Characterization and antibacterial capabilities of nanocrystalline CdS thin films prepared by chemical bath deposition

Antibacterial capabilities of nanocrystalline cadmium sulfide (CdS) thin films have been developed against Gram-positive and Gram-negative bacteria in dark and sunlight at 60 °C. For this purpose, a strain of Gram-positive Staphylococcus aureus, and two strains of Gram-negative bacteria (Pseudomonas aeruginosa, and Escherichia coli) were used. The nanocrystalline CdS thin films have been prepared using a chemical bath deposition (CBD) method at different thicknesses (50, 80 and 100 nm). The different deposition parameters including the speed of rotation of substrate, temperature of chemical bath, pH of solution and time of the deposition were optimized. The Polyvinylpyrrollidone (PVP) was successfully used as capping agent in order to stop the agglomeration in the CdS thin films. It was found that, CdS thin films have remarkable antibacterial activity in dark and sunlight and it could be applied as antimicrobial agent in medical field. In order to confirm the crystalline structure of CdS thin films, the polycrystalline nature of the deposited CdS thin films with hexagonal structure was obtained. Furthermore, the structural parameters including lattice parameters, cell volume, the space group, average grain size, dislocation density and the strain have been calculated. The topography and surface roughness of the CdS thin films have been studied before and after the bacteriostatic effect using Scanning Electron Microscopy (SEM). Furthermore, the compositions of nanocrystalline CdS thin films have been evaluated using Energy Dispersive X-ray emission (EDX) and a Transmission Electron Microscope (TEM). Based on the optical measurements in the range of 300–2500 nm, the band gap energy of the prepared CdS thin films was found to be 2.4 eV.     

Growth mechanisms and their effects on the opto-electrical properties of CdS thin films prepared by chemical bath deposition

Chemically deposited CdS exhibits high sensitivity in the opto-electrical performance to the growth mechanisms. Hence it is of a great interest to study the effects of growth mechanisms on the opto-electrical performance in such films. Studies were carried out by the means of spectroscopic ellipsometry, and coupled with structural, optical, and electrical characterization. A range of bath temperatures (55 °C–95  °C) were used as the means to alter the growth mechanisms. Ion-by-ion process dominated deposition at lower bath temperatures throughout the length of the deposition. This mechanism produced films composed of single phase cubic crystals with corresponding opto-electrical properties inherent to such structures. Complex formations at higher bath temperatures supplement the sole ion-by-ion mechanisms with the cluster-by-cluster mechanism. This results in a mixed cubic/hexagonal structure, and deviation from stoichiometry. As a result, carrier concentrations and mobility increased nearly eight and four fold respectively. Resistivity decreased more than four times from 33.2 to 7.5 Ω cm. A noticeable decrease of, ~0.2 was observed in the refractive index and an increase of ~0.07 eV in the band gap is also reported. Nuclear magnetic resonance analysis confirms deviation from stoichiometry in the cluster-by-cluster mechanisms, resulting in interstitially trapped Cd⁺² and S⁻² ions. The trapped ions act as donors in the film enhancing its electrical performance.     

Effect of deposition temperature on structural,optical properties and configuration of CdSe nanocrystalline thin films deposited by chemical bath deposition

CdSe nanoparticle thin films were deposited on glass substrates by the chemical bath deposition (CBD) method at low deposition temperature ranging from room temperature up to 50 °C while the pH of the bath was kept constant at 12.1. The structural and morphological variation were investigated by X-ray diffraction (XRD) and scanning electron microscopy (SEM) technique. The energy band gap and optical properties were characterized by the absorbance spectra. Rutherford backscattering spectroscopy (RBS) analysis reveals the excess of Cd rather than Se in depth profile along the thin film thickness. The prepared CdSe nanoparticles have cubic structure and by increasing the temperature the deposited films become continues, homogeneous and tightly adherent. The results also revealed that by increasing the deposition temperature from room temperature up to 50 °C, the band gap decreases from 3.52 eV up to 1.84 eV.     

Synthesis and characterization of CdSe nanocrystalline thin films deposited by chemical bath deposition

Cadmium selenide (CdSe) nanocrystalline thin films were prepared by chemical bath deposition (CBD) using ammonia and triethanolamine (TEA) as complexing agents, cadmium chloride and sodium selenosulphate as the sources of Cd²⁺ and Se^2? ions, respectively. The structural and optical properties of CdSe nanocrystalline thin films were investigated as a function of the sodium selenosulphate concentrations or ammonia concentrations in precursors using scanning electron microscopy (SEM), energy dispersive spectrometer (EDS), X-ray diffraction (XRD) measurements, transmission electron microscopy (TEM) and UV–visible spectrophotometer measurements. The results reveal that the CdSe thin films are in the pure cubic phase, which composed of a large number of uniform spherical particles. Each spherical particle contains many nanocrystals 3–10 nm in crystallite size. An increase in both the average diameter of the spherical particles and the crystallite size of the nanocrystals occurs with an increase in ammonia concentrations. The Se/Cd atom ratios of CdSe thin films firstly increase and then decrease with an increase in ammonia concentration or sodium selenosulphate concentration. The optical band gap of CdSe thin films decrease with an increase in ammonia concentrations. The kinetics and reaction mechanism of the CdSe nanocrystalline thin films during deposition are discussed.     

Resistive switching behavior of Sb2S3 thin film prepared by chemical bath deposition

The chalcogenides are the excellent memristor materials. Here we report the resistive switching properties of an amorphous Sb₂S₃ thin film. Sb₂S₃ films were deposited on FTO glass using a low-temperature (10 °C) chemical bath deposition technique. SEM and XRD results indicate that the as-grown Sb₂S₃ film is dense and amorphous with uniform thickness and smooth surface. The Ag/Sb₂S₃/FTO memristor shows typical bipolar switching behavior with low operating voltage, high resistance ratio, long retention time, and good endurance. The electrical tests demonstrate that the switching behavior of the amorphous Sb₂S₃ film is based on electrochemical metallization mechanisms.     

Effect of temperature on structural and optical properties of ZnS thin films by chemical bath deposition without stirring the reaction bath

ZnS thin films were deposited at different temperatures on glass substrates by chemical bath deposition method without stirring the deposition bath. With deposition temperature increasing from 50 °C to 90 °C, pH decreases rapidly, homogeneous precipitation of ZnS, instead of Zn(OH)₂ easily forms in the bath. It means that higher temperature is favorable for the formation of relatively high stoichiometric film, due to the lower concentration of OH⁻. The thickness of the films deposited at 90 °C is much higher than that of the films deposited at 50 °C and 70 °C. Combining the film thickness with the change of pH, the growth of film, especially deposited at 90 °C mainly comes from the fluctuation region of pH. At the same time, with the increase of deposition temperature, the obtained films are transparent, homogeneous, reflecting, compact, and tightly adherent. The ZnS films deposited for 1.5 h, 2 h and 2.5 h at 70 °C and 90 °C have the cubic structure only after single deposition. The average transmission of all films, especially the thicker films deposited at 90 °C, is greater than 90% for wavelength values in the visible region. Comparing with the condition of stirring, the structural and optical properties of films are improved significantly. The direct band gaps range from 3.93 to 4.06 eV.     

CdS纳米薄膜的水浴法制备与表征

CdS是一种直接能隙半导体，其带隙约为2．42eV，是一种良好的太阳能电池窗口层材料和过渡层材料。化学水浴法沉积CdS薄膜具有工艺简单，成本低廉，成膜均匀、致密以及可大面积生产等优点。本文通过对化学水浴法沉积CdS薄膜的研究，阐述了CdS膜的生成和生长过程及其机理，并不断优化此方法中的各种工艺参数，得到了适合做铜铟镓硒薄膜太阳能电池过渡层的CdS薄膜，并对该薄膜的形貌、结构和性能进行了分析。     

SnS thin films deposited by chemical bath deposition, dip coating and SILAR techniques

The SnS thin films were synthesized by chemical bath deposition (CBD), dip coating and successive ionic layer adsorption and reaction (SILAR) techniques. In them, the CBD thin films were deposited at two temperatures: ambient and 70 ℃. The energy dispersive analysis of X-rays (EDAX), X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy (SEM) and optical spectroscopy techniques were used to characterize the thin films. The electrical transport properties studies on the as-deposited thin films were done by measuring the I-V characteristics, DC electrical resistivity variation with temperature and the room temperature Hall effect. The obtained results are deliberated in this paper.     

不同方法及衬底类型对CdS多晶薄膜性能的影响

采用化学水浴法和磁控溅射法分别在AZO、FTO、ITO透明导电玻璃衬底上制备了CdS薄膜,利用扫描电镜、XRD以及透射光谱等测试手段,研究了两种制备方法对不同衬底生长CdS薄膜形貌、结构和光学性能的影响.研究结果表明,不同方法制备的CdS薄膜表面形貌均依赖于衬底的类型,水浴法制备的CdS薄膜晶粒度较大,表面相对粗糙.不同方法制备的CdS薄膜均为立方相和六角相的混相结构,溅射法制备的多晶薄膜衍射峰清晰、尖锐,结晶性较好.水浴法制备的CdS薄膜透过率整体低于溅射法,但在短波处优势明显.     

Preparation and characterization of ZnS thin films prepared by chemical bath deposition

Zinc sulfide thin films were prepared by chemical bath deposition technique using zinc sulfate (ZnSO₄·7H₂O) and thiourea [SC(NH₂)₂] as sources of Zn²⁺ and S^2– ions, and ammonia (NH₃) and hydrazine hydrate (N₂H₄) as complexing agents. The structural, stoichiometric proportion, morphology and optical properties of the ZnS thin films were investigated as a function of thiourea and ammonia concentrations using X-ray diffraction (XRD), energy-dispersive spectroscopy (EDS), scanning electron microscopy (SEM) and UV-visible spectrophotometry measurements. The deposition mechanism is discussed. The results reveal that the ZnS films exhibit poor crystallinity. The ammonia concentration had an obvious effect on the surface morphology, optical properties and deposition mechanism. The S/Zn atomic ratio and optical bandgap of the ZnS thin films first increased and then decreased with increasing ammonia or thiourea concentration.     

Optical properties of chemical bath deposited CdS thin films

CdS thin films have been prepared by chemical bath deposition. As-deposited films are cubic and show a sulfur deficiency. From the transmittance and reflectance data analysis direct band gaps (E_g) ranging from 2.180 to 2.448 eV have been obtained. Air and vacuum annealed samples show a decrease in the band gap. The refractive index (n) lies in the range 1.61–2.34. A dependence of band gap on composition has been observed and the possible reasons are discussed.     

Comparative studies on the structural,morphological, optical,and electrical properties of nanocrystalline PbS thin films grown by chemical bath deposition using two different bath compositions

High-quality lead sulfide (PbS) thin films were synthesized by chemical bath deposition from two baths with different compositions. One of them (bath-І) contained an aqueous solution of lead acetate, thiourea, sodium hydroxide, and the second (bath-ІІ) had additional triethanolamine. The introduction of triethanolamine reduced the grain size and increased the optical band gap of the PbS nanoparticles. The structure, morphology, and optical properties of the obtained films were investigated and compared with respect to the deposition time. X-ray diffraction data were used to obtain the crystallite size, lattice constant, and strain of the films. Atomic force microscopy results show that the roughness and rms-surface slope of the samples obtained from bath-I (PbS-I) were higher than those of bath-II (PbS-II) samples. PbS thin films with high reflectance (~61%) in the near-infrared region, which is important in our solar system, were obtained. The band gap, extinction coefficient, and refractive index of the samples were calculated. Furthermore, Raman analysis was performed and electrical properties of the samples were studied.     

CIGS薄膜太阳能电池缓冲层CdS薄膜的制备研究

目前CdS材料的制备方法有很多种,但是最常用的是化学水浴法。本文研究了浓度、反应溶液pH值、温度、沉积时间对CdS缓冲层薄膜的影响,对CIGS薄膜太阳能电池缓冲层CdS薄膜的制备方法进行了论述。     

化学水浴法制备CdS薄膜退火工艺的研究

基于化学水浴沉积法以硫脲为硫源,醋酸镉为镉源,氨水作为缓冲剂,制备太阳能电池用半导体薄膜硫化镉(CdS),研究不同的退火温度和是否涂敷CdCl2溶液对CdS薄膜的影响。采用X线衍射仪、电子扫描电镜和紫外/可见光分光光度计研究了不同退火工艺对硫化镉薄膜的结构、形貌及光学特性的影响。实验表明,悬涂CdCl2溶液退火处理可明显改善CdS薄膜的结晶及其光学性质,最佳退火温度为400℃,退火时间为60min。     

Low-cost TiO2/Sb2(S,Se)3 heterojunction thin film solar cell fabricated by sol-gel and chemical bath deposition

Low cost TiO₂/ Sb₂(S, Se)₃ heterojunction thin film solar cell are prepared successfully by using sol-gel and chemical bath deposition. At first, TiO₂ thin film is prepared on the ITO-coated glass substrate by a simple sol-gel and dip-coating method. Subsequently, Sb₂(S, Se)₃ film is fabricated on TiO₂ by selenizing the Sb₂S₃ film prepared by chemical bath deposition (CBD). The heat-treated process of TiO₂ and Sb₂(S, Se)₃ films has been discussed, respectively. After being heat-treated at 550 °C for TiO₂ and 290 °C for Sb₂(S, Se)₃ films, the photovoltaic devices are completed with the conductive graphite as electrode. The J-V characteristics of TiO₂/ Sb₂(S, Se)₃ solar cell are measured and the open circuit voltage (V_oc) of this cell is about 350 mV.     

Surfactant assisted chemical bath deposition based synthesis of 1-D nanostructured CuO thin films from alkaline baths

Nanostructured CuO thin films were prepared by a simple chemical bath deposition method in the absence and presence of different surfactants. The obtained structures were characterised on the basis of x-ray diffraction (XRD), scanning electron microscopy (SEM), Raman spectroscopy and UV–Vis spectral absorption. XRD and Raman studies pointed to the formation of a pure phase of monoclinic CuO. SEM studies revealed 1-D nanostructures of different orientations and aspect ratios. The presence of surfactants produced more uniform and oriented nanostructures. The samples were absorbing in the UV–Vis region demonstrating their potential application in photothermal systems. All the samples showed photocatalytic activity against methylene blue with different degradation efficiencies.     

Influence of ammonia concentration on the microstructure,electrical and raman properties of low temperature chemical bath deposited ZnO nanorods

Nanostructured zinc oxide synthesized using an easy and low temperature chemical bath deposition method are among the most promising low cost semiconducting nanostructures investigated for a variety of applications. We successfully report the effects of ammonia solution in the growth of ZnO nanorods at a temperature of 60 °C. Successive addition of ammonia altered the degree of supersaturation of the growth solution, causing a significant deviation in the morphology and crystal orientation of ZnO nanorods. Field emission scanning Electron Microscopy images revealed changes in surface morphology of ZnO nanorods with respect to addition of specific amounts of ammonia. X-ray diffraction analysis revealed wurtzite crystal structure of ZnO which was further supported by X-ray photoelectron studies, optical absorbance and Raman spectra that also revealed the existence of wurtzite ZnO. The current-voltage measurement showed the electrical properties of the synthesized ZnO nanorods. The vertically grown nanorods with flat tops, effect more rectifying Schottky contacts to be realized on comparison to needle like structures.     

Modification of the dark and photoconductivity and the optical transmittance of solution-grown CdS thin films

Very interesting behaviour is shown by chemically deposited CdS thin films for optoelectronic applications after air and vacuum (10^?5 Torr) annealing. Vacuum annealing of samples at about 100°C caused the dark conductivity to improve by five orders of magnitude. The dark and photoconductivity of air-annealed (at around 200°C) samples increased by seven and two orders of magnitude respectively. Air-annealed (at 350°C for about 2 min) samples exhibited a very quick photoresponse (<2 s for two decades of photocurrent decay) with σ_p/σ_d ≈ 10⁵ for a bias of 10 V, which may be exploited for photodetector applications. Air or vacuum annealing of samples for a minimum of 10–15 min caused the optical transmittance above the band edge to increase by 10%–15% and annealing the sample at 200°C caused the absorption edge to shift towards the longer-wavelength region compared with the as-prepared and 100 and 350°C annealed films.     

Effect of four different zinc salts and annealing treatment on growth,structural, mechanical and optical properties of nanocrystalline ZnS thin films by chemical bath deposition

ZnS thin films were deposited from four different zinc salts on glass substrates by chemical bath deposition method. Different anions of zinc salts affect the deposition mechanism and growth rate, which influence the properties of the films significantly. The ZnS thin film deposited from ZnSO₄ is smoother, thicker, more homogeneous and compact, nearly stoichiometric, comparing with the films deposited from Zn(CH₃COO)₂ and Zn(NO₃)₂, and ZnCl₂. The scratch test of bonding force between ZnS film and substrate shows that the ZnS film deposited from ZnSO₄ has the most excellent adhesion with the substrate. The presence of SO₄²⁻ promotes heterogeneous ZnS thin film growth via ions by ions deposition, and the films deposited from Zn(CH₃COO)₂ and Zn(NO₃)₂ are formed via clusters by clusters deposition. XRD and HRTEM results show that cubic ZnS films are obtained after single deposition, and the grain size of ZnS thin film deposited from ZnSO₄ for 2.5 h is 10 nm. The average transmission of all films is greater than 85% in the wavelength ranging from 600 to 1100 nm, and the transmission of films deposited from ZnSO₄ or Zn(NO₃)₂ for 1.5, 2 and 2.5 h is greater than 85% in the wavelength varying from 340 to 600 nm, which can enhance the blue response. The band gaps of all ZnS thin films are in the range of 3.88–3.99 eV. After annealing treatment, the mechanical and optical properties of the ZnS thin film deposited from ZnSO₄ are improved significantly.     

水浴沉积法制备硫化镉薄膜的初步研究

采用化学水浴沉积法制备了半导体薄膜硫化镉（CdS）太阳能电池材料,对影响成膜的因素以及薄膜的结构和光学性能进行了初步测试研究。结果表明,反应溶液的pH值以及薄膜的退火温度是影响成膜的重要因素。实验中pH值范围控制在10．5—10．8之间,最佳退火温度为400℃。另外退火时滴加CdCl2溶液并将其涂抹于薄膜表面,可以使薄膜在可见光范围的透过率得到进一步的提高。