Influence of annealing on the optical properties of 5,10,15,20-tetraphenyl-21H, 23H-porphine iron (III) chloride thin films

Optical constants (refractive index, n, and absorption index, k) of the as-deposited and annealed films of 5,10,15,20-tetraphenyl-21H, 23H-porphine iron (III) chloride (FeTPPCl) have been obtained in the wavelength range 190–2500 nm by using spectrophotometric measurements. The obtained optical constants were used to estimate the type of transition for the as-deposited and annealed films. We present a single oscillator model that describes the dispersion of refractive index. Drude model of free carriers absorption have been described for the analysis the dispersion of refractive index dispersion before and after annealing.     

Birefringence behaviour of annealed silk fibres

Silk fibres were annealed at 140 ° C for different annealing times ranging from 2 to 10h. Refractive indices and birefringence of annealed fibres were measured by two different interferometric methods. An interference polarizing microscope and multiple-beam Fizeau fringes in transmission techniques were used. The scanning electron microscope was used to estimate the geometrical parameters of silk fibres. The behaviour of birefringence for annealed silk fibres showed that the birefringence reach a maximum value when silk was annealed for 5 to 6 h at 140 ° C. The isotropic refractive index of annealed silk is also slightly increased with increasing annealing time. The results obtained clarify the effect of annealing time on the optical behaviour of natural silk fibres. Microinterferograms are given for illustration.     

Optical waveguiding and birefringence properties of sputtered zinc oxide (ZnO) thin films on glass

Thin (≈1 μm), waveguiding and c-axis oriented ZnO films of good optical quality have been fabricated on corning glass substrates by r.f. magnetron reactive sputtering without substrate heating. The optical parameters of the films deposited in different O₂:Ar sputtering gas mixtures were found to vary. The extraordinary and ordinary refractive indices (n_e and n_o respectively) of the ZnO film grown in 60% O₂ and 40% Ar were found to be the highest (n_e=1.9876, n_o=1.9692) and closest to bulk single crystal values, and the birefringence of the film was ≈0.018. The films were annealed at 380 °C in air for 1 h, as a result of which the crystalline quality of the films was found to improve with increase in X-ray density and decrease in stress. While the refractive index decreased, the propagation loss was lowered substantially (3–5 dB/cm) as a result of annealing. The annealed zinc oxide film with minimum stress exhibited lowest loss (3 dB/cm) and highest birefringence (≈0.018). This indicated a correlation between propagation loss and stress.     

Optical properties of Sb2Se3 thin films

The optical constants (the refractive index n and the absorption index k) of Sb₂Se₃ thin films deposited at room temperature on quartz have been calculated in the wavelength range (5000–2000 nm) using a transmission spectrum. Both n and k were found to be practically independent on either time, up to 6 months, or the film thickness in the range of 102–760 nm. Beyond the absorption edge, the absorption is due to allowed indirect and direct transitions with energy gaps of 1.225 and 1.91 eV, respectively. The value of the optical gap depends on the annealing temperature. X-ray analysis showed that the prepared films at room temperature had amorphous structure while the films annealed at 200°C for 1 h were verified to be crystalline.     

Role of annealing temperature on microstructural and electro-optical properties of ITO films produced by sputtering

This study probes the effect of annealing temperature on electrical, optical and microstructural properties of indium tin oxide (ITO) films deposited onto soda lime glass substrates by conventional direct current (DC) magnetron reactive sputtering technique at 100 watt using an ITO ceramic target (In₂O₃:SnO₂, 90:10 wt%) in argon atmosphere at room temperature. The films obtained are exposed to the calcination process at different temperature up to 700 °C. X–ray diffractometer (XRD), ultra violet-visible spectrometer (UV–vis) and atomic force microscopy (AFM) measurements are performed to characterize the samples. Moreover, phase purity, surface morphology, optical and photocatalytic properties of the films are compared with each other. The results obtained show that all the properties depend strongly on the annealing temperature. XRD results indicate that all the samples produced contain the In₂O₃ phase only and exhibit the polycrystalline and cubic bixbite structure with more intensity of diffraction lines with increasing the annealing temperature until 400 °C; in fact the strongest intensity of (222) peak is obtained for the sample annealed at 400 °C, meaning that the sample has the greatest ratio I ₂₂₂/I ₄₀₀ and the maximum grain size (54 nm). As for the AFM results, the sample prepared at 400 °C has the best microstructure with the lower surface roughness. Additionally, the transmittance measurements illustrate that the amplitude of interference oscillation is in the range from 78 (for the film annealed at 400 °C) to 93 % (for the film annealed at 100 °C). The refractive index, packing density, porosity and optical band gap of the ITO thin films are also evaluated from the transmittance spectra. According to the results, the film annealed at 400 °C obtains the better optical properties due to the high refractive index while the film produced at 100 °C exhibits much better photoactivity than the other films as a result of the large optical energy band gap.     

Influence of thermal annealing on optical properties and structure of aluminium oxide thin films by filtered cathodic vacuum arc

Optical and structural properties of aluminium oxide thin films are investigated in the annealing temperature range of 200–900 °C. The changes in optical properties and film structure show the great dependence on the temperature. For the film annealed at low temperatures (from 200 °C to 600 °C), the film optical properties, such as transmittance and optical constants, could be improved by thermal annealing with amorphous structure and smooth surface. However, for the film annealed at higher temperature (e.g. 900 °C), the poor performance of optical properties indicates undesirable application for precise use in optics due to significant changes in both structure and surface roughness. At optimum annealing temperature of 600 °C, the transmittance could reach as high as that of substrate and the film possesses better optical constants (refractive index was 1.73 and extinction coefficient was ∼10⁻⁴ at 550 nm) with remaining amorphous structure and smooth surface.     

Influence of annealing temperature on structural,electrical and optical properties of undoped zinc oxide thin films

The undoped zinc oxide thin films were grown on quartz substrate at a substrate temperature of 750 °C by radio frequency magnetron sputtering and post annealed at different temperatures (600–800 °C) for a period of 30 min. The influence of annealing temperature on the structure, electrical and optical properties of undoped ZnO thin films was investigated by X-ray diffraction, Hall-effect, photoluminescence and optical transmission measurements. Results indicated that the electrical properties of the thin films were extremely sensitive to the annealing temperature and the conduction type could be changed dramatically from n-type to p-type, and finally changed to weak p-type when the temperature increased from 600 to 800 °C. Electrical and photoluminescence results indicate that native defects, such as oxygen and zinc vacancies, could play an important role in determining the conductivity of these nominally undoped ZnO thin films. The conversion of the conduction type was attributed to the competition between Zn vacancy acceptor and oxygen vacancy and interstitial Zn donors. At an intermediate annealing temperature of 750 °C, the film behaves the best p-type characteristic, which has the lowest resistivity of 12 Ωcm, hall mobility of 2.0 cm²/V s and carrier concentration of 1.5 × 10¹⁷ cm^?3. The photoluminescence results indicated that the Zn vacancy might be responsible for the intrinsic better p-type characteristic in ZnO thin films.     

Studies on thermally treated lanthanum-iron (atomic ratio 1∶9) oxyhydroxide

Mössbauer spectral (MS) and magnetic investigations on the products obtained by annealing coprecipitated La(III) and Fe(III) (atomic ratio 1∶9) oxyhydroxide gel to different temperatures in the range 100 to 1250°C are reported. The annealing temperatures were chosen on the basis of thermal analysis data. It is observed that the thermal behaviour of the bulk ferric gel is significantly influenced by La(III) incorporation. A quadrupole split doublet observed in the MS of the gel annealed from 100°C persists up to 570°C and for samples annealed from 850°C and above it is not discernable. However, a six-fingered hyperfine split pattern emerges even for the gel heated to 150°C indicating the onset of short-range ordering.H _n values ranging from 495 to 519 kOe for the samples heated to 570°C are in agreement with that for α-Fe₂O₃, however, their magnetic susceptibility per gram (χ_g) of the order of 10^?3 e.m.u. appears to be high for such systems. Annealing the gel from 850°C and above results in anH _n of about 526 kOe which is in better agreement with that of LaFeO₃, but the χ_g value falls to about 10^?5 e.m.u.     

Improvements in the performances of In–Ga–Zn–O thin-film transistors on glass substrates by annealing treatment

Thin film transistors (TFTs) with amorphous InGaZnO (IGZO) channel layer were fabricated by radio frequency magnetron sputtering technique. The IGZO films show optical transparency over 80 % both before annealing and after annealing. It was found that performances of transistors with IGZO thin films annealed in air at 450 °C were significantly improved. Through annealing treatment, Saturation current of TFTs increased from 2.8 to 181 μA at bias of V_DS = 20, V_GS = 20 V, and saturation mobility is up from 1.49 to 15.8 cm² V^?1 s^?1. In addition, X-ray photoelectric spectroscopy (XPS) was performed to provide elemental information on the surface of the IGZO films before and after annealing. O1s XPS spectra of unannealed and annealed IGZO films indicated oxygen vacancy concentration decreased by annealing treatment.     

Structural and optical properties of thermally evaporated zinc phthalocyanine thin films

Thermally evaporated zinc phthalocyanine (ZnPc) films in the as deposited condition were identified to be as-amorphous. It undergoes structural transformation upon annealing up to 613 K. The optical properties and spectral behavior of as deposited and annealed thin films of ZnPc were studied using spectrophotometric measurements of the transmissivity and reflectivity at normal incidence of light in the wavelength range 200–2500 nm. The refractive index, n, and absorption index, k, were calculated and it was found that they are independent of film thickness in the thickness range 205–530 nm. Annealing at 613 K increases absorbance of films by 5–6 times in comparison with absorbance of as deposited ones and shifts peak positions of all bands towards low energy side of spectra except the peak position of N-band is shifted towards high energy side of spectra. The absorption spectra in the UV–VIS. region has been analyzed in terms of both molecular orbital and band theories. Indirect allowed transitions near the onset and fundamental absorption edges were observed. The energy at the onset was obtained and equals to 1.45 and 1.51 eV for as deposited and annealed films, respectively. The fundamental energy gap was obtained and equals to 2.94 and 2.88 eV for as deposited and annealed films, respectively. The absorption spectra shows four absorption bands. The oscillator strength, f, the electric dipole strength, q², the molar extinction coefficient, ζ_molar, were calculated for as deposited and annealed ZnPc thin films.     

Effects of post-deposition annealing on the structure and optical properties of Y2O3 thin films

Y₂O₃ thin film waveguides were prepared by RF magnetron sputtering. The effects of post-deposition annealing on the structure and optical properties have been investigated. The structural evolution of Y₂O₃ films with annealing temperature was investigated by X-ray diffraction (XRD). Spectroscopic ellipsometry was employed to determine the optical properties of Y₂O₃ films annealed at various temperatures. It was found that with increasing annealing temperature, the refractive index (n) of Y₂O₃ films increases. The optical band gap of Y₂O₃ films shifts to higher energy after higher temperature annealing, which is likely due to the reduction of defects and the change of crystalline structure in Y₂O₃ films.     

Annealing effect on the structural,electrical and 1/f noise properties of Mn–Co–Ni–O thin films

Thin films of Mn_1.4Co_1.0Ni_0.6O₄ (MCN) spinel oxide are grown by radio frequency (RF) magnetron sputtering method on amorphous Al₂O₃ substrate. We investigate the annealing effect on the micro structural and electrical properties of RF sputtered MCN films. It is found that the crystallinity of MCN film is improved with increasing annealing time at 750 °C, and the annealed films present excellent cubic spinel (220) preferred orientation in X-ray diffraction patterns. Comparing to as-sputtered thin film, the annealed films show a decrease of 60 to 70 % in resistivity at 300 K. The annealed samples with post annealing time longer than 18 min acquire a negative temperature coefficient of resistance of about ?3.73 %K^?1 and resistivity of about 210–220 Ω cm at 300 K. 1/f noise of MCN films are also studied and the Hooge’s parameters (γ/n) are calculated. After annealing for 18 to 90 min, the γ/n values of the films are on the order of 10^?21 cm³, which ranks about two orders lower than that of amorphous silicon.     

Effect of annealing time on the structural,optical and electrical characteristics of DC sputtered ITO thin films

Using an Indium tin oxide (ITO) ceramic target (In₂O₃:SnO₂, 90:10 wt%), ITO thin films were deposited by conventional direct current magnetron sputtering technique onto glass substrates at room temperature. The obtained ITO films were annealed at 400 °C for different annealing times (1, 2, 5, 7, and 9 h). The effect of annealing time on their structural, optical and electrical properties was investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), atomic force microcopy (AFM), ultra violet–visible (UV–Vis) spectrometer, and temperature dependence Hall measurements. XRD data of obtained ITO films reveal that the films were polycrystalline with cubic structure and exhibit (222), (400) and (440) crystallographic planes of In₂O₃. AFM and Scanning Electron Microscopy SEM have been used to probe the surface roughness and the morphology of the films. The refractive index (n), thickness and porosity (%) of the films were evaluated from transmittance spectra obtained in the range 350–700 nm by UV–Vis. The optical band gap of ITO film was found to be varying from 3.35 to 3.47 eV with the annealing time. The annealing time dependence of resistivity, carrier concentration, carrier mobility, sheet resistance, and figure of merit values of the films at room temperature were discussed. The carrier concentration of the films increased from 1.21 × 10²⁰ to 1.90 × 10²⁰ cm^?3, the Hall mobility increased from 11.38 to 18 cm² V^?1 s^?1 and electrical resistivity decreased from 3.97 × 10^?3 to 2.13 × 10^?3 Ω cm with the increase of annealing time from 1 to 9 h. Additionally, the temperature dependence of the carrier concentration, and carrier mobility for the as-deposited and 400 °C annealed ITO films for 2 and 9 h were analysed in the temperature range of 80–350 K.     

Surface morphology and thermal figure of merit of a new compound thin film

The third nonlinear optical properties of a new compound 4,4′-bis(3-methoxy benzylidene amino) biphenyl doped poly-methyl methacrylate (PMMA) have been studied using Z-scan technique. Experiments are performed using a continuous waveguide (cw) diode laser at 532 nm wavelength and 0.68 kW/cm² laser intensity. The optical power limiting behavior of sample doped PMMA was also investigated. It also shows a very good optical limiting behavior with a limiting threshold of 4.7 mW. We attribute the nonlinear absorption and optical limiting property of the sample film to two photon absorption effect at 532 nm. The experimental evidences of observing diffraction pattern in compound 4,4′-bis(3-methoxybenzylideneamino) biphenyl doped PMMA has been present. The refractive index change, Δn, and nonlinear refractive index, n ₂ determined from the number of observed ring. We obtained good values of Δn = 105.154 × 10^?4and n ₂ = 154.154 × 10^?7 cm²/W. Variation of refractive index with temperature, dn/dT, and figure of merit, H, are found to be 8.858 × 10^?6 1/°C and 5.316 × 10^?6, respectively. This large nonlinearity is attributed to a thermal effect resulting from linear absorption. Theoretical diffraction pattern that agree well with experimental one are generated using a wave theory.     

Effect of pre-deposition annealing on physical properties of CZTSSe thin films deposed by RF-sputtering based on nanoparticles synthesized by solvothermal technique

This work aims to highlight the beneficial effect of annealing of Cu₂ZnSn(S,Se)₄ (CZTSSe) nanoparticles (NPs) on the properties of the obtained films by RF-magnetron sputtering at room temperature (RT) and at 200 °C. The CZTSSe targets used for the deposition are obtained using nanoparticles synthesized by solvothermal technique. It is denoted that the elemental composition of thin films becomes independent of the growth temperature in the case of annealed CZTSSe NPs. The optical investigation gives that the gap energy is ranging between 1.26 and 1.40 eV with an Urbach’s energy between 100 and 200 meV. By using the Wemple and Didominico model to analyze the refractive index spectra, we have identified common oscillator energy for all CZTSSe thin films and dispersion energy ranging from 2.63 to 5.81 eV. CZTSSe thin films obtained by means of annealed NPs exhibit higher dielectric constant and refractive index. The dispersion of different parameters with experimental conditions is analyzed via a common relationship that illustrates the linear dependence of n₀, E_d, ε_s, and ε_L on the square of the valence difference (ΔZ). The conductivity spectra are deduced, and a theoretical model was identified to fit the permittivity spectra. The obtained results are promising for solar cell applications.

     

Tensile mechanical behaviour of quenched and annealed isotactic polypropylene films over a wide range of strain rates

The tensile mechanical behaviour of quenched and annealed isotactic polypropylene (iPP) films has been analysed over a wide range of strain rates, i.e. from 10^–3 to 3×10⁺²s^–1. Evolution of mechanical properties of such films versus strain rate has been analysed through the microstructure. Thus, both the Young's modulus and the yield stress could be mainly controlled not only by the crystallinity ratio but also by the physical cross-linking degree of the amorphous phase induced by crystalline entities. For a given crystallinity ratio, the drawability of quenched and annealed iPP films is mainly controlled by the sum of the effects induced by both the physical cross-linking degree of the amorphous phase and the perfection degree of the crystalline phase. The increase in annealing temperature leads to the opposite evolution of these two microstructural parameters and then to opposite effects on the drawability of films. Changes in original microstructure of quenched films induced by drawing at various draw ratios and at various strain rates are also discussed.     

Crystal structure and optical absorption investigations on β-In2S3 thin films

The crystal structure of annealed β-In₂S₃ thin films with different thickness was investigated by X-ray diffraction technique. Lattice parameters, crystallite size and microstrain were calculated. It was found that the lattice parameters are independent on film thickness, while annealing temperatures increase them. Crystallite sizes were increased with the increase of the film thickness and improved by annealing temperatures. In all cases, the microstrains were decreased gradually with the increase in both film thickness and annealing temperatures. Optical properties of β-In₂S₃ thin films were performed in the spectral range from 400 to 2500 nm to determine the optical constants (n and k), the high frequency dielectric constant, ε_∞, the lattice dielectric constant, ε_L, and the energy gap. The optical constants were found to be independent on film thickness in the range from 200 to 630 nm. The high frequency dielectric and lattice dielectric constants of the as-deposited film increased by annealing temperatures. The energy gap for the as-deposited In₂S₃ was found to be 2.60 eV and increased to 2.70 and 2.75 eV by annealing at 423 and 473 K for 1 h, respectively.     

Enhanced photocatalytic activity of Mg0.05Zn0.95O thin films prepared by sol–gel method through a cycle

Mg_0.05Zn_0.95O thin films were prepared on silicon substrates by a sol–gel dip-coating technique. Microstructure, surface topography and optical properties of the thin films were characterized by X-ray diffraction, atom force microscopy, Fourier transform infrared spectrophotometer and fluorescence spectrometer. The results show that the thin film annealed at 700 °C has the largest average grain size and exhibits the best c-axis preferred orientation. As annealing temperature increases to 800 °C, the grain along c-axis has been suppressed. Roughness factor and average particle size increase with the increase of annealing temperature. The IR absorption peak appearing at about 416 cm^?1 is assigned to hexagonal wurtzite ZnO. The thin film annealed at 700 °C has the maximum oxygen vacancy, which can be inferred from the green emission intensity. Photocatalytic results show that the thin film annealed at 700 °C exhibits remarkable photocatalytic activity, which may be attributed to the larger grain size, roughness factor and concentration of oxygen vacancy. Enhanced photocatalytic activity of Mg_0.05Zn_0.95O thin films after a cycle may be attributed to the increase of surface oxygen vacancy and photocorrosion of amorphous MgO on the surface of thin film under UV irradiation.     

Annealing dependence of optical properties of Ga20S75Sb5 and Ga20S40Sb40 thin films

Amorphous Ga₂₀S₇₅Sb₅ and Ga₂₀S₄₀Sb₄₀ thin films were prepared onto glass substrates by using thermal evaporation method. The effect of annealing (under vacuum) at different temperatures on the optical parameters was investigated in the temperature range 373-593 K. The optical absorption coefficient (α) for the as-deposited and annealed films were calculated from the reflectance and transmittance measurements in the range 190-900 nm. X-Ray diffraction indicates that the as-deposited films and those annealed up to the glass transition temperature (T_g) exhibit amorphous state. On annealing above the glass transition temperature these films show a polycrystalline structure. Analysis of the optical absorption data indicates that the optical band gap E_g^opt of these films obeys Tauc's relation for the allowed non-direct transition. It was found that the optical band gap E_g^opt increases with annealing temperature up to T_g, whereas above T_g there is a remarkable decrease. The obtained results were interpreted on the basis of amorphous- crystalline transformation.     

Synthesis of SiOF nanoporous ultra low-k thin film

In this work, we have investigated the effect of annealing temperature on physical, chemical and electrical properties of Fluorine (F) incorporated porous SiO₂ xerogel low-k films. The SiO₂ xerogel thin films were prepared by sol–gel spin-on method using tetraethylorthosilicate as a source of Si. The hydrofluoric acid was used as a catalyst for the incorporation of F ion in the film matrix. The thickness and refractive index (RI) of the films were observed to be decreasing with increase in annealing temperature with minimum value 156 nm and 1.31 respectively for film annealed at 400 °C. Based on measured RI value, the 34 % porosity and 1.53 gm/cm³ density of the film annealed at 400 °C have been determined. The roughness of the films as a function of annealing temperature measured through AFM was found to be increased from 0.9 to 1.95 nm. The Electrical properties such as dielectric constant and leakage current density were evaluated with capacitance–voltage (C–V) and leakage current density–voltage (J–V) measurements of fabricated Al/SiO₂ xerogel/P–Si metal–insulator-semiconductor (MIS) structure. Film annealed at 400 °C, was observed to be with the lowest dielectric constant value (k = 2) and with the lowest leakage current (3.4 × 10^?8 A/cm²) with high dielectric breakdown.