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.     

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.     

Structural and optoelectronic properties of nanostructured TiO2 thin films with annealing

About 480 nm thick titanium oxide (TiO₂) thin films have been deposited by electron beam evaporation followed by annealing in air at 300–600 °C with a step of 100 °C for a period of 2 h. Optical, electrical and structural properties are studied as a function of annealing temperature. All the films are crystalline (having tetragonal anatase structure) with small amount of amorphous phase. Crystallinity of the films improves with annealing at elevated temperatures. XRD and FESEM results suggest that the films are composed of nanoparticles of 25–35 nm. Raman analysis and optical measurements suggest quantum confinement effects since Raman peaks of the as-deposited films are blue-shifted as compared to those for bulk TiO₂ Optical band gap energy of the as-deposited TiO₂ film is 3.24 eV, which decreases to about 3.09 eV after annealing at 600 °C. Refractive index of the as-deposited TiO₂ film is 2.26, which increases to about 2.32 after annealing at 600 °C. However the films annealed at 500 °C present peculiar behavior as their band gap increases to the highest value of 3.27 eV whereas refractive index, RMS roughness and dc-resistance illustrate a drop as compared to all other films. Illumination to sunlight decreases the dc-resistance of the as-deposited and annealed films as compared to dark measurements possibly due to charge carrier enhancement by photon absorption.     

Effects of annealing on the structural and optical properties of zinc sulfide thin films deposited by ion beam sputtering

We report the structural and optical properties of ZnS thin films fabricated by ion-beam sputtering. X-ray diffraction (XRD) and transmission electron microscopy (TEM) results revealed a polycrystalline ZnS film with zinc blende phase as manifested by diffraction from the (111), (220) and (311) planes. Annealing resulted in the appearance of a metastable wurtzite phase with a concentration up to 26.6%. An energy bandgap, estimated from absorption spectra, was found to vary between 3.32 and 3.40 eV. The lower energy of this bandgap, as compared to bulk ZnS, is associated with the structural point defects along with mixed zinc blende and wurtzite phases of the polycrystalline ZnS films. Ion beam sputtering deposition can be used to tune the optical bandgap for potential applications in optoelectronic materials.     

Effect of annealing temperature on optical and electrical properties of lead sulfide thin films

Lead sulfide (PbS) thin films with 150 nm thickness were prepared onto ultra-clean quartz substrate by the RF-sputtering deposition method. Deposited thin films of PbS were annealed at different temperatures 100 °C, 150 °C, 200 °C, 250 °C and 300 °C. X-ray diffraction pattern of thin films revealed that thin films crystallized at 150 °C. Crystalline thin films had cubic phase and rock salt structure. The average crystallite size of crystalline thin films was 22 nm, 28 nm and 29 nm for 150 °C, 200 °C and 250 °C respectively. From 150 °C to 250 °C increase in annealing temperature leads to increase in crystallite arrangement. FESEM images of thin films revealed that crystallite arrangement improved by increasing annealing temperature up to 250 °C. Increase in DC electrical conductivity by increasing temperature confirmed the semiconductor nature of crystalline thin films. Increase in dark current by increasing annealing temperature showed the effect of crystallite arrangement on carrier transport. Photosensitivity decreased by increasing annealing temperature for crystalline thin films that it was explained at the base of thermal quenching of photoconductivity and adsorption of oxygen at the surface of thin films that leads to the formation of PbO at higher temperatures.     

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.     

Annealing effect on structural and optical properties of Se87.5Te10Sn2.5 thin films

Thin films of Se_87.5Te₁₀Sn_2.5 were prepared by vacuum thermal evaporation technique. Various optical constants were calculated for the studied composition. The mechanism of the optical absorption follows the rule of direct transition. It was found that the optical energy gap (E_g) decreases from 2.26 to 1.79 eV with increasing the annealing temperature from 340 to 450 K. This result can be interpreted by the Davis and Mott model. On the other hand, the maximum value of the refractive index (n) is shifted towards the long wavelength by increasing the annealing temperature. In addition, the high frequency dielectric constant (ε_L) increased from 31.26 to 48.11 whereas the ratio of the free carriers concentration to its effective of mass N/m^⁎ decreased from 4.3 to 2.09 (×10⁵⁷ (m⁻³ Kg⁻¹)). The influence of annealed temperature on the structure was studied by using the X-ray diffraction (XRD) and scanning electron microscopy (SEM). The XRD studies show that the as-deposited films are amorphous in nature, but the crystallinity improved with increasing the annealing temperature. Furthermore the particle size and crystallinity increased whereas the dislocation and strains decreased with increasing the annealing temperature. SEM examination showed that the annealing temperature induced changes in the morphology of the as-deposited film.     

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.     

Mg and Al co-doping of ZnO thin films: Effect on ultraviolet photoconductivity

Thin films of Zinc Oxide were deposited by the sol-gel technique on glass substrates. The films were doped with Al, Mg or co-doped with both by introduction of appropriate compounds in the solution before dip-coating and annealing in air at 500 °C. Energy Dispersive X-Ray Spectroscopy was employed to measure the dopant incorporation. X-ray diffraction studies indicate that Mg doping increases grain size, while Al doping reduces it. Photoluminescence (PL) measurements indicate that undoped and Al-doped films show, along with a broad near band-edge (NBE) peak, additional peaks at longer wavelengths related to various defect states. However Mg doped films show only a sharp NBE peak, which is blue shifted compared to undoped ZnO, and there are no prominent sub band gap luminescence peaks. This is also the case for Mg and Al co-doped ZnO samples, provided the Mg content is low. Photocurrent measurements were carried out using silver contacts using a De source under atmospheric conditions. Undoped and Mg doped ZnO films showed high resistances and low photocurrent levels. With low Al doping, both the dark current and the photocurrent increase significantly, but the films show very long photocurrent transients. With optimized concentration of Mg/Al co-doping in ZnO, the photocurrent increased by ~98 times compared to ZnO films doped only with Mg. Simultaneously, the photocurrent transients became ~44 times faster than ZnO films doped only with Al.     

Antimony sulfide (Sb2S3) thin films by pulse electrodeposition: Effect of thermal treatment on structural,optical and electrical properties

Antimony sulfide films have been deposited by pulse electrodeposition on Fluorine doped SnO₂ coated glass substrates from aqueous solutions containing SbCl₃ and Na₂S₂O₃. The crystalline structure of the films was characterized by X-ray diffraction, Raman spectroscopy and TEM analysis. The deposited films were amorphous and upon annealing in nitrogen/sulfur atmosphere at 250 °C for 30 min, the films started to become crystalline with X-ray diffraction pattern matching that of stibnite, Sb₂S₃, (JCPDS 6-0474). AFM images revealed that Sb₂S₃ films have uniformly distributed grains on the surface and the grain agglomeration occurs with annealing. The optical band gap calculated from the transmittance and the reflectance studies were 2.2 and 1.65 eV for as deposited and 300 °C annealed films, respectively. The annealed films were photosensitive and exhibited photo-to-dark current ratio of two orders of magnitude at 1 kW/m² tungsten halogen radiation.     

Pulse electrodeposited copper indium sulpho selenide films and their properties

Copper indium sulpho selenide films of different composition were deposited by the pulse plating technique at 50% duty cycle (15 s ON and 15 s OFF). X-ray diffraction studies indicated the formation of single phase chalcopyrite copper indium sulpho selenide films. Transmission Electron Microscope studies indicated that the grain size increased from 10 nm–40 nm as the selenium content increased. The band gap of the films was in the range of 0.95 eV–1.44 eV. Room temperature resistivity of the films is in the range of 16.0 Ω cm–33.0 Ω cm. Films of different composition used in photoelectrochemical cells have exhibited photo output. Films of composition, CuInS_0.9Se_0.1 have exhibited maximum output, a V_OC of 0.74 V, J_SC of 18.50 mA cm^?2, ff of 0.75 and efficiency of 11.40% for 60 mW cm^?2 illumination.     

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.     

A study of the physical properties of sprayed CdS thin films

CdS films have been prepared by spray pyrolysis and characterized by several methods. The spray solution is made of cadmium chloride or cadmium acetate and thiourea. Optical and compositional properties and structure of the CdS films have been investigated. An analysis of the film's structure, preferred cyrstallographic orientation and presence of impurity phases have been obtained using X-ray diffraction technique as well as infrared spectroscopy. The visible absorption measurements have been carried out for the study of the impurity phases. Quantitative Auger analysis shows the composition of the spray solution and a post-spray heat treatment have also been investigated.     

Thickness dependent structural and optical properties of In/Te bilayer thin films

In_xTe_y thin films have been prepared from In/Te bilayer by sequential thermal evaporation. The samples were analyzed by x-ray diffraction (XRD), optical transmittance spectra and scanning electron microscopy (SEM) and energy dispersive x-ray spectroscopy (EDX) in order to investigate structural, optical properties, surface morphology and elemental composition of the prepared films. XRD spectra reveal that all films exhibit mixed phases of In₂Te₃ and In₂Te₅. Increase in grain size with film increase in thickness was observed. The surface was highly porous as observed by SEM analysis. Band gap energy of In_xTe_y system is found to decrease with increase in film thickness.     

衬底温度对CZTSSe薄膜结构特性的影响

采用热蒸发法制备铟锌锡硫(CZTSSe)薄膜。采用低 温一步 法在300℃衬底温度下制备CZTSSe薄膜;采用两步法,即在衬底温度 分别为300℃制备CZTSSe 薄膜;将衬底温度设定为480℃不变,一步蒸发沉积CZTSSe薄膜。通 过对X射线衍射(XRD)、 扫描电镜(SEM)、拉曼谱对比发现,在300℃低温下一步法和300℃ 、480℃两 步法沉积的薄膜表面粗糙,碎小晶粒较多;在480℃一步高温法制备 的薄膜表面平整, 晶粒大小均匀,3个衍射峰的半高峰宽变窄,薄膜的结晶质量得到 改善,且没有发现其它杂相的拉曼特征峰,沉积出适合作为制备CZTSSe薄膜太阳电池的 吸收层。     

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.     

The effect of Fe3+-doped on structure and optical properties of mesoporous Al2O3/SiO2 composite

The composition of 98.0(Al_1.9Fe_0.1O₃)/2.0SiO₂ was synthesized by modifying auto-combustion method and the effect of calcination temperature on structure and optical properties were studied. The prepared powders were characterized by X-ray diffraction (XRD) patterns, X-ray fluorescence (XRF) spectrometry, Ultraviolet-visible (UV–vis) spectra and Fourier transform infrared (FTIR) spectroscopy. The particle size distribution and the specific surface area of nanoparticles were studied using Transmission electron microscopy (TEM) and BET analysis technique. Adopting Kramers–Kronig relation, FTIR and UV–vis spectra, the optical constants of nano-alumina, including optical band gap (E_g), refractive index (n), extinction coefficients (k), real (ε₁) and imaginary parts (ε₂) of dielectric function were obtained. The results of optical band gap values indicate quantum confinement effect. The energy loss functions were determined to show loss of energy that transmit through a solid.     

Brush electrodeposited silver indium selenide films and their optical characteristics

Silver indium selenide films were brush electrodeposited on tin oxide coated glass substrates at different substrate temperatures. The films were single phase with chalcopyrite structure. Optical absorption measurements indicated a band gap in the range of 1.20–1.30 eV with decrease of substrate temperature. Transmission spectra exhibited interference fringes. Using the envelope method, calculated values of refractive index at 850 nm decreased from 3.53 to 2.62 with decrease of substrate temperature. From the refractive index data, the value of N/m^⁎ was estimated to be in the range of 0.89–1.22. Optical data were analyzed by the single-effective oscillator model, and the single oscillator energy as well as the dispersion energy was estimated. The single oscillator energy decreased from 1.83 eV to 1.68 eV with the increase of substrate temperature. The dispersion energy increased from 5.42 eV to 12.25 eV with the increase of substrate temperature.     

Structural and the optical dispersion parameters of nano-CdTe thin film/flexible substrate

CdTe thin films of different thicknesses were deposited on polymer substrates for flexible optical devices applications. X-ray diffractogram of different thicknesses for CdTe films are measured and their patterns exhibit polycrystalline nature with a preferential orientation along the (111) plane. The optical constants of CdTe films were calculated based on the measured transmittance spectral data using Swanepoel's method in the wavelength range 400–2500 nm. The refractive index n and absorption index k were calculated and the refractive index exhibits a normal dispersion. The refractive index dispersion data followed the Wemple–DiDomenico model based on single oscillator. The oscillator dispersion parameters and the refractive index no. at zero photon energy were determined. The possible optical transition in these films is found to be allowed direct transition with energy gap increase from 1.46 to 1.60 eV with the increase in the film thickness. CdTe/flexible substrates are good candidates in optoelectronic devices     

Effects of annealing on nanocrystalline Bi2S3 thin films prepared by chemical bath deposition

Nanocrystalline Bi₂S₃ thin films are deposited on tin chloride treated glass substrate from the solution containing bismuth nitrate, triethanolamine (TEA) and thioacetamide (TAM) at a bath temperature 318 K. The prepared films are subsequently annealed at different temperatures for studying the effect of thermal treatment on the structural, surface morphology, optical and electrical properties of the films. The X-ray diffraction studies affirmed that the deposited films are orthorhombic structures with average crystallites size of 14 nm to 28 nm. The scanning electron microscopy (SEM) images revealed that the films comprise of grains of spherical shape of unequal size. It is also observed that the small particles aggregate together to form a larger cluster. The average grain sizes determined from the TEM images are smaller than the crystallites size obtained from the XRD studies. The optical band gap of the films has been estimated to be 2.24–2.05 eV for the as-prepared and annealed films, respectively. The electrical conductivity of the as prepared Bi₂S₃ films at room temperature is found to be in the order of 10⁻³ Ω⁻¹ m⁻¹.