xS Films Research Articles

Enhancement of the Seebeck Coefficient by Energy Filtering in Mixed-Phase Cu2−xS Films at Room Temperature

Enhancement of the Seebeck Coefficient by Energy Filtering in Mixed-Phase Cu2−xS Films at Room Temperature

Largely Enhanced Thermoelectric Power Factor of Flexible Cu2-xS Film by Doping Mn.

Copper-sulfide-based materials have attracted noteworthy attention as thermoelectric materials due to rich elemental reserves, non-toxicity, low thermal conductivity, and adjustable electrical properties. However, research on the flexible thermoelectrics of copper sulfide has not yet been reported. In this work, we developed a facile method to prepare flexible Mn-doped Cu2-xS films on nylon membranes. First, nano to submicron powders with nominal compositions of Cu2-xMnyS (y = 0, 0.01, 0.03, 0.05, 0.07) were synthesized by a hydrothermal method. Then, the powders were vacuum-filtrated on nylon membranes and finally hot-pressed. Phase composition and microstructure analysis revealed that the films contained both Cu2S and Cu1.96S, and the size of the grains was ~20-300 nm. By Mn doping, there was an increase in carrier concentration and mobility, and ultimately, the electrical properties of Cu2-xS were improved. Eventually, the Cu2-xMn0.05S film showed a maximum power factor of 113.3 μW m-1 K-2 and good flexibility at room temperature. Moreover, an assembled four-leg flexible thermoelectric generator produced a maximum power of 249.48 nW (corresponding power density ~1.23 W m-2) at a temperature difference of 30.1 K, and had good potential for powering low-power-consumption wearable electronics.

Chemical vapor reaction synthesis and photoelectronic properties of CuS and Cu3SbS4 thin films

Chemical vapor reaction is a simple and efficient experimental means of preparing metal sulphide films. Through systematically studying the effect of vulcanisation temperature on the growth of copper sulfide (CuS) thin film. The copper antimony sulfide (Cu3SbS4) thin film was obtained by further vulcanized Sb/Cu mental film. The structure and optical properties of the as-prepared films were characterized by x-ray diffraction, Raman and photoluminescence spectra. The hexagonal structure of CuS film was confirmed and Cu3SbS4 grew preferentially along the (112) crystal plane. The surface grains of CuS and Cu3SbS4 films were finally condensed into spheres. The content of S and the resistance of the films increase with the increase in temperature, but the bandgap of the films will be decreased. The bandgap of Cu2−xS films prepared at 195 °C−350 °C is in the range of 2.2–2.5 eV and that of Cu3SbS4 thin films prepared at 350 °C is 1.77 eV, and has good absorption in the visible light range. In addition, The Hall effect measurement indicated CuS and Cu3SbS4 films have p-type semiconducting behavior. The carrier concentration and mobility are 2.45 × 1021 cm−3 and 1.28 cm2 Vs−1 for CuS, and 4.30 × 1017 cm−3 and 185.93 cm2 Vs−1 for Cu3SbS4, respectively. The I-T tests show that the CuS and Cu3SbS4 thin films have photoconductive properties.

Variations in the characteristics of CdxZn1−xS films deposited with little Cd-containing solutions

Variations in the characteristics of CdxZn1−xS films deposited with little Cd-containing solutions

Corrigendum to Morphological and structural features of the CdxPb1−xS films obtained by CBD from ethylenediamine-citrate bath

The original article, “Kutyavina AD, Maskaeva LN, Voronin VI, Anokhina IA, Markov VF. Morphological and structural features of the CdxPb1−xS films obtained by CBD from ethylenediamine-citrate bath. Chimica Techno Acta. 2021;8(2):20218210”, is available at: https://doi.org/10.15826/chimtech.2021.8.2.10

Morphological and structural features of the CdxPb1−xS films obtained by CBD from ethylenediamine-citrate bath

The calculating of ionic equilibria in the system «Pb(CH3COO)2 - CdCl2 - Na3C6H5O7 - ‎(NH3)2(CH2)2 - N2H4CS» allowed us to find conditions and concentration regions of PbS and CdS co-deposition. The determined conditions provided the CBD obtaining of CdxPb1−xS (0 ≤ x ≤ 0.033) substitutional solid solutions films with a cubic structure B1 (space group Fm ) with the grains preferred orientation (200). We established the evolution of the surface morphology of the synthesized films from cubic crystallites to hierarchical structure of globular aggregates by scanning electron microscopy. A quantitative analysis of diffraction patterns showed a decrease of microstrains in CdxPb1−xS films by a about factor of 3 with an increase of the cadmium chloride concentration in the reaction mixture from 0.005 to 0.14 mol/l. The excess of the cadmium content, established by EDX analysis, in the studied films as compared to its content in the solid solution is associated with the additional formation of the amorphous CdS phase up to 72 mol %.A Corrigendum is available for this article at https://doi.org/10.15826/chimtech.2021.8.2.12.

Влияние структурно-морфологических характеристик на сенсорные свойства пленок Cd-=SUB=-x-=/SUB=-Pb-=SUB=-1-x-=/SUB=-S

Polycrystalline films of CdxPb1−x S (0.021 ≤ x ≤ 0.090) supersaturated substitutional solid solutions with a cubic structure B1 (Fm3¯m space group) have been obtained with varying cadmium acetate salt Cd(CH3COO)2 in the reaction mixture within 0.01−0.1 mol/l on the sitall substrates. Their thickness changed from ∼ 0.4 to ∼ 1.0 microns. A correlation has been established between the structural-morphological and functional properties of CdxPb1−x S thin-film layers. The extreme character of the voltage sensitivity dependence on the cadmium salt concentration in the reaction bath is associated with the nonmonotonic introduction of cadmium into the PbS crystal lattice. It is shown that the maximum photocurrent is possessed by CdxPb1−x S thin-film layers formed from crystallites with pronounced faceting. We have found the surface sensitivity of the CdxPb1−xS films to the presence of ∼ 0.02 mg/m3 NO2 in the air, which is significantly lower than the maximum allowable concentration.

Chemical bath deposited CdxPb1−xS solid solution films: composition, structure, and optical properties

Films of cubic substitutional CdxPb1−xS solid solutions have been synthesized by the chemical bath deposition with varying cadmium acetate salt Cd(CH3COO)2 in the reaction mixture within 0.01–0.08 mol/l on quartz substrates. The crystal structure, chemical composition and morphology were studied by the X-ray diffraction, scanning electron microscopy, elemental analysis, Auger spectroscopy, and Raman spectroscopy, as well as the evolution of the optical and photoelectric properties was determined. The thickness of the deposited films changes from ~ 0.4 to ~ 1.0 μm, and the content of cadmium x in the CdxPb1−xS solid solution varies from 0.036 to 0.090. All the CdxPb1−xS films have B1 crystal structure (NaCl type), but differ in the morphology (the size, form and predominant orientation of the particles forming the films). Forming the substitution solid solution is confirmed by the shift of the Raman lines at 72 and 134 cm−1 toward higher frequencies. The optical band gap determined from the absorption spectra varies from 0.46 to 0.70 eV. The dependences of the photoresponse value (volt-watt sensitivity) and the dark resistance on cadmium acetate concentration in the solution are represented.

Peculiarities of the Composition and Morphology of CdxPb1 – xS Films Formed on Various Substrates

Chemical deposition from aqueous solutions of films of substitutional CdxPb1 – xS solid solutions with a cubic B1 structure on substrates made of monocrystalline silicon, sitall, conductive ITO coating, and a glass slide is carried out. A comparative analysis of films deposited on substrates made of various materials reveals a number of peculiarities associated with their morphology, granulometric, elemental and phase composition. To improve the quantitative assessment of the structural parameters of CdxPb1 – xS films obtained on various substrates, the profiles of diffraction reflections are proposed to be described by three- or two-phase models, taking into account the background of diffuse scattering from an amorphous material or excluding reflections from the crystalline material of the substrate. X-ray diffraction, XPS spectroscopy, and optical studies have shown that the synthesized films contain, in addition to the CdxPb1 – xS phase, impurity wide-gap compounds of Pb(OH)2, PbCO3 ∙ xPb(OH)2, and CdS.

Deposition of CdS-Cu2−xS films from thiourea coordination compounds and investigation of their properties

Heterophase films containing cadmium sulfide and Cu2−xS phase were prepared by pyrolysis of the aerosol solutions of the thiourea coordination compounds. The crystal structure of the synthesized layers, as well as their optical, electrical, photovoltaic, and luminescent properties were studied. The dependence of the properties of CdS-Cu2−xS films on their composition was revealed. A general scheme of the formation of cadmium and copper sulfides on a fused silica substrate is proposed.

Фотоадсорбционный эффект в пленках твердых растворов CdPbS

In this work, we have attempted to detect the photoadsorption effect using various photoactivation sources of semiconductor layers of CdxPb1–xS solid solutions that are sensitive to the presence of nitrogen dioxide in air. For this purpose, CdxPb1–xS films (up to 600 nm thick) were synthesized from the citrate – ammonia reaction system by the chemical bath deposition (CBD) on glass and sitall substrates. Using XRD analysis, we determined the structure and composition of CdxPb1–xS solid solutions. It was found that all films crystallize in the cubic structure B1 of lead sulfide. Taking into account the content of the substituting component in the samples and comparing it with the equilibrium phase diagrams of the PbS-CdS system, we concluded that the obtained solid solutions are strongly supersaturated in nature. The cadmium content in the PbS lattice increases in films deposited on sitall and glass from 3.9 to 5.9 and from 4.3 to 5.4 at.% with an increase in the deposition time from 60 to 120 minutes, respectively. It must be noted that their crystallinity degree increases with increasing deposition time. The size of the particles forming the layers was determined by SEM microscopy. The predominant crystallite diameter is 250-300 nm. The sensory properties of films of CdxPb1–xS solid solutions with respect to the presence of nitrogen dioxide with a concentration of 100 mg/m3 in air were studied using preliminary photoactivation by various sources with a radiation wavelength from 420 to 1000 nm. For the first time, a positive photoadsorption effect was revealed for CBD produced films of CdxPb1–xS solid solutions. The preliminary photoactivation of the films with a blue lamp (760–1000 nm) for 9-13 minutes allows the film to increase the response to NO2 more than doubled. A high relaxation rate of CdxPb1–xS -based sensor elements after contact with nitrogen dioxide was shown to be 4–10 minutes, which allows to reuse it.

Особенности состава и морфологии пленок Cd-=SUB=-x-=/SUB=-Pb-=SUB=-1-x-=/SUB=-S, сформированных на различных подложках

Chemical deposition of the films consisting of CdxPb1−xS substitutional solid solutions with a cubic B1 structure was carried out from aqueous solutions on the substrates made of single-crystal silicon, sitall, conductive ITO coating and glass. Comparative analysis of films deposited on the various substrates has revealed a number of features associated with their morphology, grain size, elemental and phase composition. It was suggested to describe the diffraction reflection profiles using three- or two-phase models, taking into account the diffuse scattering background from an amorphous material or excluding reflections from the crystalline substrate material in order to increase the quantitative assessment of the structural parameters of CdxPb1−xS films obtained on various substrates. X-ray diffraction, XPS and optical studies have shown that the synthesized films contain, in addition to the CdxPb1−xS phase, impurity wide-gap compounds: Pb(OH)2, Pb(OH)(СН3СОО) and CdS.

Determination of Nitrogen Dioxide by Thin-Film Chemical Sensors Based on CdxPb1 –xS

The results of a study of sensors based on thin semiconductor films of CdxPb1 – xS solid solutions intended for the determination of nitrogen dioxide in air are described. For a comparative assessment of the composition, morphology, and functional properties of the films, they were synthesized from reaction mixtures containing various cadmium salts. It was found that the maximum response is provided by layers obtained using cadmium acetate, in which the composition of the solid solution differs in the maximum supersaturation level in CdS. The films were formed of crystallites with average sizes of ~200 nm. When the concentration of nitrogen dioxide in air was 0.05‒200 mg/m3, the relative change in the ohmic resistance of sensors ranged from 8 to 80%. It was shown that the threshold concentration of NO2 in air was about 0.02 mg/m3. The reversible nature of the gas adsorption process opens a possibility for the creation of reusable chemical sensors based on CdxPb1 – xS films, differing in a relatively low threshold concentration of NO2 detection and selective response in the presence of significantly higher concentrations of O2, CO2, and H2.

A comprehensive study on the structural, morphological, compositional and optical properties of ZnxCd1−xS thin films

The absorption loss in cadmium sulfide (CdS) thin films which are widely used as a window layer in a photovoltaic cell limits the efficiency of the device. This issue can be addressed by ZnxCd1−xS thin films due to its tunable band gap nature. Herein, the various composition of ZnxCd1−xS (x=0, 0.15, 0.30, 0.45, 0.70, 0.85, 1) thin films were grown by a vacuum thermal evaporation technique and the characteristics of the films were investigated by varying the composition ‘x’. The x-ray diffraction (XRD) studies displayed that the as-deposited films consist of diffraction peaks from both CdS and ZnS lattice. The formation of ternary ZnxCd1−xS films was verified when the deposited films were subjected to an annealing treatment. The morphology of the films was analyzed using a scanning electron microscope (SEM) and it was observed that the films are uniform, homogeneous and free from any pin-holes and cracks. The presence of Zn, Cd and S elements were quantized using an energy dispersive spectroscopy. Optical studies showed a successful non-linear band gap engineering (2.42–3.49 eV) for the deposited ZnxCd1−xS thin films. All films showed a very high optical transmittance of above 70% in the visible wavelength region.

Combinatorial Tuning of Structural and Optoelectronic Properties in CuxZn1−xS

Summary P-type transparent conductors (TCs) are important enabling materials for optoelectronics and photovoltaics, but their performance still lags behind n-type counterparts. Recently, semiconductor CuxZn1−xS has demonstrated potential as a p-type TC, but it remains unclear how properties vary with composition. Here, we investigate CuxZn1−xS across the entire alloy space (0 ≤ x ≤ 1) using combinatorial sputtering and high-throughput characterization. First, we find a metastable wurtzite alloy at an intermediate composition between cubic endpoint compounds, contrasting with solid solutions or cubic composites (ZnS:CuyS) from the literature. Second, structural transformations correlate with shifts in hole conductivity and absorption; specifically, conductivity increases at the wurtzite phase transformation (x ≈ 0.19). Third, conductivity and optical transparency are optimized within a "TC regime" of 0.10

Thermal Annealing Influence on the Properties of Heterostructure Based on 2 at.%Eu Doped SnO2 and Cu1.8S

Aiming at optoelectronic applications, a heterostructure based on Eu-doped tin oxide (SnO2) and copper sulfide (Cu2−xS) is built. SnO2 thin films doped with 2 at.% Eu were obtained by the sol–gel dip-coating and spin-coating techniques, whereas the Cu2−xS film was obtained by resistive evaporation. Samples were prepared using three distinct thermal annealing temperatures of the SnO2 bottom layer: 150°C, 250°C and 500°C. Transmittance and absorption spectra of the heterostructure shows high transparency in the visible to near infrared range (600–1800 nm), and considering the dominance of SnO2 on light absorption, it was possible to evaluate the sample indirect bandgap around 3.5 eV, independently of the thermal annealing temperature. Cyclic voltammetry and impedance spectroscopy, in conjunction with calculation of the hysteresis index, show that the heterostructure presents a behavior highly capacitive, and the higher annealing temperature leads to higher capacitance at low frequencies, similar to the observed qualitative behavior of supercapacitive devices. Besides, the sample with the SnO2 bottom layer annealed at 500°C yielded a higher current density.

Morphology and Current Transport in a Thin-Film Polycrystalline Au–ZnxCd1–xS–Mo Structure with Wide Photosensitivity Range in the Ultraviolet and Visible Radiation Spectral Region

Studies are carried out on the morphology of the surface and photovoltaic characteristics of a thinfilm Au–ZnxCd1–xS–Mo structural injection photodetector with a wide photosensitivity range in the ultraviolet and visible radiation spectral regions. The composition of ZnxCd1–xS film in the Au–ZnxCd1–xS–Mo structure with a wide photosensitivity spectrum in the ultraviolet and visible spectrum, where x on the surface varies from 0.22 to 0.24, is studied. The mechanism of current transport is investigated, and the main electrophysical parameters of the semiconducting materials are determined. The use of ZnxCd1–xS film with a variable band gap in the thin-film heterojunction solar cells, where they are used as the buffer layer, will provide an opportunity to increase the photosensitivity of the structure in the short-wave region of the radiation spectrum, increase the value of the built-in potential, short-circuit current and value of the open-circuit voltage of the structure.

Observation of photoluminescence from large-scale layer-controlled 2D ß-Cu2S synthesized by the vapor-phase sulfurization of copper thin films

Two-dimensional (2D) copper chalcogenides (Cu2−xX where X = S, Se, Te) have had much attention regarding various applications due to their remarkable optical and electrical properties, abundance, and environmentally friendly natures. This work indicates that highly uniform Cu2−xS (where 0 < x < 1) nanosheets can be obtained by the two-step method of Cu deposition by sputtering with precisely controlled and extremely low growth rate followed by vapor-phase sulfurization. The phase transformations of thin Cu2−xS films upon the Cu seed layer thickness are investigated. A unique thickness-constrained synthesis process using vapor-phase sulfurization is employed here, which evolves from a vertical to lateral growth mechanism based on the optimization of the Cu seed layer thickness. Atomically thin 2D β-Cu2S film was successfully synthesized using the thinnest Cu seed film. We have systematically investigated the phase- and thickness-dependent optical properties of Cu2−xS films at room temperature. Micro-photoluminescence (PL) spectroscopy reveals that the 2D β-Cu2S film possesses a direct band gap with an energy of 1.1 eV while the PL intensities are greatly suppressed in the multilayer Cu2−xS (where 0 ≤ x < 1).

Investigation of composition and current transport mechanism in polycrystalline thin film ultra violet Au–Zn x Cd1–x S–Mo-structure with narrow spectrum of photosensitivity

The composition and photovoltaic characteristics of Au–Zn x Cd1–x S–Mo–thin film structural injection photo detectors sensitive to narrow the ultraviolet region of the electromagnetic spectrum created and investigated. Studies of the morphology and composition of Zn x Cd1–x S films showed that in the Au–Zn x –Cd1–x S–Mo–UV structure, with a narrow photosensitivity spectrum, x = 0.6 ± 0.02. The features of current transport mechanism in the structure and the basic parameters of semiconductor material are defined. Polycrystalline Zn x Cd1–x S is a wide-band-semiconductor material may be used instead of the CdS buffer layer in various types of heterostructural solar cells. This will give an opportunity to increase the photo sensitivity of the structure in the short-wave part of the radiation spectrum, increase the built-in potential and solve the problem of open circuit voltage deficiency in the thin-film solar cells.

Properties of Cd x Zn1–x S:Cu2+ (0.5 ≤ x ≤ 1) Films Deposited by Pyrolysis of Thiourea Coordination Compounds

The results of a study of Cd x Zn1–x S (0.5 ≤ x ≤ 1) films obtained by pyrolysis of an aerosol from solutions of the coordination compounds [Cd(N2H4CS)2Br2] and [Zn(N2H4CS)2Br2], both pure and doped with copper ions at concentrations of 10−6–10−4 at.%, are presented. The crystal structure of the films was studied. The optical forbidden band gap of the pure and doped films varies from 2.5 eV to 3.1 eV. The introduction of copper impurities increases the photoluminescence intensity by almost one order of magnitude.