spectroscopy (XPS) of SbSI crystals, because that SbSI and SbSBr crystals have isomorphic electronic structure.

Investigation of the vibration spectrum of SbSI crystals in harmonic and in anharmonic approximations

The force constants of SbSI crystal have been calculated by the pseudo-potential method. The frequencies and normal coordinates of SbSI vibration modes along the c ( z) direction have been determined in harmonic approximation. The potential energies of SbSI normal modes dependence on normal coordinates along the c ( z) direction V( z) have been determined in anharmonic approximation, taking into account the interaction between the phonons. It has been found, that in the range of 30–120 cm −1, the vibrational spectrum is determined by a V( z) double-well normal mode, but in the range of 120–350 cm −1, it is determined by a V( z) single-well normal mode.