Synthesis and effect of post-deposition thermal annealing on morphological and optical properties of ZnO thin film

Zinc oxide thin films have been deposited on glass substrates by the chemical bath deposition method; a surfactant, cetyltrimethylammonium bromide (CTAB); was used as capping agent. The films were annealed at two different temperatures: 200 and 300 °C. The structural features were investigated by X-ray diffraction analysis which exhibited hexagonal wurtzite structures along with c-axis orientations. Crystallite size was estimated and found to be around 33–41 nm. The effect of post-deposition thermal annealing on the morphological and optical properties has been investigated by scanning electron microscopy and photoluminescence spectra at room temperature. The band gap energies of uncapped and CTAB-capped ZnO films were found to be 3.28 and 3.48 eV, respectively.     

Effect of post‐deposition annealing on surface morphology and gas sensing properties of palladium phthalocyanine thin films

The effect of post‐deposition annealing on surface morphology and gas sensing properties of palladium phthalocyanine (PdPc) nanostructured thin films has been studied. PdPc thin films were deposited on polyborosilicate substrate by thermal evaporation technique at room temperature. The surface morphology of thin films was investigated by SEM, X‐ray diffraction, and optical absorption. X‐ray diffraction patterns showed a phase transition from α to β based on post‐deposition annealing at temperatures above 200 °C. The SEM and optical absorption confirmed that annealing strongly influenced the surface morphology of nanostructured thin films. Sandwich devices (Au|PdPc|Al) were fabricated and exposed to different concentrations of NO₂ and NH₃ as oxidizing and reducing gases at different temperatures, and the sensitivity of devices were obtained versus gases. Obtained results showed α‐PdPc thin film devices had higher sensitivity in comparison with devices in β‐phase. In particular, it was found that the sensitivity of devices is temperature dependent and the best operating temperature range of devices was measured at about 90–100 °C. Devices showed good reversibility, response, and recovery time at room temperature. Finally, the stability of sensors was investigated for a period of about 1 year; results showed that the sensors were stable for 2 months and lost about 30% of their sensitivity after 1 year. Copyright © 2012 John Wiley & Sons, Ltd.     

Effect of swift heavy ion irradiation on the physical properties of CuIn(S0.4Se0.6)2 alloy thin films prepared by solution growth technique

Alloy thin films of CuIn(S_0.4Se_0.6)₂ material were deposited using the solution growth technique. The various deposition parameters such as pH of solution, time, concentration of ions and temperature have been optimized for the device grade thin films. The as-deposited films were annealed in a rapid thermal annealing (RTA) system at 450 °C in air for 5 min and subjected to high-energy Ag ion irradiations. Ag ion irradiation has been performed with an energy of 100 MeV at a fluency of 5×10¹² ions/cm² on the thin film. The changes in optical and electrical properties that occurred before and after post-deposition treatments in CuIn(S_0.4Se_0.6)₂ thin films were studied using X-ray diffraction (XRD) and AFM; increase in crystallinity was observed after annealing and irradiation. In addition, structural damages were observed in irradiated thin films. After annealing and irradiation, the surface roughness was seen to be increased. Decrease in resistivity was observed, which is consistent with the optical energy band gap. The results are explained by considering the high energy deposited due to the electronic energy loss upon irradiation, which modified the properties of the material.     

Electrical,optical, and structural characterization of p‐type N‐doped SnO thin films prepared by thermal oxidation of sputtered SnNx thin films

We present a study of electrical and optical properties of nitrogen‐doped tin oxide thin films deposited on glass by the DC Magnetron Sputtering method. The deposition conditions to obtain p‐type thin films were a relative partial pressure between 7% and 11% (N₂ and/or O₂), a total working pressure of 1.8 mTorr and a plasma power of 30 W. The deposited thin films were oxidized after annealing at 250°C for 30 minutes. X‐ray diffraction results showed that the as‐deposited thin films exhibit a Sn tetragonal structure, and after annealing, they showed SnO tetragonal structure. X‐ray photoelectron spectroscopy results showed the presence of nitrogen in the samples before and after annealing. The measured physical parameters of the thin films were optical band gap between 1.92 and 2.68 eV, resistivity between 0.52 and 5.46 Ωcm, a concentration of p‐type carriers between 10¹⁸ and 10¹⁹ cm^?3, and a Hall mobility between 0.1 and 1.94 cm²V^?1s^?1. These thin films were used to fabricate p‐type thin film transistors.     

Influence of surfactant and annealing temperature on optical properties of sol–gel derived nano-crystalline TiO2 thin films

Titanium dioxide thin films have been synthesized by sol–gel spin coating technique on glass and silicon substrates with and without surfactant polyethylene glycol (PEG). XRD and SEM results confirm the presence of nano-crystalline (anatase) phase at an annealing temperature of 300 °C. The influence of surfactant and annealing temperature on optical properties of TiO₂ thin films has been studied. Optical constants and film thickness were estimated by Swanepoel's (envelope) method and by ellipsometric measurements in the visible spectral range. The optical transmittance and reflectance were found to decrease with an increase in PEG percentage. Refractive index of the films decreased and film thickness increased with the increase in percentage of surfactant. The refractive index of the un-doped TiO₂ films was estimated at different annealing temperatures and it has increased with the increasing annealing temperature. The optical band gap of pure TiO₂ films was estimated by Tauc's method at different annealing temperature.     

Microwave assisted novel MoBi2S5 nanoflowers: Synthesis,characterization, photoelectrochemical performance

In the present article, we have studied the effect of post annealing treatment on microstructural, optical and photoelectrochemical (PEC) properties of MoBi₂S₅ thin films synthesized by microwave assisted technique. The synthesized thin films are vacuum annealed for 4 h at 473 K temperature. The X-ray diffraction (XRD), energy dispersive X-ray spectroscopy (EDS), scanning electron microscopy (SEM) and UV–Vis–NIR spectrophotometer techniques were used for characterization of the as deposited and annealed MoBi₂S₅ thin films. The XRD patterns confirm the synthesized and annealed thin films have nanocrystalline nature with rhombohedral-orthorhombic crystal structure. SEM micrographs indicate that, nanoflowers exhibit sharper end after annealing. The optical absorption study illustrates that the optical band gap energy has been decrease from 2.0 eV to 1.75 eV with annealing. Finally, applicability of synthesized thin films has been checked for PEC property. The J-V curves revealed that synthesized thin film photoanodes are suitable for PEC cell application. As well, used simple, economical method has great potential for synthesis of various thin film materials.     

Preparation of <Emphasis Type="Italic">p</Emphasis>-type conducting transparent CuCrO<Subscript>2</Subscript> and CuAl<Subscript>0.5</Subscript>Cr<Subscript>0.5</Subscript>O<Subscript>2</Subscript> thin films by sol–gel processing

CuCrO₂ and CuAl_0.5Cr_0.5O₂ thin films were prepared by sol–gel processing and subsequent two-step annealing in air and inert gas atmosphere. Phase pure films with delafossite structure were obtained by adjusting the respective temperatures. The related phase development strongly affects the optical and electrical performance, giving leeway for optimization. The resulting CuCrO₂ (16 Ωcm, transmittance 21%) and CuAl_0.5Cr_0.5O₂ (11 Ωcm, transmittance 49%) films showed p-type conductivity by their positive Seebeck coefficients. The microstructure of the systems was characterized by scanning and transmission electron microscopy and correlated to the growth of different crystalline phases during the annealing steps. Thereby, crystal thermodynamics also affects the respective film performance, alleviating delafossite formation from the amorphous phase.     

Microstructure and electrical properties of BaTiO<Subscript>3</Subscript> and (Ba,Sr)TiO<Subscript>3</Subscript> ferroelectric thin films on nickel electrodes

Nickel thin films have been sputtered on standard Si/SiO₂ substrates with TiO₂ as an adhesive layer. The thermal stability of these substrates was analyzed. SEM images show an increase in grain size with annealing temperature. They were found to be stable till 800°C, beyond which the nickel layer disintegrated. These substrates were used for deposition of BaTiO₃ and (Ba,Sr)TiO₃ dielectric thin films under a reducing atmosphere. The dielectric thin films were processed with various pyrolysis and annealing temperatures in order to optimize the dielectric properties. Increased pyrolysis temperatures showed an increase in the grain size. Results on these nickelised substrates were finally compared with dielectric films deposited on platinized silicon substrates under identical conditions but crystallized in an oxygen atmosphere.     

Preparation and characterization of CuAlO2 transparent thin films prepared by chemical solution deposition method

CuAlO₂ thin films were prepared on quartz glass and sapphire substrates by chemical solution deposition method using copper acetate monohydrate, aluminum nitrate nonahydrate and 2-methoxyethanol as starting precursor and solvent. The effects of annealing temperature on the structural, morphological, electrical and optical properties have been studied. Via the optimized annealing treatment condition, CuAlO₂ film annealed at 850 °C in nitrogen flow of 400sccm under atmosphere pressure exhibits the best performance with the lowest room temperature resistivity of 3.6 × 10² Ω cm and the highest optical transmission in the visible region (>70% at around 600 nm wavelength). CuAl₂O₄ and CuO phases, not CuAlO₂ phase are obtained when annealing temperature is lower than 850 °C. However, a further increase of annealing temperature weakens the crystallization quality and deteriorates the surface morphology of CuAlO₂ films as the annealing temperature exceeds 850 °C, leading to an increase in the resistivity and a decrease of the optical transmission in the visible region of CuAlO₂ films.     

CuInS2：两步电沉积制备及性能

采用恒电位沉积法制备铜铟合金预制膜,并存管式炉中通过固态源蒸发硫化预制膜得到CuInS:薄膜.通过扫描电镜(SEM)、能量色散谱仪(EDS)和X射线衍射仪(XRD)对CuInS2薄膜的表而形貌、截面厚度、成分组成和薄膜的组织结构进行了研究,并利用紫外可见光吸收谱仪(UV-Vis)研究了不同硫化温度对CuInS:薄膜的形貌及其光学吸收性质的影响.结果表明:不同的退火温度能够影响CuInS:薄膜的表面形貌以及带隙的大小,从而影响其光学吸收特性.     

Fabrication and optical conductivities of strained epitaxial NaxCoO2 thin films: x=0.5, 0.7

Epitaxial γ phase-Na_xCoO₂ thin films were deposited on (001) sapphire by the pulsed laser deposition method. To fabricate epitaxial Na_0.5CoO₂ thin films, we used a solution of iodine-dissolved acetonitrile and obtained an epitaxial Na_0.5CoO₂ thin film with a high crystallinity because of Na deintercalation of epitaxial Na_0.7CoO₂. From the spectroscopic ellipsometry analysis, we obtained the optical constants as well as the optical conductivities for the Na_0.5CoO₂ and Na_0.7CoO₂ thin films. The energy splitting between e_g and a_1g increased because of the structural strain of the Na_0.7CoO₂ thin film. It is inferred that the structural strain is the source for the lower resistivity and the preservation of the strongly correlated system up to 200 K for the Na_0.7CoO₂ thin film. On the other hand, the strain in the Na_0.5CoO₂ thin film was not affected, and the charge-ordering state and the Na content (x=0.5) only cause the charge-ordering state.     

Structure and Optical Properties of 0.1BiFeO3-0.9SrBi2Nb2O9 Thin Films Using a Modified Sol-Gel Technique

Fe-doped SrBi₂Nb₂O₉ precursor solution was synthesized using bismuth nitrate Bi(NO₃)₃·5H₂O, strontium nitrate Sr(NO₃)₂, iron nitrate Fe(NO₃)₃·9H₂O, and niobium ethoxide Nb(OC₂H₅)₅ as starting materials, ethylene glycol monomethyl ether (C₃H₈O₂) as the solvent. 0.1BiFeO₃-0.9SrBi₂Nb₂O₉ thin films were prepared on fused quartz substrates using sol-gel processing. The surface morphology and crystal structure and optical properties of the thin films were investigated. The thin film annealing at 400°C were found to be amorphous, and the thin films crystallize to a perovskite structure after a post-deposition annealing at 600°C for 1 h in air. The grain of thin film was evenly distributed. The thin films exhibit the designed optical transmission, while the optical transition is indirect in nature. Their optical band gap is about 2.5 eV.     

Determination of optical constants of sol‐gel derived Zn0.9Mg0.1O films by spectroscopic ellipsometry with various models

The Zn_0.9Mg_0.1O thin films were prepared on Si (100) substrates by the sol‐gel method. The structural and the optical properties of Zn_0.9Mg_0.1O thin films, submitted to an annealing treatment in the 400–700 °C ranges, are studied by X‐ray diffraction (XRD) and ultraviolet (UV)‐visible spectroscopic ellipsometry (SE). The thickness, refractive index, and extinction coefficient of these films have been determined by analyzing the SE spectra using parameterized dispersion model. Moreover, we made a detailed comparison among various dispersion models and found that the Sellmeier model was superior to others in fitting the ellipsometric spectra in the transparent region. In the interband transition region, point‐by‐point fit was used. The spectral dependence of the refractive index and extinction coefficient was obtained in the photon energy range of 1.5–4.71 eV. The influence of annealing temperature on the refractive index, the extinction coefficient, and the optical bandgap energy was also discussed. We found that the refractive index and the extinction coefficient increase with increasing the annealing temperature, meaning the optical quality of Zn_0.9Mg_0.1O films is improved by annealing. Copyright © 2009 John Wiley & Sons, Ltd.     

Properties of cadmium sulphide thin films deposited from a chemical solution

Cadmium sulphide thin films have been deposited chemically at different temperatures from 50 °C to 100 °C. The composition of the solution was [CdCl₂] = 0.01 M, [Thiourea] = 0.17 M, [NH₄Cl] = 0.036 M and [NH₃] = 0.36 M. Structural, electrical and optical properties were investigated as a function of deposition parameters. The films showed strongly oriented structures and were highly transmitting in the infrared region. Their absorption coefficient was in the range 10⁴ to 10⁵ cm⁻¹ in the visible region. The direct forbidden band had an energy gap of 2.48 eV and the refractive index for high wavelengths was equal to 2.116. The dark resistivities of as-deposited films thicker than 0.5 μm had values from 10³ to 10⁵ Ωcm. These resistivities decreased to about 10 Ωcm after annealing in vaccum or in argon atmosphere at 200 °C for one hour.     

α-Fe<Subscript>2</Subscript>O<Subscript>3</Subscript> thin films by liquid phase deposition: low-cost option for supercapacitor

In the present study, iron oxide (α-Fe₂O₃) thin films with good adhesion on stainless steel substrates are deposited by liquid phase deposition (LPD) technique, which is additive and binder-free. Iron oxyhydroxide (FeOOH) thin films are formed by means of a ligand-exchange equilibrium reaction of metal-fluoro complex ions and an F^?ions consuming reaction by using boric acid (H₃BO₃) as a scavenging agent. These films are annealed at 500 °C to get α-Fe₂O₃ thin films. The transformation from hydrophobic to hydrophilic nature of the films is observed due to annealing. The films are characterized by different techniques. The α-Fe₂O₃ film is checked for electrochemical supercapacitive performance in Na₂SO₃ solutions of various concentrations. Specific capacitance is calculated from cyclic voltammetry at numerous scan rates (5–200) mV s^?1. The highest obtained value of specific capacitance is 582 F g^?1 at 5 mV s^?1 for 0.5 M Na₂SO₃ electrolyte. The maximum values of specific power and specific energy are 6.9 and 53.4 Wh kg^?1 from the charge-discharge curve at the current density 2 mA cm^?2 in 0.5 M Na₂SO₃ electrolyte.     

Structure and optical properties of CVD molybdenum oxide films for electrochromic application

Vibrational and optical properties of MoO₃ thin films have been studied by Raman and infrared spectroscopy. The films were deposited onto Si substrates at a temperature of 150 °C by chemical vapor deposition of Mo(CO)₆ at atmospheric pressure and different amounts of oxygen in the reactor. The Raman and IR spectral analyses show that the as-deposited films are in general amorphous. Post-deposition annealing at 300 and 400 °C leads to crystallization and the MoO₃ film structure is a mixture of orthorhombic and monoclinic MoO₃ modifications. Transformation of the monoclinic crystallographic modification to a thoroughly orthorhombic layered structure is observed for films heated at temperatures above 400 °C. Electronic Publication     

Preparation of (1? x %)(Na0.5Bi0.5)TiO3– x %SrTiO3 thin films by a sol–gel method for dielectric tunable applications

(1−x%)(Na_0.5Bi_0.5)TiO₃–x%SrTiO₃ (NBTSx) thin films were deposited on Pt/TiO₂/SiO₂/Si substrates by a spin-on sol–gel method and rapid thermal annealing. The stock solutions were prepared using sodium acetate, bismuth acetate, strontium acetate, and titanium n-butoxide as precursors, ethanol, and acetic acid as solvents and acetylacetone as the chelating agent. The thermal treatment conditions were determined by thermal analyses of the dry gel powders derived from the stock solutions. Structure and dielectric tunable properties of the films were studied as functions of Sr concentration. NBTSx films exhibit the perovskite structure of a pseudo-cubic symmetry with the lattice parameters increasing with increasing Sr concentration. It was found that the substitution of Sr in Na_0.5Bi_0.5TiO₃ may greatly reduce the dielectric loss while decrease the tunability at the same time. The best figure of merit was achieved in NBTS80 films. The results were discussed and compared with related materials.     

Chemical Solution Deposition of ZnO Thin Films by an Aqueous Solution Gel Precursor Route

An aqueous chemical solution deposition method was used to prepare thin films of ZnO on SiO₂/Si (1 1 1) substrates. Starting from an aqueous solution of Zn acetate, citric acid and ammonia, very thin films could be deposited by spin coating. Heating parameters, necessary for thin film annealing, were determined using FTIR experiments on dried gel precursors, heated up to different temperatures. The morphology and the thickness of the films were investigated by SEM. It is found that homogeneous thin films with grain sizes of about 20 nm are formed. XRD experiments show that there is an indication that the films, crystallized at 500°C, exhibit preferential grain growth along the c-axis.     

Structure and dielectric properties of HfO<Subscript>2</Subscript> films prepared by a sol–gel route

Mono- and multilayer HfO₂ sol–gel thin films have been deposited on silicon wafers by dip-coating technique using a solution based on hafnium ethoxide as precursor. The densification/crystallization process was achieved by classical annealing between 400 and 600 °C for 0.5 h (after drying at 100 °C). Systematic TEM studies were performed to observe the evolution of the thin film structure depending on the annealing temperature. The overall density of the films was determined from RBS spectrometry correlated with cross section (XTEM) thickness measurements. After annealing at 450 °C the films are amorphous with a nanoporous structure showing also some incipient crystallization. After annealing at 550 °C the films are totally crystallized. The HfO₂ grains grow in colonies having the same crystalline orientation with respect to the film plane, including faceted nanopores. During annealing a nanometric SiO₂ layer is formed at the interface with the silicon substrate; the thickness of this layer increases with the annealing temperature. Capacitive measurements allowed determining the value of the dielectric constant as 25 for four layer films, i.e. very close to the value for the bulk material.     

Photovoltaic Behaviour of Titanyl Phthalocyanine Thin Films and Titania Bilayer Films

Summary: Titanyl phthalocyanine (TiOPc) thin films were prepared using evaporation and surface polymerization by ion-assisted deposition (SPIAD) in a vacuum deposition system. These films were characterized by means of ultraviolet and X-ray photoelectron spectroscopy as well as UV/Vis absorption spectroscopy. Valence band and elemental content indicated that phthalocyanine electronic and chemical structures were largely preserved during SPIAD. Further, bilayer thin films of titania (TiO₂) and SPIAD TiOPc were prepared. TiO₂ film was deposited by reactive magnetron sputtering of TiO₂ target. Study of the structured samples was focused on the optical and electrical properties of the composite films. The films were characterized by non-contact photovoltage measurements and UV-Vis spectroscopy. These results suggest there is a possibility to use these bilayer thin films in photovoltaic solar cells, however further experiments to improve conductivity of the films will be required.