Formation of porous calcium phosphate films on partially stabilized zirconia substrates by the spray-pyrolysis technique

Porous calcium phosphate films could be formed on partially stabilized zirconia (3YZ) substrates by a spray-pyrolysis technique. The use of calcium metaphosphate as a binder was effective to enhance the binding strengths of these films to the substrates. The crystalline phase in the resulting films was mainly -calcium orthophosphate. This phase was thermally stabilized by solid solution with Y³⁺. The thickness of the film (30–150 m) was dependent upon the spraying time; the pore size was about 15 m. The films were still present on the substrate after Scotch tape (810) was adhered to the film side and then taken off from the substrate. The films prepared in this study were found to bind strongly to the substrate.     

Preferred growth of epitaxial TiN thin film on silicon substrate by pulsed laser deposition

Epitaxial TiN thin films on silicon substrates were prepared by pulsed excimer laser (KrF, 34 ns) ablation of a hot-pressed TiN target in nitrogen gas atmosphere. X-ray diffraction (XRD) showed that the preferred orientations of TiN thin films did not change with substrate temperatures, nitrogen gas pressure and film thickness; however, they did change with the orientations of substrates. The epitaxial orientation relationships between high-quality epitaxial TiN thin films and silicon substrates [2 4 2] TiN [2 4 2] Si, (1 1 1) TiN(1 1 1) Si and [3 1 1] TiN [3 1 1] Si, (1 0 0) TiN(1 0 0) Si. The full-width at half-maximum (FWHM) of the rocking curve of XRD and the minimum channelling yield of Rutherford backscattered spectroscopy (RBS) of the epitaxial TiN thin film were estimated to be 0.3 ° and 7.3%, respectively, indicating excellent crystalline quality of the grown film. X-ray photoelectron spectroscopy confirmed that the binding energies of Ti 2p 3/2 and N 1s core levels in epitaxial thin film were 455.2 and 397.1 eV, respectively, corresponding to those of TiN bulk. By calibrating the RBS spectra, the chemical composition of TiN thin films was found to be titanium-rich. The typical surface roughness of TiN thin film observed by scanning probe microscopy was about 1.5 nm. © 1998 Chapman & Hall     

Effect of thermal annealing on transparent conductive LaNiO3 thin film prepared by an aqueous method

Dense, crack-free and uniform lanthanum nickel oxide (LNO) thin films were prepared by an aqueous method on various substrates, such as single crystal silicon, microcrystalline glass ceramic (GC) and amorphous glass. The effects of various thermal annealing temperatures on the microstructure, interface and electrical properties of the LNO films were investigated by XRD and SEM with the EDX and a four-probe method, respectively. It was found that with the increase in thermal annealing temperature, the LNO film on Si substrates displayed a structure change from pseudocubic to rhombohedral and was accompanied by the appearance of a NiO impure phase, while the LNO film on a GC substrate diffused into the substrate. In these cases, the film resistivity was increased. As a result, a LNO thin film with a resistivity of 2–3 × 10^–5 · m was achieved by thermally annealing at 750–800°C for 1 hour in air. The measurement of the surface resistance under different temperatures shows that the LNO film possesses better high temperature stability. Its transmittance spectrum was also observed.     

An etch rate study on thermally annealed SiO2 films deposited in a TEOS-LPCVD system

The etch rate behaviour of tetraethylorthosilicate (TEOS)-SiO₂ films was investigated as a function of annealing parameters (time, temperature and ambient pressure). The etch rate of TEOS-SiO₂ films depends strongly on annealing pressure within the temperature range 750 to 900 C, while the etch-rate behaviour of films thermally annealed at 1000 C is mainly controlled by the thermally activated rearrangements of SiO₄ tetrahedra from as-deposited films in a closed structure to that of thermally grown SiO₂ films. The etch-rate behaviour of thermally annealed TEOS-SiO₂ films is interpreted in terms of the chemical change of the film structure.     

High-Temperature Zinc Doping of Silicon from Zinc-Containing SiO2 Films

Experimental evidence is presented that high-temperature annealing of Zn-containing SiO₂ films on Si gives rise to phase separation, accompanied by the formation of Zn-enriched bands. Appreciable amounts of zinc (sufficient to change the conductivity type of Si and to raise its resistivity) diffuse to only small depths (10 m) and at relatively short diffusion times. Long-term high-temperature annealing reduces the Zn concentration in the film. This process can be inhibited by applying a protective SiO₂ layer.     

Effect of binders on microstructure and photoelectrochemical properties of the TiO2 film photoelectrodes

In order to obtain thick, crack-free TiO₂ film photoelectrodes, the screen-printed method was employed by using ethylene glycol and ethylene glycol monomethylether (EGME) as binder. The surface morphology of TiO₂ film observed by scanning electron microscope (SEM) is porous and coarse. SEM results also show that TiO₂ films with binder are crack-free in the microstructure. Optical absorption spectra show that films with binder have stronger ability to adsorb dye molecules than that without binder. I–V curves show that films with binder have better photoelectrochemical (PEC) property than films without binder. Moreover, EGME improves the PEC property of the sample stronger than ethylene glycol.     

Piezoelectric paints: preparation and application as built-in vibration sensors of structural materials

Piezoelectric paints were prepared using lead zirconate titanate (PZT) ceramic powder as a pigment and epoxy resin as a binder. The obtained paints were spread on the surface of an aluminium beam and cured at room temperature, thus forming the final thin films having thicknesses of 35–81 m and PZT volume fractions of 25%–53%. The thin films were then poled under electric fields of up to 350 kV cm^–1 at room temperature, and the resulting piezoelectric activity was evaluated from vibration measurements on the aluminium beam. Although not strictly quantitative, the piezoelectric activity of the thin film showed a tendency to increase with an increase in the film thickness and the PZT volume fraction. From the standpoint of the thin film application as built-in vibration sensors, the piezoelectric activity was confirmed to be high enough to determine the natural frequencies and mode shapes of the aluminium beam.     

Development of phases and texture in sol-gel derived lead zirconate titanate thin films prepared by three-step heat-treatment process

Lead zirconate titanate (PZT) films were fabricated by the addition of 10 mol% excess Pb to the starting solution which was spin-coated onto Pt/Ti/SiO₂/Si substrates. The effect of film thickness on texture was investigated, and it is clear that the (100) texture gradually increases and the (111) texture decreases with increasing film thickness. A Pt _x Pb intermetallic metastable phase was observed by X-ray diffraction, and it is found that the position of this peak shifted from 38.30° 2 (d : 0.2348 nm) to 37.10° 2 (d : 0.4213 nm) with increasing firing temperature from 350°C to 550°C. The (111) preferred orientation in the PZT film was promoted by the metastable Pt _x Pb phase. The formation of the (100) texture of perovskite phase in the multilayer films was mainly attributed to the effects of both substrates and crystal growth rates which depend on the crystal orientation.     

Spectroellipsometric studies of 0.9PbMg1/3Nb2/3O3-0.1PbTiO3 thin films

0.9PbMg_1/3Nb_2/3O₃-0.1PbTiO₃ (PMN-PT) films of different thickness, ranging from 75 to 450 nm, were prepared on La_0.5Sr_0.5MnO₃ (LSMO)-buffered LaAlO₃ (LAO) substrates by pulsed laser deposition (PLD). The structural properties of these films were characterized by X-ray diffraction. The –2 scans indicated that all the films have a pure perovskite phase containing no impurity. The - and -scans confirmed that all the films possess a heteroepitaxial relation of PMN-PT(1 0 0) LSMO(1 0 0) LAO(1 0 0) structure. The surface morphology and cross section of the films were examined by scanning electron microscopy (SEM). Their dielectric constants and the leakage currents were measured by an impedance analyzer and a leakage digital electrometer, respectively. Furthermore, spectroellipsometry (SE) was used to characterize the depth profile, refractive index, and microstructural inhomogeneities, including voids, microroughness of surface, and the electrode/film interface of these films. Based on these studies, the correlation between the electrode/film interface and the electrical properties of the films was discussed. Our results show that the ratio of the electrode/film interface thickness to the film thickness increases as the film thickness decreases. The increase in this ratio results in deterioration of the leakage current and dielectric constant of the films.     

Low-voltage characteristics of MgO-CaO films as a protective layer for AC plasma display panels by e-beam evaporation

The MgO-CaO composites films were prepared by e-beam evaporation to improve both operating voltages and memory coefficient of a protective layers for AC plasma display panels (PDPs). The effects of CaO addition to the conventional MgO films on both the electrical properties and the structural changes of the Mg_1–xCa_xO thin films deposited on the slide glass substrates were investigated. Atomic force microscopy (AFM) results revealed that the Mg_0.8Ca_0.2O film had a very rough surface due to the formation of a second phase on the surface. By adding controlled amount of CaO, the Mg-Ca-O films showed a firing voltage of 176 V that is lower than that of the conventional 100% MgO film. The deposition rates of 40–100 nm/min were obtained as a function of [CaO/(MgO+CaO)] ratio of the evaporation source materials.     

Thickness dependence of H2 gas sensor in amorphous SnQx films prepared by ion-beam sputtering

Amorphous SnO_x films were deposited by ion-beam sputtering on sintered alumina substrates. Amorphous film sensors were prepared by annealing the films at 300° C for 2 h in air. The thickness dependence of resistivity and hydrogen gas sensitivity were measured at 150° C over the thickness range 1 to 700 nm. A resistivity maximum was observed in ultrathin films. Resistivity increased by three orders of magnitude with increasing film thickness from 0.9 to 7.4 nm and then decreased by five orders of magnitude from 7.4 to 35 nm. Ultrathin film sensors showed sensitivity maxima around a thickness of 10 nm. Sensitivity and resistivity of ultrathin films were significantly influenced by the thermal expansion coefficient and the surface state of the substrate.     

Artificial Pinning Centers on MgB2 Superconducting Thin Films Coated by FeO Nanoparticles

MgB₂ thin films were fabricated on MgO (100) single crystal substrates. First, deposition of boron was performed by rf magnetron sputtering on MgO substrates and followed by a post deposition annealing at 850?°C in magnesium vapor. In order to investigate the effect of FeO nanoparticles on magnetic properties of MgB₂ thin films, the films were coated with different concentrations of FeO nanoparticles by spin coating process. The magnetic field dependence of the critical current density $J_{\mathrm{c}}$ was calculated from the M?CH loops and also magnetic field dependence of the pinning force density $f_{\mathrm{p}}(b)$ was determined for the films containing different concentrations of FeO nanoparticles. The values of the critical current density $J_{\mathrm{c}}$ in zero field at 5?K was found to be around 1×10⁶?A/cm² for pure MgB₂ film, 1.4×10⁶ for MgB₂ film coated with 25?%, 7.2×10⁵ for MgB₂ film coated with 33?%, 9.1×10⁵ for MgB₂ film coated with 50?% and 1.1×10⁶?A/cm² for MgB₂ film coated with 100?%. It?was?found that the film coated with 25?% FeO nanoparticles has slightly enhanced critical current density and it can be noted that especially the film coated with 25?% FeO became stronger in the magnetic field. The films coated with FeO were successfully produced and they indicated the presence of artificial pinning centers created by FeO nanoparticles. The superconducting transition temperature of the film coated with 25?% FeO nanoparticles was determined by moment?Ctemperature (M?CT) measurement to be 34?K which is 4?K higher than that of the pure film.     

Epitaxial Film Growth of Tl0.78Bi0.22Sr1.6Ba0.4Ca2Cu3O9 on Rolling Assisted Biaxially Textured Nickel Substrates with YSZ And CeO2 Buffer Layers

Epitaxial film growth of Tl_0.78Bi_0.22Sr_1.6Ba_0.4Ca₂Cu₃O₉ ((Tl,Bi)-1223) on rolling assisted biaxially textured substrates with YSZ and CeO₂ buffer layers (RABiTS) has been successfully demonstrated by laser ablation and post-deposition annealing in flowing argon. X-ray diffraction (XRD) -2 spectra showed that the films consisted mainly of c-axis aligned 1223 phase with some intergrown 1212 phase, while XRD -scans of (102) pole figure revealed that the films are also a- and b-axes aligned, with an epitaxy of the «100» of (Tl,Bi)-1223 film on the «110» of the top YSZ buffer layer. Four-terminal electrical transport measurements showed that the zero-resistance transition temperature (T_c) was in the range of 106 - 110 K, and the critical current density (J_c) at 77 K and zero field was about 10⁵ A/cm² for the entire film width (3 mm) of a longer film (14 mm) which was processed differently from the shorter films (7 mm). For a shorter film (7 mm) that showed better ab-in-plane alignment, the magnetization J_c, at 77 K and extrapolated to zero field, calculated from Bean's model using the full film width (3.5 mm) as the appropriate lateral dimension, was 2 × 10⁵ A/cm².     

Direct synthesis of potassium tantalate thin films by hydrothermal-electrochemical method

Single-phase potassium tantalate (KT) thin films with excellent film flatness and crystallinity have been synthesized on a tantalum substrate in 2.0 M KOH solution at 150°C by a hydrothermal-electrochemical method under a galvanostatic condition. A pyrochlore structure of the thin KT films was identified by XRD pattern analysis. The films show good adherence to the substrate and the film thickness could be as much as 2 m. The electrical properties of the films were characterized through the determination of capacitance by electrochemical impedance spectroscopy at room temperature. Dielectric constants yielded from capacitance measurements have been calculated to have values higher than 300. The dependence of cell voltage on reaction time reflects the mechanism of film formation. The preparation conditions and morphology of the films were consistent with the proposed film formation mechanism.     

Preparation and characterization of radio-frequency-sputtered Ba2Si2TiO8 thin films

Radio-frequency-sputtered barium titanium silicate (BST, Ba₂Si₂TiO₈) thin films were grown on crystalline Si (100) substrates and were characterized using wavelength-dispersive spectrometry (WDS), X-ray diffraction (XRD), optical microscopy (OM) and scanning electron microscopy (SEM), and diagonal techniques for dielectric properties. The chemical compositions of the films increasingly deviated from stoichiometry with film thickness. At the initial stage of deposition the grain configuration is dependent on the Si substrate texture. XRD analysis indicates that the BST films deposited at an optimum substrate temperature of 845 °C were strongly c-axis oriented, and that the film orientation is manipulated by substrate temperature and supersaturation. The corresponding film-growth rate in the direction normal to the film surface at 845 °C was 1.95 nm min^–1 at the initial stage, and decreased with sputtering time. The as-deposited films have a room-temperature bulk resistivity of 1.8 ×10⁷ m in the direction of thickness and an isotropic surface resistivity of 1.5×10³ m. The high-frequency relative dielectric constant, 0.05 at frequencies higher than 9 MHz, is lower than that of many typical piezoelectric materials. The high-frequency impedance character is typical of piezoelectric materials, giving a minimum impedance frequency of 9.0 MHz and a serial resonant frequency at about 9.5 MHz.     

Annealing effects on the structural and optical characteristics of electron beam deposited Ge-Se-Bi thin films

Measurements of absorbance and transmittance in Ge₂₀Se_80-xBi_x (0 x 10 at %) chalcogenide thin films in the visible range at room temperature were carried out. The dependence of the optical absorption on the photon energy is described by the relation hv=B(hv-E₀)². It was found that the optical energy gap E₀ decreases gradually from 1.93 to 1.205 eV with increasing Bi content up to 10 at %. The rate of the change decreases with increasing Bi content. The composition dependence of the optical energy gap is discussed on the basis of the concentration of covalent bonds formed in the chalcogenide film. The decrease of optical energy gap with increasing Bi content is related to the increase of Bi–Se bonds and the decrease of Se-Se bonds. The effect of thermal annealing for different periods of time on the behavior of optical absorption of the as-deposited films was investigated. The optical gap increases with increasing annealing time. The rate of change decreases with increasing annealing time, then E₀ reaches a steady state. The increase in the values of the optical gap of the amorphous films with heat treatment is interpreted in terms of the density of states model. The structure of the as-prepared and thermally annealed films were investigated using transmission electron microscopy, energy dispersive analysis and X-ray diffraction. It was confirmed that the as-prepared films were in the amorphous state. Phase separation was observed after thermal annealing. The separated crystalline phases were identified.     

Effects of molybdenum, silver dopants and a titanium substrate layer on copper film metallization

Annealing of 100 nm-thick Cu, Cu(Mo) and Cu(Ag) films was carried out to investigate the effect of dopant atoms on the films. Molybdenum (Mo) and silver (Ag) were selected as immiscible dopants for out-diffusion studies. A thermally grown SiO₂ layer and a sputtered Ti layer were used as substrates. The dopant and substrate effects were characterized in terms of surface morphology, resistivity, preferred orientation, and diffusional characteristics. The lowest observed resistivity was 2.32 · cm in the Cu(Ag) film, which was lower than that in a pure Cu film of the same thickness. Ag addition enhanced the surface morphology and thermal stability of the Cu(Ag) films. The highest thermal stability was obtained in the case of a Cu(Mo)/Ti film which maintained film integrity to 800°C. A Ti substrate enhanced Cu(111) texture growth. A highly oriented Cu(111)-texture was obtained in the Cu(Mo)/Ti films. Cu diffusion through the Ti layer was limited in the (111)-textured Cu(Mo)/Ti films, which showed good potential as a diffusion barrier.     

Effects of sputtering pressure and nitrogen concentration on the preferred orientation of AIN thin films

Aluminium-nitride films were prepared on glass substrates by reactive radio frequency (r.f.) magnetron sputtering in argon/nitrogen gas mixtures containing 25 ~ 75 1/2; nitrogen at substrate temperatures below 150C. It is important to control the crystallographic orientation and the surface morphology of the films with the deposition parameters for surface-acoustic-wave (SAW) devices. The change of crystallographic orientation with the sputtering pressure and the nitrogen concentration was calculated from the texture coefficient of the (0002) plane based on X-ray diffraction (XRD) patterns. It was found that a change of the c-axis from a parallel to a normal orientation, with respect to the substrate surface, occurred with a decrease in the sputtering pressure and an increase in the nitrogen concentration. From observations of the cross-section and the surface morphology, aluminium-nitride films exhibited a columnar structure and the grain size at the film surface increased an increase in the sputtering pressure and with a decrease in the nitrogen concentration.     

X-ray diffraction analysis of 10,12-pentacosadiynoic acid Langmuir-Blodgett films during polymerization

10,12-pentacosadiynoic acid (PCDA) LB films were deposited on two different subphases of CdCl₂ and TbCl₃ respectively and polymerized under UV-irradiation. It is found that the different subphase influenced the molecular packing, and in turn, influenced the polymerization behavior in the LB films. The molecular arrangement structures of unpolymerized and photopolymerized LB films were investigated by low angle X-ray diffraction. The periodic spacing of molecules in the LB films and the inclination angle of molecules on the substrate were calculated from the X-ray diffraction profiles. The unpolymerized PCDA LB film had one set of diffraction peaks, however, two sets of diffraction peaks were clearly observed in partly-polymerized PCDA LB films deposited on CdCl₂ subphase and reduced to one set of diffraction peaks corresponding to the polymerized LB films. On the other hand, the PCDA LB films deposited on TbCl₃ subphase had only one set of diffraction peaks throughout. This is interpreted to correspond to different mechanisms of chain propagation, i.e., heterogeneous chain propagation for the PCDA LB film deposited on CdCl₂ subphase and homogeneous polymerization for the LB film deposited on TbCl₃ subphase. A molecular arrangement model in LB film was employed to explain the phenomenon of the even-odd intensity oscillation qualitatively.     

Accuracy of energy dispersive x-ray composition analysis of YBCO films on yttrium-containing substrates as compared to Rutherford backscattering spectroscopy

We address the accuracy of Energy Dispersive X-ray Spectroscopy (EDS) composition analysis of YBa₂Cu₃O (YBCO) thin films. YBCO films deposited on yttrium stabilized zirconia (YSZ) and strontium titanate (STO) substrates were analyzed by EDS and Rutherford Backscattering Spectrometry (RBS) to determine their compositions. The YSZ substrates used in this work contained a common element, yttrium; therefore, EDS intensities of yttrium signals resulting from the film alone were calculated using EDS results of blank YSZ substrates. The EDS compositions of all the elements were obtained using the proportionality factor, k calculated from RBS data from a standard film deposited on silicon and the intensity ratios of the respective standard obtained from EDS. The film thickness was found to be an important factor to consider when choosing the optimum accelerating voltage for the EDS analysis. For films having comparable thickness to that of the standard (0.8 m), we found 25 kV was the optimum accelerating voltage for the EDS analysis that obtained compositions in good agreement with the RBS data. For films having half the thickness of the standard film, EDS composition analyses were unreliable quantitatively and were best qualitatively at 15 kV.