Photo-sensing properties of Cd-doped In2S3 thin films fabricated via low-cost nebulizer spray pyrolysis technique

In this study, we report the fabrication of cadmium-doped indium sulfide thin films (In₂S₃:Cd) using a low-cost nebulizer-aided spray pyrolysis process at 350 °C on glass substrates for photo-sensing applications. The impact of 0, 2, 4, and 8 wt% cadmium concentrations on the structure, morphology, optical properties, and photo-sensing capabilities of In₂S₃ thin films were examined systematically. From X-ray diffraction (XRD) analysis, the major peak is located in the (103) plane for all Cd-doped In₂S₃ thin film samples, and the maximum crystallite size for the 4 wt% sample is 59 nm. The field emission scanning electron microscope (FESEM) image revealed a homogenous large-grained surface of Cd-doped In₂S₃ film that completely covered the substrate. UV–Vis absorption analysis demonstrated good absorption for all thin film samples in the visible and ultraviolet regions of the electromagnetic spectrum, particularly, the 4% Cd-doped concentration showed excellent absorption as is observed from Tauc relation. The highest PL intensity at 680 nm was observed for the sample coated with 4 wt% of Cd. Under UV light, the I–V behavior depicts a light current of 1.06?×?10^–6 A for a 5 V bias voltage. The In₂S₃: Cd (4%) sample had the highest responsivity of 2.12?×?10^?1A/W and a detectivity of 1.84?×?10¹¹ Jones, with a high EQE of 50%. The study manifests that the developed Cd (4%)-doped In₂S₃ thin film sample might be better suited for the application of photodetectors.

     

Synthesis and photoluminescence of In2O3 nanocrystals and submicron crystals from InCl3•4H2O and thiourea

Two routes have been proposed for the synthesis of In₂O₃ powders from InCl₃•4H₂O and thiourea. One route involved a two-step procedure (that is, firstly, In₂S₃ clusters constructed with mainly nanoflakes were synthesized by heating the mixture of InCl₃•4H₂O and thiourea in air from room temperature to 200 °C, coupled with a subsequent washing treatment; secondly, In₂O₃ was obtained by calcining the In₂S₃ clusters in air at 600 °C for 6 h), and the other route was a one-step procedure (that is, In₂O₃ was synthesized directly by calcining the mixture of InCl₃•4H₂O and thiourea in air at 600 °C for 6 h). The resultant products were characterized by X-ray diffraction, energy dispersive X-ray spectroscopy, scanning electronic microscope and room temperature photoluminescence (RT-PL) spectra. It was observed that the In₂O₃ nanocrystals obtained via the two-step procedure exhibited PL peaks at about 453 and 471 nm, corresponding to the defeat-related emission; while the In₂O₃ submicron polyhedral crystals obtained via the one-step procedure and In₂O₃ pyramids obtained by calcining the only InCl₃•4H₂O in air at 600 °C for 6 h displayed a PL band centered at around 338 nm, corresponding to the band edge emission.     

Synthesis of heterostructured In2O3/BiOCl powders and their visible-light-driven photocatalytic activity for the degradation of Rhodamine B

Heterostructured In₂O₃/BiOCl powders were synthesized by chemical coprecipitation method at room temperature followed by thermal treatment at 400 °C for 2 h. The TEM results confirmed the formation of sheet-like BiOCl nanostructures with the thickness of ca. 5–7 nm. In order to investigate the effect of In₂O₃ on the photocatalytic activity of heterostructured powders, the amount of In₂O₃ was varied from 0 wt% to 14 wt%. Adsorption and photocatalytic activity of the samples were evaluated for the degradation of Rhodamine B (RhB) in the dark and under visible light irradiation, respectively. The heterostructured In₂O₃/BiOCl powders showed high adsorption capacity and enhanced photocatalytic activity compared to P25 and pure BiOCl. Based on the results obtained in this study, the mechanism for the enhancement of photocatalytic activity of heterostructured In₂O₃/BiOCl powders is discussed. 10 wt% In₂O₃/BiOCl composite also exhibited good cycle performance for the degradation of RhB under visible light irradiation.     

Thermal decomposition synthesis of 3D urchin-like α-Fe2O3 superstructures

Urchin-like α-Fe₂O₃ superstructures have been deposited on Si substrate using thermal decomposition FeCl₃ solution at 200–600 °C in the oven. The morphologies and structures of the synthesized urchin-like superstructures have been characterized by transmission electron microscopy (TEM), scanning electron microscopy (SEM), and X-ray diffraction (XRD). The results show that urchin-like α-Fe₂O₃ superstructures were a polycrystal with the rhombohedral structure and typical diameters of 16–20 nm and lengths up to 1.0 μm. The as-prepared α-Fe₂O₃ superstructures have a high Brunauer–Emmett–Teller (BET) surface area of about 60.24 m²/g. The photoluminescence spectrum of the urchin-like α-Fe₂O₃ superstructures consists of one weak emission peak at 548 nm (2.26 eV). A possible new mechanism for the formation of the urchin-like superstructures was also preliminarily discussed.     

Preparation and characterization of In2O3 nanorods

In₂O₃ nanorods were prepared by sol–gel technique with polyethylene octyl phenyl ther (OP-10) controlling their morphology and were characterized by TEM, TG-DSC and XRD. The results indicated that In₂O₃ nanorods had the length of about 120 nm and the diameter of about 20 nm. The precursor was In₂O(OH)₄ dry gelatin which was formed by partly dehydrating of In(OH)₃ molecules. The influencing factors and growth mechanism were discussed. The geometry arrangement parameter P of OP-10 was in 1/3–1/2 through calculating, which conformed the shape of claviform micelle.     

CuIn(S,Se)2 thin films prepared by selenization and sulfurization of sputtered Cu–In precursors

CuIn(S,Se)₂(CISSe) thin films have been prepared onto soda-lime-glass (SLG) substrates by selenization and sulfurization of magnetron sputtered Cu–In precursors. The results indicate that the properties of the CISSe films are strongly dependent on the post-annealing treatment. After annealing at 400 °C for 20 min, the CISSe films have formed tetragonal (chalcopyrite) crystal structure and the diffraction peaks of the films shift systematically to the left with the temperature varying from 400 °C to 500 °C. EDAX study reveals that the compositions of CISSe films are Cu_0.83In_1.17S_1.67Se_0.3, Cu_0.86In_1.13S_1.61Se_0.4 and Cu_0.82In_1.15S_1.54Se_0.49 after annealing at 400 °C, 450 °C and 500 °C, respectively. The direct optical band gaps of the films slightly decrease from 1.44 ev to 1.32 ev with the increase of the temperature from 400 °C to 500 °C, and the optical absorption coefficient is over 10⁵ cm⁻¹. The films annealed at 400 °C–500 °C are all found to be p-type and the resistivity is almost 10⁻²–10⁻³ Ω cm. The carrier mobility of the film at 500 °C is almost as high as 1.701 cm²/V S.     

Detection of H2S gas at lower operating temperature using sprayed nanostructured In2O3 thin films

Nanostructured indium oxide (In₂O₃) thin films were prepared by spray pyrolysis (SP) technique. X-ray diffraction (XRD) was used to investigate the structural properties and field emission scanning electron microscopy (FESEM) was used to confirm surface morphology of In₂O₃ films. Measurement of electrical conductivity and gas sensing performance were conducted using static gas sensing system. Gas sensing performance was studied at different operating temperature in the range of 25–150 °C for the gas concentration of 500 ppm. The maximum sensitivity (S = 79%) to H ₂ S was found at lower temperature of 50 °C. The quick response (4 s) and fast recovery (8 s) are the main features of this film.     

Crystallization process and electro-optical properties of In2O3 and ITO thin films

Amorphous indium oxide (In₂O₃) and 10-wt% SnO₂ doped In₂O₃ (ITO) thin films were prepared by pulsed-laser deposition. These films were crystallized upon heating in vacuum at an effective heating rate of 0.00847 °C/s, while the evolution of the structure was observed by in situ X-ray diffraction measurements. Fast crystallization of the films is observed in the temperature ranges 165–210 °C and 185–230 °C for the In₂O₃ and ITO films, respectively. The crystallization kinetics is described by a reaction equation, with activation energies of 2.31 ± 0.06 eV and 2.41 eV and order of reactions of 0.75 ± 0.07 and 0.75 for the In₂O₃ and ITO films, respectively. The structures of the films observed here during heating are compared with those obtained upon film growth at different temperatures. The resistivity of the films depends on the evolution of the structure, the oxygen content and the activation of tin dopants in the films. A low resistivity of 5.5 × 10⁻⁴ Ω cm was obtained for the In₂O₃ and ITO films at room temperature, after annealing to 250 °C the resistivity of the ITO film reduces to 1.2 × 10⁻⁴ Ω cm.     

CuSbS2 thin films by heating Sb2S3/Cu layers for PV applications

In this work, we present the preparation of CuSbS₂ thin films of approximately 850 nm in thickness by heating glass/Sb₂S₃/Cu layers in low vacuum and their application in PV structures: Glass/SnO₂:F/n-CdS/p-CuSbS₂/C/Ag. The Sb₂S₃ thin films were chemically deposited from a solution containing SbCl₃ and Na₂S₂O₃ at 40 °C on well cleaned substrates. Copper thin films of 50 nm were thermally evaporated on Sb₂S₃ films of thickness ~600 and 800 nm and the glass/Sb₂S₃/Cu precursor layers were heated in vacuum at 300 and 350 °C for 1 h. Structural, morphological, optical and electrical characterizations of the annealed thin films were analyzed by X-ray diffraction, Atomic force microscopy, UV–Vis spectrometry and photoresponse measurements. Studies on identification and chemical state of the elements were done using X-ray photoelectron spectroscopy. Photovoltaic devices were prepared using CuSbS₂ thin films as absorber and chemical bath deposited CdS thin films as window layer on FTO coated glass substrates. The photovoltaic parameters of the devices were evaluated from the corresponding J–V curves, yielding J_sc, V_oc and FF values in the range of 1.03–1.55 mA/cm², 250–294 mV and 0.46–0.57 respectively, performed using a solar simulator under illumination of AM1.5 radiation.     

Phase equilibria in the pseudo-binary In2O3–SnO2 system

The pseudo-binary In₂O₃–SnO₂ phase diagram has been determined in the range of 1000–1650 °C using electron probe microanalysis (EPMA) and x-ray diffraction (XRD) analysis of solid-state sintered samples. The solubility of SnO₂ in In₂O₃ was found to range from 1.3 mol% at 1000 °C to a maximum of 13.1 mol% at 1650 °C, indicating that commercial SnO₂-doped In₂O₃ thin films are thermodynamically metastable. In₂O₃ was found to have negligible solubility in SnO₂ throughout the temperatures examined. In this study two intermediate compounds, In₄Sn₃O₁₂ and In₂SnO_5, were found. Each phase was found to be stable only at high temperatures, decomposing eutectoidally at 1325 and 1575 °C, respectively. This is believed to be the first report of the high temperature phase In₂SnO₅, which is attractive for future research as a transparent conducting oxide.     

Optical characterization of In2S3–SiO2 nanocomposite thin films synthesized by sol–gel technique

In₂S₃–SiO₂ nanocomposite films (with molar ratios of In₂S₃:SiO₂ = 15:85, 10:90 and 5:95) were prepared on quartz substrates by sol–gel method. Highly confined nanoparticles of In₂S₃ (radius ∼ 1.8–7 nm) were obtained in SiO₂ matrix, indicating SiO₂ to be a good capping agent for the nanoparticles. The films were annealed in air at different temperatures (473–623 K) and characterized by optical, microstructural and photoluminescence measurements. XRD studies showed that annealing in air upto 623 K leads to the formation of oxide free In₂S₃ nanoparticles. The broad Photoluminescence peak observed at ∼353 nm showed a marked blue shift associated with a decrease in intensity with increasing concentration of In₂S₃ in the matrix.     

Hybrid MOF Template-Directed Construction of Hollow-Structured In2O3@ZrO2 Heterostructure for Enhancing Hydrogenation of CO2 to Methanol

Direct hydrogenation of CO₂ to methanol using green hydrogen has emerged as a promising method for carbon neutrality, but qualifying catalysts represent a grand challenge. In₂O₃/ZrO₂ catalyst has been extensively applied in methanol synthesis due to its superior activity; however, the electronic effect by strong oxides-support interactions between In₂O₃ and ZrO₂ at the In₂O₃/ZrO₂ interface is poorly understood. In this work, abundant In₂O₃/ZrO₂ heterointerfaces are engineered in a hollow-structured In₂O₃@ZrO₂ heterostructure through a facile pyrolysis of a hybrid metal–organic framework precursor MIL-68@UiO-66. Owing to well-defined In₂O₃/ZrO₂ heterointerfaces, the resultant In₂O₃@ZrO₂ exhibits superior activity and stability toward CO₂ hydrogenation to methanol, which can afford a high methanol selectivity of 84.6% at a conversion of 10.4% at 290 °C, and 3.0 MPa with a methanol space-time yield of up to 0.29 g_MeOH g_cat⁻¹ h⁻¹. Extensive characterization demonstrates that there is a strong correlation between the strong electronic In₂O₃–ZrO₂ interaction and catalytic selectivity. At In₂O₃/ZrO₂ heterointerfaces, the electron tends to transfer from ZrO₂ to In₂O₃ surface, which facilitates H₂ dissociation and the hydrogenation of formate (HCOO*) and methoxy (CH₃O*) species to methanol. This study provides an insight into the In₂O₃-based catalysts and offers appealing opportunities for developing heterostructured CO₂ hydrogenation catalysts with excellent activity.     

Synthesis of BaTi2O5 nanobelts

BaTi₂O₅ nanobelts with 60–100 nm in thickness, 200–300 nm in width, and several micrometers in length have been successfully synthesized through a two-step hydrothermal reaction. Sodium titanate nanobelts are synthesized via the reaction of titania nanoparticles and NaOH aqueous solution at 180 °C for 24 h. After the reaction, resulting sodium titanate nanobelts are ion-exchanged with barium ions and then treated at 180 °C for 60 h under alkaline condition, BaTi₂O₅ nanobelts are formed. The morphologies and crystal structures of sodium titanate and BaTi₂O₅ nanobelts are characterized by field-emission scanning electron microscope (FE-SEM), transmission electron microscope (TEM) and X-ray powder diffractometer (XRD), respectively.     

Synthesis and optical properties of cubic In2S3 hollow nanospheres

The cubic β-In₂S₃ hollow nanospheres was fabricated via two-step solvothermal approaches using InCl₃·4H₂O, CS₂, and thioacetamide (C₂H₅NS) as the starting materials. The as-prepared cubic β-In₂S₃ possessed hollow nanosphere structures, whose outward diameters and shells are −75 and 20 nm, respectively. The samples were characterized by XRD, FESEM, TEM, SAED, and HRTEM. The optical properties of the cubic β-In₂S₃ hollow nanospheres were also investigated. UV–vis (280 nm) and PL (367 nm) spectra indicate that there exists obvious blue shift compared with the In₂S₃ bulk materials.     

Molten salt synthesis of SnS2 microplate particles

A molten salt method to synthesize SnS₂ nanoplates, in a melt of tin dichloride and thiourea in air at 250–280 °C for 0–5 h, coupled with a subsequent washing treatment using distilled water, is demonstrated. The X-ray diffraction, Raman spectra, and field emission scanning electron microscope images disclosed that all the obtained products were phase pure hexagonal SnS₂ nanoplates, of 20–70 nm thickness.     

Discrepancy of room temperature ferromagnetism in Mo-doped In 2 O 3

Molybdenum-doped indium oxide nanopowders were synthesized via mechanical alloying with subsequent annealing at a relatively low temperature of 600  $^{\circ}$ C. The morphologies and crystal structures of the synthesized nanopowders were examined by using scanning electron microscopy (SEM) and X-ray diffraction patterns. X-ray diffraction pattern of the milled mixture shows the presence of both In₂O₃ phase and Mo element. The presence of broad peaks in the pattern confirms that the synthesized powders are nanosized. The X-ray diffraction of annealed samples at 600  $^{\circ}$ C shows the absence of Mo peaks revealing that the Mo was incorporated into the crystal lattices of In₂O₃. Interestingly, it was observed that the diffraction peaks were still broad in the annealed samples indicating the single phase at the nanoscale. From the XRD pattern, the calculated crystallite sizes were in the range of 12–18 nm. Magnetic properties of the synthesized Mo-doped In₂O₃ nanopowders were examined and it was found that the obtained nanopowders possess diamagnetic properties.     

Cordierite as catalyst support for nanocrystalline CuO/Fe2O3 system

CuO, Fe₂O₃ and CuO–Fe₂O₃ samples supported on cordierite (commercial grade) were prepared by wet impregnation method using finely powdered support material, copper and/or iron nitrates. The extent of loading was varied between 5 and 20 wt.% CuO, Fe₂O₃ or CuO–Fe₂O₃. The physicochemical, surface and catalytic properties of the various solids calcined at 350–700 °C were investigated using XRD, EDX, nitrogen adsorption at 77 K and CO-oxidation by O₂ at 220–280 °C.The results obtained revealed that the employed cordierite preheated at 350–700 °C was well-crystallized magnesium aluminum silicate (Mg₂Al₄Si₅O₁₈). Loading of 20 wt.% CuO or Fe₂O₃ on the cordierite surface calcined at 350 °C led to a partial dissolution of the added oxides in the support lattice forming solid solutions. The other portions remained as separate nanocrystalline CuO or Fe₂O₃ phases. The dissolved portions of the transition metal oxide increased upon increasing the calcination temperature from 350 to 500 °C. Loading of 20 wt.% CuO–Fe₂O₃ on the cordierite surface followed by calcination at 350 °C resulted in a solid–solid interaction between some of CuO and Fe₂O₃ yielding iron cuprate Fe₂CuO₄, which decomposed at ≥500 °C yielding copper and iron oxides. The portion of Fe₂O₃ dissolved in the cordierite lattice at 500 °C is twice that of CuO.The S_BET of cordierite increased several times by treating with small amounts of Fe₂O₃ or CuO. The increase was more pronounced by treating with Fe₂O₃. The catalytic activity of the cordierite increased progressively by increasing the amount of oxide(s) added. The mixed oxides system supported on cordierite and calcined at 350–700 °C showed catalytic activities much bigger than those measured for the individual supported systems. The synergistic effect manifested in case of solids calcined at 350 °C was attributed to the formation of surface iron cuprate. The significant increase in surface concentration of copper species on top surface layers of the solids treated with mixtures of copper and ferric oxides could be responsible for the synergistic effect for the mixed oxide catalysts calcined at 500 or 700 °C.     

Microstructure and optical properties of Al2O3/ZrO2 nano multilayer thin films prepared by pulsed laser deposition

The aluminium oxide/zirconium oxide (Al₂O₃/ZrO₂) nanolaminate thin films (5/20 nm with 4 bilayers, 5/15 nm with 5 bilayers and 5/10 nm with 7 bilayers) were deposited on Si (100) and quartz substrates at an optimized oxygen partial pressure of 3 × 10⁻² mbar at room temperature using pulsed laser deposition. The multilayer films were characterized using X-ray diffraction, X-ray reflectivity, Atomic force microscopy and UV–Visible spectroscopy. The X-ray diffraction studies showed amorphous nature for 5/20 nm film, whereas 5/15 nm and 5/10 nm multilayers showed only tetragonal zirconia at room temperature. X-ray reflectivity studies showed the Kiessig fringes and Bragg peaks, indicating the well defined formation of individual layers and bilayer periodicity in the multilayer films. The AFM studies showed the RMS roughness values of 0.7 nm, 0.9 nm and 1.1 nm for 5/10 nm, 5/15 nm and 5/20 nm multilayers respectively. The optical performance of the combined Al₂O₃/ZrO₂ nanolaminates showed that the refractive indices of the films increased from 1.75 to 1.99 with the decrease of ZrO₂ layer thickness from 20 to 10 nm.     

Synthesis and characterization of ultrafine Co–30 wt.%NbC composite powder with a core/rim structure

Ultrafine Co–30 wt.%NbC composite powder with a core/rim structure was synthesized via a direct reduction and carbonization process at 950 °C for 2 h under a vacuum condition. Results show that the particle size of the composite powder is about 150–200 nm. The size of a NbC core is about 110–140 nm and the thickness of its rim is 30 nm approximately. Comparative experiments and thermodynamic calculations indicate that the carbothermal process was greatly improved by the participation of Co₃O₄ in the raw material.     

Preparation of Sb<Subscript>2</Subscript>S<Subscript>3</Subscript> film on functional organic self-assembled monolayers by chemical bath deposition

In this work, self-assembled monolayers (SAMs) of octadecyltrichlorosilane (OTS) were applied to induce the nucleation and growth of the antimony sulfide (Sb₂S₃) films on the functional ITO glass substrate at low temperature. The structure, morphology, and optical properties of the Sb₂S₃ films were investigated by X-ray diffraction, scanning electron microscopy, X-ray energy dispersive spectroscopy, and UV–vis spectroscopy. After thermal treatment at 200 °C for 1 h in air, the orthorhombic Sb₂S₃ was formed as a predominant phase in the deposited thin films. When the deposited films were thermally treated at 400 °C for 1 h in air, the orthorhombic Sb₂S₃ was decomposed and a cubic Sb₂O₃ was formed. The optical band energies of the as-deposited and thermally treated Sb₂S₃ films at 200 °C for 1 h in air and nitrogen were found to be 2.05 eV, 1.77, and 1.76 eV, respectively. As chemical templates, the OTS-functionalized SAMs played an important role in controlling the nucleation and growth of Sb₂S₃ films at low temperature. The results obtained from different preparation parameters applied in the present work will allow controlling the growth of the Sb₂S₃ films with uniform surface.