Effects of morphology on NO2 detection in air at room temperature with phthalocyanine thin films

Lead phthalocyanine films freshly deposited on alumina and glass were found to consist of disordered phases and fine particles with mean diameter below 0.2m. Following annealing at 300 ° C, a transition to a crystalline form is obtained. The crystal size in the films annealed at 300 ° C or above is affected by the nature of the substrate, ambient atmosphere and annealing time. Following an optimized preparation procedure, the films exhibit response times of less than 20 sec and recovery times of the order of several minutes, independently of N0₂ concentration or exposure time, at room temperature. They consist of fine crystals with mean diameters of the order of 0.2m and amorphous phases are not observed. For zinc, copper, cobalt and nickel phthalocyanine films, some improvements in the response and recovery times are achieved by annealing but not sufficient to allow No₂ detection at room temperature. For films of these phthalocyanines, fine crystals of the type formed in leadphthalocyanine films were not produced in the conductive paths when the films were annealed at 300 ° C in air.     

Electrical and optical properties of annealed gallium arsenide thin films on glass substrates

The effects of annealing in vacuum on the electrical and optical properties of GaAs thin films deposited by the flash evaporation method were studied. Thin films of compound GaAs deposited upon glass substrates at room temperature were annealed in a vacuum of 2×10^–6 torr at different temperatures up to 350° C. The properties of the films depended strongly on annealing temperature. The lowest resistivity measured was about 1.6 × 10⁴ cm at an annealing temperature of about 240° C. The activation energy of as-deposited and annealed films were measured and compared. Optical absorption measurements of the asdeposited samples and the samples annealed at a temperature of 240° C were made as a function of photon energy.     

Electrical properties of non c-axis oriented SrBi2(Ta0.95V0.05)2O9 thin films

Pulsed laser deposition technique was used to grow off c-axis oriented SrBi₂(Ta_0.95V_0.05)₂O₉ (SBTV) ferroelectric thin films. X-ray diffraction studies revealed the c-axis suppression in the films grown at lower substrate temperature (350°C) followed by annealing at higher temperatures (650°C). In-plane lattice parameters of the films were decreased with increase in annealing temperature. SBTV films annealed at 750°C exhibited enhanced ferroelectric properties with remanent polarization (2P _r) of 31.5 C/cm² and coercive field (E _c) of 157 kV/cm. The dielectric permmitivity of the films increased with increase in annealing temperature and it was attributed to the grain size dependence. The films annealed at 750°C showed maximum value of dielectric permittivity 172 with a tangential loss of 0.1, at 100 kHz. Higher value of dissipation factor at lower annealing temperature is explained in terms of space charge accumulation at grain boundaries. The leakage current densities of the films follow ohmic behavior at low field regime and space charge limited current dominates at higher fields.     

Characterization of lead zirconate titanate thin film deposition onto Pt/Ti/SiO2/Si substrates

Lead zirconate titanate, (Pb(Zr_0.52Ti_0.48)O₃PZT) thin films were deposited onto a Pt/Ti/SiO_2/Si substrate using radio frequency (r.f.) planar magnetron sputtering in this study. The deposited PZT thin films were almost amorphous before the annealing processes and developed a perovskite structure after the annealing process. If the annealing temperature was too low or annealing time too short, pyrochlore would form. However, if the annealing temperature was too high or annealing time too long, the thin film structure would degrade due to the volatilization of PbO. The significant finding in this experiment is that high quality perovskite PZT thin films on Pt/Ti/SiO_2/Si substrates can be obtained by adjusting the annealing temperature to a range of 650 °C to 850 °C and annealing time to a range from 5 to 80 min. In this experiment, the optimal annealing condition was an annealing temperature of 650 °C and time of 20 min. The properties of PZT thin film annealed at 650 °C for 20 min were dielectric constant _r = 869 free dielectric constant ^T ₃₃ = 893 piezoelectric constant d₃₃ = 2.03p m V^-1 piezoelectric constant g₃₃ = 2.57 x 10^-4 V m N^-1, remanent polarization P₁ = 112.5 nC cm^-2 and coercive field E_c= 0.061 kV cm^-1.     

Degradation of thin films of YBa2Cu3O7 by annealing in air and in vacuum

The degradation of epitaxial thin films of YBa₂Cu₃O₇ has been studied as a function of annealing temperature in air and in vacuum; some samples had an evaporated overlayer of CaF₂. Degradation was monitored by the measurement of electrical properties after consecutive 30-min annealing treatments. The room-temperature resistance registered significant increases for all samples after annealing at temperatures above about 200°C; the critical current density at 77 K was degraded for annealing temperatures 400°C in air, and 200–250°C in vacuum. By annealing in oxygen at 550°C, electrical properties were restored in degraded bare YBCO samples annealed in vacuum, but not for those annealed in air.     

Preparation of PbTiO3 thin films using an alkoxide-alkanolamine sol-gel system

The stable range of PbTiO₃ sol and the processing conditions of uniform thin films were investigated using a solution of titanium isopropoxide, three kinds of alkanolamines (monoethanolamine, diethanolamine, triethanolamine), lead acetate trihydrate and isopropanol. Depending on the sol state with various alkanolamine/alkoxide molar ratios, diethanolamine (DEA) was very effective in preparing uniform and dense oxide films through room-temperature reaction, owing to its superior stability during the hydrolysis and condensation reaction. Perovskite PbTiO₃ thin films were obtained on oxidized silicon wafer above 550 °C and completely pure films were obtained at 650 °C using DEA as a complexing agent. The dielectric constant and loss tangent of these thin films fired at 650 °C for 30 min were found to be 240 and 0.01 at 1 kHz, respectively.     

Structural and optical properties of n-propoxide sol-gel derived ZrO2 thin films

In this work, we present a sol-gel method for the preparation of zirconia films. Using zirconium n-propoxide as the starting precursor, a ZrO₂ sol has been synthesized that remains stable for several months. Thin films were deposited using the dip-coating method. The structural characterization was performed using waveguide Raman spectroscopy. The films present an amorphous phase up to an annealing temperature of 400 °C. Both monoclinic and tetragonal phases were obtained for annealing temperatures higher than 450 °C. The proportions of these two phases were calculated from the Raman spectra and the size of the crystallites was evaluated using the low-wavenumber Raman band. The optical properties were characterized by the m-lines technique (n = 1.96) and UV-visible spectroscopy. The optical losses for a TE₀ mode were measured to be 0.29 ± 0.03 dB cm^− 1 for a sample annealed at 400 °C. To optimize the protocol for thermal annealing, a powder obtained from a dried sol was characterized by Thermal Gravimetric Analysis. Rutherford Back Scattering was employed to determine the chemical composition and the stoichiometry of the zirconia films.     

Optical and structural properties of (Ba, Sr)TiO3 thin films grown by radio-frequency magnetron sputtering

We studied the structural and optical properties of (Ba, Sr)TiO₃ (BST) films deposited on the transparent substrates at various temperatures of 350–650°C and annealed at 450–650°C. Improved crystallization can be observed on 650°C annealed film whose substrate temperature is 350°C. The refractive index increased from 2.17 to 2.59 at =410 nm for the BST films deposited at 350–650°C and it varied from 2.17 to 2.25 after annealing up to 650°C. In addition, the refractive-index dispersion data related to the short-range-order structure of BST films obeyed the single-oscillation energy model. The indirect energy gap of the films deposited on Al₂O₃ and quartz substrates was found to be about 3.5 eV. According to the analysis of reflectance data, the optical inhomogeneity of films can be reduced by depositing the films at intermediate temperatures 450–550°C.     

Influence of annealing on properties and structure of alumina

Alumina bodies were prepared from pure alumina powder (98.9% Al₂O₃ consisting of 82% > 53m). The powder was compacted by hot-pressing at 1200° C, Compacted bodies were annealed at 1300, 1400 and 1500° C. Annealing continued at each maximum temperature for 25, 50 and 100 h. Strong bodies were obtained with maximum bulk density of 2.32 g cm^–3 and minimum apparent porosity of 30.21%. The change in sintering parameters with annealing was correlated with developed structure.     

Preparation of fatigue-free SrBi2Ta2O9 thin films by r.f. magnetron sputtering and their ferroelectric properties

Fatigue-free bismuth-layered SrBi₂Ta₂O₉ (SBT) films were deposited on Pt/Ti/SiO₂/Si substrates by r.f. magnetron sputtering at room temperature. The variation of structure and electrical properties were studied as a function of annealing temperatures from 750–850 °C. The films annealed at 800 °C had a composition ratio of Sr:Br:Ta = 0.7:2.0:2.0. X-ray photoelectron spectroscopy signals of bismuth show an oxygen-deficient state within the SBT films. The films annealed at 800 °C have a thickness of 200 nm and a relatively dense microstructure. The remanent polarization (2P _r), and the coercive field (2E _c), obtained for the SIBT films, were 9.1 C cm^–2 and 85 kV cm^–1 at an applied voltage of 3 V, respectively. The films showed fatigue-free characteristics up to 10¹⁰ cycles under 5 V bipolar square pulses. The leakage current density was about 7 × 10^–7 A cm^–2 at 150 kV cm^–1. The SBT films prepared by r.f. magnetron sputtering were attractive for application to non-volatile memories.     

Influence of annealing on humidity response of RF sputtered nanocrystalline MgFe2O4 thin films

Humidity response of Radio Frequency sputtered MgFe₂O₄ thin films onto alumina substrate, annealed at 400 °C, 600 °C and 800 °C has been investigated. Crystalline phase formation of thin films annealed at different temperature was analyzed by X-ray Diffraction. A particle/grain like microstructure in the grown thin films was observed by Scanning Electron Microscope and Atomic Force Microscope images. Film thickness for different samples was measured in the range 820-830 nm by stylus profiler. Log R (Ω) response measurement was taken for all thin films for 10-90% relative humidity (% RH) change at 25 °C. Resistance of the film increased from 5.9 × 10¹⁰ to 3 × 10¹² at 10% RH with increase in annealing temperature from 400 °C to 800 °C. A three-order magnitude, 10¹² Ω to 10⁹ Ω drop in resistance was observed for the change of 10 to 90% RH for 800 °C annealed thin film. A good linear humidity response, negligible humidity hysteresis and minimum response/recovery time of 4 s/6 s have been measured for 800 °C annealed thin film.     

Effect of annealing on the composition, structure and mechanical properties of carbon nitride films deposited by middle-frequency magnetron sputtering

Carbon nitride films were deposited by middle-frequency reactive magnetron sputtering and annealed at different temperatures in nitrogen ambient. X-ray photoelectron spectroscopy, Raman scattering, transmission electron microscopy, and nano-indenter were used to characterize the as-deposited and annealed films. The analysis showed that annealing resulted in the dissociation of N and C in the films. The dissociation of C happened after 500 °C and lagged behind that of N. With the increase of annealing temperature, the disorder of sp² C decreased and the films were gradually graphitized. The microstructure changed from amorphous to fullerene-like CN_x with the annealing temperature increasing to 500 °C, and then to nitridized graphite nanocrystals at 600 °C. The graphitization resulted in a drastic decreasing of hardness and modulus of the films.     

Structural and optical characterization of CuInS2 thin films grown by vacuum evaporation method

Structural and optical properties of CuInS₂ thin films grown by the single-source thermal evaporation method have been studied. The films were annealed from 100 to 500 °C after an evaporation in air. The surface morphology was investigated by scanning electron microscopy. The maximum grain size of the samples after annealing at 400 °C was over 500 nm. The EPM analysis concluded that the polycrystalline CuInS₂ thin films after annealing below 100 °C were Cu-rich, and those annealed above 200 °C were In-rich. The bandgap energy of the CuInS₂ films after annealing above 300 °C was about 1.48 eV.     

Growth and vacuum post-annealing effect on the properties of the new absorber CuSbS2 thin films

Post-growth treatments in vacuum atmosphere were performed on CuSbS₂ films prepared by the single-source thermal evaporation method on glass substrates. The films were annealed in vacuum atmosphere for 2 h in temperature range 130-200 °C. The effect of this thermal treatment on the structural, optical and electrical properties of the films was studied. X-ray diffraction (XRD) patterns indicated that the films exhibited an amorphous structure for annealing temperature below 200 °C and a polycrystalline structure with CuSbS₂ principal phase. For the films annealed at temperatures below 200 °C one direct optical transition in range 1.8-2 eV was found. For the films annealed at 200 °C, two optical direct transitions emerged at 1.3 and 1.79 eV corresponding to the CuSbS₂ and Sb₂S₃ values respectively. The electrical measurements showed a conversion from low resistivities (3.10^− 2-9.10^− 2) Ω cm for the samples annealed at temperatures below 200 °C to relatively high resistivities (2 Ω cm) for the samples annealed at 200 °C. In all cases the samples exhibited p-Ztype conductivity.     

Characterization and optoelectronic properties of sol-gel-derived CuFeO2 thin films

In this study, CuFeO₂ thin films were deposited onto quartz substrates using a sol-gel and a two-step annealing process. The sol-gel-derived films were annealed at 500 °C for 1 h in air and then annealed at 600 to 800 °C for 2 h in N₂. X-ray diffraction patterns showed that the annealed sol-gel-derived films were CuO and CuFe₂O₄ phases in air annealing. When the films were annealed at 600 °C in N₂, an additional CuFeO₂ phase was detected. As the annealing temperature increased above 650 °C in N₂, a single CuFeO₂ phase was obtained. The binding energies of Cu-2p_3/2, Fe-2p_3/2, and O-1s were 932.5 ± 0.1 eV, 710.3 ± 0.2 eV and 530.0 ± 0.1 eV for CuFeO₂ thin films. The chemical composition of CuFeO₂ thin films was close to its stoichiometry, which was determined by X-ray photoelectron spectroscopy. Thermodynamic calculations can explain the formation of the CuFeO₂ phase in this study. The optical bandgap of the CuFeO₂ thin films was 3.05 eV, which is invariant with the annealing temperature in N₂. The p-type characteristics of CuFeO₂ thin films were confirmed by positive Hall coefficients and Seebeck coefficients. The electrical conductivities of CuFeO₂ thin films were 0.28 S cm^− 1 and 0.36 S cm^− 1 during annealing at 650 °C and 700 °C, respectively, in N₂. The corresponding carrier concentrations were 1.2 × 10¹⁸ cm^− 3 (650 °C) and 5.3 × 10¹⁸ cm^− 3 (700 °C). The activation energies for hole conduction were 140 meV (650 °C) and 110 meV (700 °C). These results demonstrate that sol-gel processing is a feasible preparation method for delafossite CuFeO₂ thin films.     

Properties of indium oxide/tin oxide multilayered films prepared by ion-beam sputtering

The preparation and characterization of indium oxide (InO _x )/tin oxide (SnO _y ) multilayered films deposited by ion-beam sputtering are described and compared with indium tin oxide (ITO) films. The structure and the optoelectrical properties of the films are studied in relation to the layered structures and the post-deposition annealing. Low-angle X-ray diffraction analysis showed that most films retained the regular layered structures even after annealing at 500° C for 16 h. As an example, we obtained a resistivity of 6×10^–4 cm and a transparency of about 85% in the visible range at a thickness of 110 nm in a multilayered film of InO _x (2.0 nm)/SnO _y (0.2 nm)×50 pairs when annealed at 300° C for 0.5 h in air. Hall coefficient measurements showed that this film had a mobility of 17 cm² V^–1 sec^–1 and a carrier concentration (electron density) of 5×10²⁰ cm^–3.     

Characterization of (Pb,La) TiO3 thin films prepared by the sol-gel method

Pb_(1–1.5x)La_xTiO₃ thin films were synthesized by the sol-gel spin-coating technique. The films became crystallized when the spin-coated films were annealed at 600 °C and at higher temperature, and became amorphous when annealed at 550 °C. The breakdown voltage, V _B, was recorded at around 30 V for 600–650 °C annealed films and varied only slightly with the composition. The V _B value of the amorphous films was observed to be higher than that of the crystalline films. The ferroelectric properties of both the amorphous and crystalline films were found to be similar. The dielectric constant, charge storage density and optical index of refraction of the films were _r =5–20, Q _c=0.12–0.54 C cm^–2 and n=1.6–2.3, respectively. They all increased moderately with La³⁺ content in the films. One possible reason why the ferroelectric properties are not modified as the amorphous films crystallize, may be that the octahedra are equilateral, whether the films are amorphous or crystalline. Additionally, a possible cause which lowers the breakdown voltage in crystalline film, is the formation of lead vacancies due to lead loss. The electrical properties of films coated on bare silicon become significantly lowered due to interdiffusion between films and substrate. The diffusion of Si⁴⁺ ions into-the films can be prevented by coating SrTiO₃ on the silicon substrate as a buffer layer. The charge storage capacity consequently becomes substantially enhanced.     

Structural and optical properties of Er-doped Y2Ti2O7 thin films by sol-gel method

Er³⁺-doped Y₂Ti₂O₇ and Er₂Ti₂O₇ thin films were fabricated by sol-gel spin-coating method. A well-defined pyrochlore phase Er_xY_2-xTi₂O₇ was observed while the annealing temperature exceeded 800 °C. The average transmittance of the Er_xY_2-xTi₂O₇ thin films annealed at 400 to 900 °C reduces from ∼ 87 to ∼ 77%. The refractive indices and optical band gaps of Er_xY_2-xTi₂O₇ (x = 0-2) annealed at 800 °C/1 h vary from 2.20 to 2.09 and 4.11 to 4.07 eV, respectively. The ∼ 1.53 μm photoluminescence spectrum of Er³⁺ (5 mol%)-doped Y₂Ti₂O₇ thin films annealed at 700 °C/1 h exhibits the maximum intensity and full-width at half maximum (∼ 60 nm).     

Structural behaviour of sputtered W-C-Co coatings at increasing temperatures

In order to evaluate the thermal resistance of sputtered W-C-Co coatings, a structural study was carried out on amorphous and crystalline coatings according to their cobalt content after having been annealed at increasing temperatures up to 800 °C. All the films were stable up to 700°C, at which temperature the amorphous films began to crystallize as -W₂C; for higher temperatures the -W₂C carbide evolves to M₆C, the extent of which increases the higher the cobalt content; for low cobalt content films WC carbide was also formed. Crystalline films have similar structural transformations, although the M₆C phase is almost non-existent and -W₂C and WC can occur with preferential orientations. In all cases, the films after annealing were carbon-deficient in relation to the results obtained for the as-deposited conditions; in spite of the fact that the phases detected after crystallization are also carbon-deficient, these results are not consistent which implies that some free carbon should exist in the annealed films.