Effects of molarity on structural,optical, morphological and CO2 gas sensing properties of nanostructured copper oxide films deposited by spray pyrolysis

In this paper, we have exposed the effects of molarity on structural, optical, morphological and gas sensing properties of copper oxide films deposited by pneumatic spray pyrolysis method. The molar concentration was varied from 0.05 to 0.3 M. X-ray diffractograms showed the formation of a single phase CuO for films prepared with 0.05 and 0.1 M concentrations. A secondary phase Cu₂O was obtained for 0.2 and 0.3 M concentrations. Optical measurements showed that 0.05 M concentration provides a film with the best transparency in the visible and near infrared regions. The thickness values were between 2 and 110 µm. Moreover, the contact angle measurements have shown that all the deposited films are hydrophobic with angles between 103° and 121°. The morphological properties were investigated using SEM and AFM. According to SEM and AFM micrographs, 0.05 M is the concentration that leads to porous structure. The gas sensing measurements confirm that this porous surface structure is the most sensitive to different CO₂ concentrations.     

SnO2：TiO2薄膜氨气敏光纤传感器的研究

本文作者利用ＳｎＯ２：ＴｉＯ２气敏光学薄膜设计制成气敏光纤传感器，并用它测定氨蒸汽浓度，传感器的灵敏范围为１５０￣６０００ｐｐｍ，灵敏度为２００ｐｐｍ。     

Effect of Ce doping on microstructural,morphological and optical properties of ZrO2 nanoparticles

Pure and Ce doped ZrO₂ nanostructures have been synthesized by the microwave irradiation method. The prepared nanoparticles were characterized by various analytical techniques like Thermogravimetric and Differential Thermal Analysis (TG–DTA), X-Ray Diffraction (XRD), Fourier Transform Infra-Red Spectroscopy (FTIR), Scanning Electron Microscopy (SEM), Energy Dispersive Spectrum (EDS) and Transmission Electron Microscopy (TEM). The XRD pattern of Ce doped ZrO₂ nanoparticles have been confirms that the tetragonal structure. TEM observations indicated that the average particle size of the pure ZrO₂ some particles spherical shaped and some particles agglomeration in the range of 16–44 nm. Whereas on addition of Ce agglomeration in the range of 32–56 nm. The pure ZrO₂ and Ce doped ZrO₂ nanoparticles were further characterized for their optical properties by UV–vis reflectance spectra (DRS) and Photoluminescence (PL) spectroscopy.     

Investigation of structural,optical and morphological properties of copper doped zinc sulphide nanoparticles

Semiconductor nanoparticles doped with transition metal ions can influence the transition probabilities and electronic structure. The undoped and copper doped zinc sulphide nanoparticles with various concentrations are synthesized by wet chemical co-precipitation method. These nanoparticles are characterized by using X-ray powder diffraction (XRD), Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), Selected Area Electron Diffraction (SAED), UV–visible (UV–vis) absorption spectroscopy, Fourier Transform Infrared (FT-IR) Spectroscopy, conductivity measurement and time-resolved photoluminescence studies. X-ray powder diffraction analysis reveals that the synthesized samples have cubic zinc blende structure. The Scanning Electron Microscope shows the synthesized nanoparticles are agglomerated. The UV–visible spectra reveal the absorption edge is red shifted. The FT-IR spectra show vibrational peaks around 617 cm⁻¹ which indicate the presence of Cu–S stretching modes. The AC conductivity measurement confirms the semiconducting nature and shows a marked increase in conductivity as the doping concentration of copper increases. The photoluminescence shows that the emission at 426 nm may be due to transition from the conduction band to the zinc vacancies. These transition metal ions doped semiconductor nanoparticles have important applications in solid state lighting, imaging, and other photonic devices.     

Effect of yttrium doping on structural and optical properties of zinc sulfide nanoparticles

Present work deals with the effect of Yttrium (Y) doping on the structural and optical properties of Zinc Sulfide (ZnS) nanoparticles synthesized by chemical co-precipitation method. The incorporation of Y in ZnS structure and the resulting elemental composition were confirmed using EDAX analysis. The SEM and HR-TEM images depicted the formation of ZnS agglomerates with narrow size distribution. Using XRD spectra it was analyzed that with increase in concentration of Y atoms, the crystallinity of ZnS lattice structure decreases, a significant deviation in the lattice structure was observed at 15 wt% Y doping. Raman analysis showed a monotonic decrease in vibration frequency of ZnS lattice with the incorporation of bulky Y ions. A decrease in the band gap from 3.97 to 3.75 eV was also observed with increase in Y doping upto 15 wt%. The photoluminescence spectra depicted that Y doping has a strong effect on the emission properties of the ZnS nanoparticles. Initially, it enhances the band edge emission by occupying the Zn vacancies in the lattice structure but at higher doping levels their tendency to move into the interstitial sites suppresses back the band edge emission. The blue emission from S vacancies is also observed to increase with Y doping.     

Effect of terbium doping on structural,optical and gas sensing properties of In2O3 nanoparticles

In this work, the effect of terbium (Tb³⁺) as dopant on the structural, optical, electrical and gas sensing properties of In₂O₃ (indium oxide) nanoparticles has been discussed. In₂O₃ and Tb³⁺-doped In₂O₃ nanoparticles were synthesized by a facile and cost effective co-precipitation method. XRD analysis revealed the formation of bixbyite-type cubic phase for In₂O₃ and Tb³⁺-doped In₂O₃ nanoparticles which was further supported by Raman studies. It was observed that the crystallite size of In₂O₃ nanoparticles decreased, while structural disorder increased with increase in Tb³⁺ concentration. SEM micrographs showed that particles were spherical in shape and EDS corroborated the presence of Tb³⁺ in doped In₂O₃ nanoparticles. A broadening and shifting of Raman peaks with increase in Tb³⁺ content was also observed. For gas sensing characteristics, the nanoparticles were applied as thick film onto the alumina substrate and tested at different operating temperatures for various volatile organic compounds (such as methanol, ethanol, acetone) and ammonia. The results indicated that the sensor based on 5%Tb³⁺-doped In₂O₃ nanoparticles presented much higher sensor response to 50ppm ethanol at 300 °C temperature than the pure In₂O₃ sensor. The enhancement of the response may be attributed to high surface basicity, small size and large lattice distortion of doped In₂O₃ sensor.     

Effects of Sb,Zn doping on structural,electrical and optical properties of SnO2 thin films

Highly transparent, low resistive pure and Sb, Zn doped nanostructured SnO₂ thin films have been successfully prepared on glass substrates at 400° C by spray pyrolysis method. Structural, electrical and optical properties of pure and Sb, Zn doped SnO₂ thin films are studied in detail. Powder X-ray diffraction confirms the phase purity, increase in crystallinity, size of the grains (90–45 nm), polycrystalline nature and tetragonal rutile structure of thin films. The scanning electron microscopy reveals the continuous change in surface morphology of thin films and size of the grains decrease due to Sb, Zn doping in to SnO₂. The optical transmission spectra of SnO₂ films as a function of wavelength confirm that the optical transmission increases with Sb, Zn doping remarkably. The optical band gap of undoped film is found to be 4.27 eV and decreases with Sb, Zn doping to 4.19 eV, 4.07 eV respectively. The results of electrical measurements indicate that the sheet resistance of the deposited films improves with Sb, Zn doping. The Hall measurements confirm that the films are degenerate n-type semiconductors.     

SnO_2-ZnO的乙醇气敏特性研究

为了解决乙醇传感器灵敏度不够高和选择性较差的问题,使用稀土金属氧化物代替贵金属及其化合物作为催化剂和添加剂制成了以SnO2-ZnO为主体的气敏材料,并对其气敏性能进行了研究。结果表明,此方法可有效提高SnO2-ZnO气敏材料对乙醇气体的灵敏度及选择性;利用制成的SnO2-ZnO气敏材料,可以生产出高灵敏度、高选择性的乙醇传感器。     

Effect of processing parameter on structural,optical and electrical properties of photovoltaic chalcogenide nanostructured RF magnetron sputtered thin absorbing films

The aim of this work was to develop high quality of CuIn_1−xGa_xSe₂ thin absorbing films with x (Ga/In+Ga)<0.3 by sputtering without selenization process. CuIn_0.8Ga_0.2Se₂ (CIGS) thin absorbing films were deposited on soda lime glass substrate by RF magnetron sputtering using single quaternary chalcogenide (CIGS) target. The effect of substrate temperature, sputtering power & working pressure on structural, morphological, optical and electrical properties of deposited films were studied. CIGS thin films were characterised by X-ray diffraction (XRD), Field emission scanning electron microscope (FE-SEM), Energy dispersive X-ray spectroscopy (EDAX), Atomic force microscopy (AFM), UV–vis–NIR spectroscopy and four probe methods. It was observed that microstructure, surface morphology, elemental composition, transmittance as well as conductivity of thin films were strongly dependent on deposition parameters. The optimum parameters for CIGS thin films were obtained at a power 100 W, pressure 5 mT and substrate temperature 500 °C. XRD revealed that thin film deposited at above said parameters was polycrystalline in nature with larger crystallite size (32 nm) and low dislocation density (0.97×10¹⁵ lines m⁻²). The deposited film also showed preferred orientation along (112) plane. The morphology of the film depicted by FE-SEM was compact and uniform without any micro cracks and pits. The deposited film exhibited good stoichiometry (Ga/In+Ga=0.19 and In/In+Ga=0.8) with desired Cu/In+Ga ratio (0.92), which is essential for high efficiency solar cells. Transmittance of deposited film was found to be very low (1.09%). The absorption coefficient of film was ~10⁵ cm⁻¹ for high energy photon. The band gap of CIGS thin film evaluated from transmission data was found to be 1.13 eV which is optimum for solar cell application. The electrical conductivity (7.87 Ω⁻¹ cm⁻¹) of deposited CIGS thin film at optimum parameters was also high enough for practical purpose.     

准分子激光对掺杂SnO2气敏元件性能的影响

一定能量密度的准分子激光作用于掺杂ＳｎＯ２烧结型气敏元件敏感材料表面后，元件性能发生了显著的变化。元件电阻和对气体的灵敏度比作用前有明显的增加，同时材料表面颜色生变化，分析认为该过程中由于短脉冲的准分子激光作用，使ＳｎＯ２材料快速升温熔化并快速冷凝重构，导致表面变性，从而引起了材料电性能和气体敏感性能的变化。     

The role of oxidizing agents in the structural and morphological properties of CeO2 nanoparticles

Cerium oxide (CeO₂) nanoparticles with good crystallinity and smooth surface are prepared by chemical precipitation method with different bases (NH₃, NaOH and KOH) using cerium nitrate as a source material. The effect of precipitating agents on the growth of cerium oxide nanoparticles are investigated by Photoluminescence (PL), X-ray diffraction (XRD), Fourier transform-infra red spectroscopy (FTIR), thermo gravimetric–differential thermal analysis (TG-DTA), Scanning electron microscope (SEM), Transmission electron microscope (TEM), and X-ray Photoelectron Spectroscopy (XPS). Cubic fluorite crystallites are detected by XRD pattern with preferred orientation along (1 1 1) direction. PL spectra revealed the presence of a strong and broad emission band at425 nm due to the blue shift in the visible region. The broad band below 700 cm⁻¹ is due to the envelope of the phonon band of metal oxide (Ce–O) network as revealed by the IR spectra. The TG-DTA curves revealed that the total weight loss of the samples is 19.67% when the samples are heated upto 800 °C. SEM images exhibits weakly agglomerated spheroid crystallites are obtained with the typical size in the range 10–50 nm. TEM images display that the particles are nearly spherical and square in shape with diameter 8–12 nm. XPS spectrum confirms the existence of Ce⁴⁺ oxidation states in CeO₂samples.     

Effect of annealing and HNO3-treatment on the electrical properties of transparent conducting carbon nanotube films

Thin films of single-walled carbon nanotubes (SWCNTs) were prepared by vacuum filtration. The electrical behavior of the as-prepared, annealed and HNO₃-treated SWCNT thin films was investigated. The results demonstrated that the post-treatments play an important role in modifying the electrical properties of the SWCNT thin films. The changes in the electrical properties upon annealing and HNO₃-treatment were attributed to the chemical-charge-transfer. A room-temperature ethanol alcohol sensor based on the SWCNT film has been demonstrated.     

衬底偏压对HWCVD制备纳米晶硅薄膜结晶性的影响

通过在热丝化学气相沉积(HWCVD)制备纳米晶硅 薄膜过程中施加衬底偏压,研 究衬底偏压对HWCVD制备纳米晶硅薄膜结晶性能的影响。利用拉曼(Raman)光谱,X射线 衍射(XRD)和扫描电子显微镜(SEM)对所制备的纳米晶硅薄膜的结构性能进行分析。结果表 明,与未施加衬底偏压的薄膜相比,当衬底偏压为－300V时,薄膜 的晶化率由42.2%升高至 46.2%;当衬底偏压升高至－600V时,晶化率 又降至40.6%;未施加衬底偏压与施加－300V 偏压的纳米晶硅薄膜表面由长约200nm、宽约100nm的晶粒构成,－600V衬底偏压的薄 膜表面晶粒尺寸明显变小,并且出现大量非常细小的晶粒。分析产生上述现象的原因,主要 与 高温热丝发射电子、电子在电场作用下加速运动并与反应气体、基团碰撞发生能量传递有关 。     

The effects of CO,water vapor and surface temperature on the conductivity of a SnO2 gas sensor

It is shown that the conductivity of a SnO₂ gas sensor depends on the concentration of CO and H₂O in the atmosphere n which it is placed. The experimental data can be explained in a consistent manner by hypothesizing that 1) adsorbed oxygen depletes the surface electron concentration and therefore decreases the conductivity; 2) adsorbed water causes electrons to accumulate at the surface and therefore increases the conductivity; 3) CO increases the conductivity by removing adsorbed oxygen by reacting with it to form CO₂; and 4) adsorbed water catalyzes the CO to CO₂ reaction.     

Colloidal synthesis of copper cadmium sulphide (CuCdS2) nanoparticles and its structural,optical and morphological properties

Oleylamine mediated CuCdS₂ nanoparticles were synthesized by the colloidal hot injection method at 230 °C. Structural analysis reveals that the nanoparticles exhibit wurtzite phase with high crystallinity. The average crystallite size of the nanoparticles was calculated as 40 nm. Optical band gap of the synthesized nanoparticles was calculated from UV-vis absorption spectrum as ~1.70 eV. Nanorods and nanoplates like morphologies with well-defined boundaries of CuCdS₂ nanoparticles were observed from scanning electron microscope analysis. Purity of the synthesized nanoparticles was confirmed using energy dispersive X-ray analysis. Vibrational modes of CuCdS₂ nanoparticles were observed from the Raman spectroscopy analysis. X-ray photon spectroscopy analysis confirms the oxidation states of the elements present in the nanoparticles. The possible mechanism involved in the formation and morphology of CuCdS₂ nanoparticles was discussed.     

Annealing temperature dependent structural and optical properties of electrodeposited CdSe thin films

Cadmium selenide films were synthesized using simple electrodeposition method on indium tin oxide coated glass substrates. The synthesized films were post annealed at 200 °C, 300 °C and 400 °C. X-ray diffraction of the films showed the hexagonal structure with crystallite size <3 nm for as deposited films and 3–25 nm for annealed films. The surface morphology of films using field emission scanning electron microscopy showed granular surface. The high resolution transmission electron microscopy of a crystallite of the film revealed lattice fringes which measured lattice spacing of 3.13 Å corresponding to (002) plane, indicating the lattice contraction effect, due to small size of CdSe nanocrystallite. The calculation of optical band gap using UV–visible absorption spectrum showed strong red-shift with increase in crystallite size, indicating to the charge confinement in CdSe nanocrystallite.     

Study of structural and optical properties of nanostructured V2O5 thin films doped with fluorine

In this study, vanadium oxide (V₂O₅) was doped with different percentages of fluorine (F) and deposited on glass substrates by using spray pyrolysis method. The substrate temperature during the film deposition was kept constant at 450 °C. The obtained nanostructured thin films were characterised by X-ray Diffraction (XRD), UV–visible spectroscopy, and Scanning Electron Microscopy (SEM). The XRD results showed that F doped films are polycrystalline with main phase of β-V₂O₅ and with preferred orientation along (200). Increasing dopant to 30% improved crystallinity, but for more doping, the structure of samples tended to be amorphous. VF₂ phase was also observed when doping of F was increased to more than 10%. The incorporation of fluorine in nano-layers led to a decrease in optical absorption by 1.3 a.u. and an increase in band gap of energy from 2.23 to 2.83 eV. SEM images showed that the shape of grains was spherical with 10% doping and changed to bacilliform with 70% F concentration. The cyclic voltammetry results obtained for different samples showed expanded anodic and cathodic peaks for the undoped sample. The samples prepared with 20% and 40% F-doping level had milder anodic and cathodic peaks. However, by increasing the dopant to 70%, the peaks were expanded. The thin film with 40% F-doping showed the least resistance, but the resistance increased dramatically with 70% F dopant concentrations.     

Thermally induced structural changes and optical properties of tin dioxide nanoparticles synthesized by a conventional precipitation method

Tin dioxide (SnO₂) nanoparticles were synthesized by a conventional precipitation method using the reaction between tin chloride pentahydrate and ammonia solutions. The obtained powders were calcined at varied temperatures from 300 to 1050 °C, and then characterized by using thermogravimetric analysis, differential thermal analysis and Fourier transformation infrared spectroscopy. The average crystallite size, determined by x-ray diffraction, was found to be in the range of 3.45–23.5 nm. The analysis exhibited a tetragonal phase. The activation energy of crystal growth was calculated and found to be 12.12 kJ/mol. The microstructure of nanoparticles was examined by high resolution transmission electron microscopy. Optical properties were investigated by a UV–vis absorption spectrophotometer. The calculated optical band gap lies between 4.75–4.25 eV as a result of increasing the calcination temperatures and crystallite size.     

Effect of tantalum doping on the structural and optical properties of RF magnetron sputtered indium oxide thin films

Tantalum doped indium oxide films are prepared by RF magnetron sputtering technique and the films are annealed in air at 300 °C. The effect of Ta doping on the structural, morphological, and optical properties of the annealed films are studied using techniques like X-ray diffraction (XRD), atomic force microscopy (AFM), field emission scanning electron microscopy (FESEM), EDX analysis, micro-Raman, UV–visible and photoluminescence spectroscopy and electrical measurements. The XRD patterns present a cubic bixbyite structure for all the films with preferred orientation along the (222) plane. The lattice constant estimation presents a reduction in lattice size with Ta doping. The W–H plot shows a tensile strain for all the films and also indicates the presence of strain induced broadening of the XRD peaks. The Raman spectra present all the characteristic modes of In₂O₃ cubic bixbyite phase. FESEM and AFM images show the uniform and dense distribution of smaller grains in the films. All the films show high transmittance (above 85%) in the 400–900 nm region. Electrical measurement shows a systematic increase of carrier concentration and electrical conductivity with increase in Ta doping concentration. Band gap energy increases with increase in Ta doping concentration. All the films show intense PL emission in the UV region.     

Influence of working pressure on the structural,optical and electrical properties of sputter deposited AZO thin films

Highly oriented crystalline aluminum doped zinc oxide (AZO) films were sputter deposited on glass substrates and a systematic investigation on the as deposited and etched films was reported for its further application in silicon thin film solar cell. Influence of the deposition pressure (from 2 to 8 mTorr) and post-annealing temperature (at 400 °C for 5 min) on the structural, optical and electrical properties of the as-deposited and etched samples were analyzed. The optimum condition for its reproducibility and large area deposition is determined and found that the depositions made at 8 mTorr at 200 W having the distance from source to substrate of 9 cm. All the AZO films exhibited a c-axis preferred orientation perpendicular to the substrate and their crystallinity was improved after annealing. From the XRD pattern the grain size, stress and strain of the films were evaluated and there is no drastic variation. Optical transmittance, resistivity, Hall mobility and carrier concentration for the as deposited and etched-annealed films were found to improve from 79 to 82%; 2.97 to 3.14×10⁻⁴ Ω cm; 25 to 38 cm²/V s; 8.39 to 5.96×10²⁰/cm³ respectively. Based on the triangle diagram between figure of merit and Hall mobility, we obtained a balance of point between the electrical and optical properties to select the deposition condition of film for device application.