Structural and optical properties of (Pb,Ca)TiO3 thin films prepared by a sol-gel technique

Transparent and crack-free calcium modified lead titanate thin films were prepared on platinum-coated silicon and fused quartz substrates by a sol-gel technique. Lead acetate trihydrate, calcium nitrate tetrahydrate and titanium tetra-n-butoxide were used as starting materials. Methanol and ethanolamine were used as solvent and stabilizing agent, respectively. The structural properties of the thin films were studied by x-ray diffraction technique. Optical transmission and absorption properties of the thin films were measured in the wavelength range of 200-1100 nm. The thin films possess good optical transmissitivity. By using an approximate formula, the refractive index and band gap were evaluated. The optical transitions of the thin films are direct in nature. The dispersion relation of refractive index and wavelength follows the single electron oscillation model.     

Microstructure and optical properties of nanocrystalline Cu2O thin films prepared by electrodeposition

Cuprous oxide (Cu₂O) thin films were prepared by using electrodeposition technique at different applied potentials (−0.1, −0.3, −0.5, −0.7, and −0.9 V) and were annealed in vacuum at a temperature of 100°C for 1 h. Microstructure and optical properties of these films have been investigated by X-ray diffractometer (XRD), field-emission scanning electron microscope (SEM), UV-visible (vis) spectrophotometer, and fluorescence spectrophotometer. The morphology of these films varies obviously at different applied potentials. Analyses from these characterizations have confirmed that these films are composed of regular, well-faceted, polyhedral crystallites. UV–vis absorption spectra measurements have shown apparent shift in optical band gap from 1.69 to 2.03 eV as the applied potential becomes more cathodic. The emission of FL spectra at 603 nm may be assigned as the near band-edge emission.     

Microstructural and optical properties of Ta-doped ZnO films prepared by radio frequency magnetron sputtering

Ta-doped ZnO films with different doping levels (0–5.02 at%) were prepared by radio frequency magnetron sputtering. The effects of the doping amount on the microstructure and the optical properties of the films were investigated. The grain size and surface roughness first significantly decrease and then slowly increase with the increase of Ta doping concentration. Both the grain size and the root mean square (RMS) roughness reach their minimum values at the doping content of 3.32 at%. X-ray Diffraction (XRD) patterns confirmed that the prepared Ta-doped ZnO films are polycrystalline with hexagonal wurtzite structure and a preferred orientation along the (002) plane. X-ray photoelectron spectroscopy (XPS) analysis reveals that Ta exists in the ZnO film in the Ta⁵⁺ and Ta⁴⁺ states. The average optical transmission values of the Ta-doped ZnO films are higher than those of the un-doped ZnO film in the visible region. The band gap energy extracted from the absorption edge of transmission spectra becomes large and the near band edge (NBE) emission energy obtained from PL spectra blueshifts to high energy when the Ta doping content grows from 0 at% to 5.02 at%, which can be explained by the Burstein–Moss shift.     

水性聚氨酯脲-丙烯酸酯膜的表面性能

用预聚物分散－原位聚合法合成了聚氨酯脲－丙烯酸酯（ＰＵＡ）水分散液。用ＡＴＲ－ＦＴＩＲ和ＥＳＣＡ技术表征了ＰＵＡ水分散液在玻璃基材上成膜后的表面结构和组成,测定了不同液体在ＰＵＡ膜表面上的接触角及ＰＵＡ膜的耐磨性。结果表明,ＰＵＡ成膜时与空气接触面和与玻璃接触面的表面组成和耐磨性接近于聚氨酯脲（ＰＵＵ）的表面特性。此外,在ＰＵＡ膜中ＰＵＵ和聚丙烯酸酯的组成呈“双向梯度”分布,即在沿膜的２个表面方向     

Dielectric and optical properties of electroceramic PBZNZT thin films prepared by pulsed laser deposition process

The 0.6[0.94Pb(Zn_1/3Nb_2/3)O₃ + 0.06BaTiO₃] + 0.4[0.48(PbZrO₃) + 0.52(PbTiO₃)], PBZNZT, thin films were synthesized by pulsed laser deposition (PLD) process. The PBZNZT films possess higher insulating characteristics than the PZT (or PLZT) series materials due to the suppressed formation of defects, therefore, thin-film forms of these materials are expected to exhibit superior ferroelectric properties as compared with the PZT (or PLZT)-series thin films. Moreover, the Ba(Mg_1/3Ta_2/3)O₃ thin film of perovskite structure was used as buffer layer to reduce the substrate temperature necessary for growing the perovskite phase PBZNZT thin films. The PBZNZT thin films of good ferroelectric and dielectric properties (remanent polarization P_r = 26.0 μC/cm², coercive field E_c = 399 kV/cm, dielectric constant K = 737) were achieved by PLD at 400 °C. Such a low substrate temperature technique makes this process compatible with silicon device process. Moreover, thus obtained PBZNZT thin films also possess good optical properties (about 75% transmittance at 800 nm). These results imply that PBZNZT thin films have potential in photonic device applications.     

Hole transport in conducting ultrathin films of PEDOT/PSS prepared by layer-by-layer deposition technique

Multilayered ultrathin films of a conductive polymer, poly(3,4-ethylenedioxythiophene)/poly(4-styrenesulfonate) (PEDOT/PSS) were prepared by layer-by-layer deposition technique. These films were characterized by absorption spectroscopy, atomic force microscopy, cyclic voltammetry and potential step chronoamperometry. The PEDOT/PSS films were layered up with a bilayer thickness of 5 nm and the surface roughness of the films was improved after the ultrasonicated pretreatment of a PEDOT/PSS aqueous dispersion prior to the deposition. The ultrathin films thus obtained kept excellent diffusion constant of hole carriers, 5×10⁻¹⁰ cm² s⁻¹, as high as that of spin-cast films of PEDOT/PSS, indicating that the conducting polymer films are fabricated with nanometer-scale precision and act as a junction layer between the electrode and electrochemically active organic materials.     

Dispersive optical constants and electrical properties of nanocrystalline CuInS2 thin films prepared by chemical spray pyrolysis

Nanocrystalline CuInS₂ thin films were deposited on borosilicate glass substrates via chemical spray pyrolysis method. The structural, morphological, optical, and electrical properties were studied as a function of increasing annealing temperature from 250 to 350 ̊C. XRD analysis showed mixed phases at lower temperatures with the preferred orientation shifting towards the (112) chalcopyrite CuInS₂ plane at higher substrate temperature. The crystallite size increased slightly between 13 and 18 nm with increase in annealing temperature. The optical band gap was determined on basis of Tauc extrapolation method and the Wemple–Di-Domenico single oscillator model. Possible structural and quantum confinement effect may have resulted in relatively larger band gaps of 1.67–2.04 eV, relative to the bulk value of 1.5 eV. The presence of Cu_xS in the as-deposited and wurtzite peaks after annealing at 350 ^̊C play a role in influencing the optical and electrical properties of CuInS₂ thin films.     

Electrical and optical properties of Al-doped ZnO and ZnAl2O4 films prepared by atomic layer deposition

ZnO/Al₂O₃ multilayers were prepared by alternating atomic layer deposition (ALD) at 150°C using diethylzinc, trimethylaluminum, and water. The growth process, crystallinity, and electrical and optical properties of the multilayers were studied with a variety of the cycle ratios of ZnO and Al₂O₃ sublayers. Transparent conductive Al-doped ZnO films were prepared with the minimum resistivity of 2.4 × 10⁻³ Ω·cm at a low Al doping concentration of 2.26%. Photoluminescence spectroscopy in conjunction with X-ray diffraction analysis revealed that the thickness of ZnO sublayers plays an important role on the priority for selective crystallization of ZnAl₂O₄ and ZnO phases during high-temperature annealing ZnO/Al₂O₃ multilayers. It was found that pure ZnAl₂O₄ film was synthesized by annealing the specific composite film containing alternative monocycle of ZnO and Al₂O₃ sublayers, which could only be deposited precisely by utilizing ALD technology.     

Properties of CNx films prepared by PECVD

For this project, CN_x films were prepared by the plasma-enhanced chemical vapour deposition (PECVD) method. Two kinds of substrate were chosen for film deposition: Cr–Ni–Mo steel (0.095 C, 17.25 Cr, 12.04 Ni, 2.49 Mo) and silicon. The substrates were prepared in the shape and size needed for the planned measurements. The surfaces for film deposition were polished and the substrates cleaned in organic solvents by means of ultrasound before treatment. The following CN_x film properties were investigated: thickness, internal stress, dependence of the friction coefficient on the load, refraction index and contamination. For the investigation of these properties the following methods or instruments were chosen: Talystep profilometer, the optical method of stress measurement based on macroscopic sample bending, tribometer HEF, ellipsometry, Rutherford backscattering spectroscopy (RBS) and electron probe microanalysis (EPMA). The thickness values fell in the range of hundredths of nanometres. The compressive stress of the films was below 0.8 GPa. The friction coefficient decreased when the load value increased. There was remarkable oxygen contamination in the prepared films.     

A correlation between the microstructure and optical properties of hydrogenated amorphous carbon films prepared by RF magnetron sputtering

Comparative and systematic studies of the effect of the radiofrequency (RF) bias on the microstructure and the optical properties of hydrogenated amorphous carbon (a-C:H) have been carried out on films deposited by RF magnetron sputtering under different RF power varying from 10 to 250 W applied to the graphite target, leading to a negative bias voltage at the target in the range of −60 to −600 V.A combination of infrared (IR) absorption experiments, which give information about the local microstructure (i.e. C–C and C–H bonding), and optical transmission measurements in the UV-visible and near IR, from which we determined the optical gap E₀₄ and the refractive index n, are applied to fully characterize the samples in their as-deposited state. The results show first that the films deposited at low RF power (i.e. low negative bias) exhibit a more open microstructure (polymeric character) with a lower density than those deposited at high RF power (i.e. high negative bias). They also indicate that the total bonded H content as well as the sp³/sp² ratio of carbon atoms bonded to H decrease with increasing RF power leading to the formation of higher proportions of C-sp² sites. The same tendency is observed for the optical gap E₀₄. On the contrary, the refractive index increases with increasing RF power, suggesting the densification of the films in going to a higher RF power.     

Optimizing the processing conditions of sodium potassium niobate thin films prepared by sol-gel spin coating technique

In the present study, potassium sodium niobate (KNN) thin films were synthesized by means of sol-gel spin coating method. Along with the synthesis, the effects of annealing temperature and various number of coating layers on both the structural and electrical properties were looked into. The results of the study revealed that the annealing temperature had a great impact on the properties of KNN. In addition, the XRD diffractograms and texture coefficient of the synthesized films confirmed that a highly oriented orthorhombic perovskite structure was obtained at 650 °C, whereas at a relatively higher temperature (700 °C), a spurious phase of K₄Nb₆O₁₇ was evolved. In addition, the growth of KNN at 650 °C exhibited a reasonable resistivity value for piezoelectric applications. Looking into the results, it was discovered that the KNN thin films also found to be dependent on a number of coating layers. Field emission scanning electron microscopy (FESEM) showed that KNN with five coating layers was highly crystalline, cracks-free, and had significantly more homogenous surface morphology and the size of grains being uniform, the resistivity of KNN thin films improved with the increasing number of coating layers i.e., up to five.     

Dielectric properties of Mn doped Bismuth Barium Titanate based ceramic thin films prepared by PLD technique

In this article, the effect of Mn doping on the permittivity and dielectric loss in 0.67BiFeO₃-0.33BaTiO₃ (BF-BT) based film bulk acoustic resonator test structures has been investigated. BF-BT thin films were deposited on the fused silica substrates with Pt/TiO₂/Ti as bottom electrode. During the study of the BF-BT based parallel-plate structures, it has been revealed that BF-BT is in the ferroelectric state at room temperature. Higher permittivity (ԑ) is observed at a growth temperature of 600 °C and lower dielectric loss is achieved at 0.3 wt% Mn doping contents. These results show that the proposed BF-BT based FBAR test structure has a great potential for applications in tunable thin Film Bulk Acoustic Resonator (FBAR) devices. Comparison of the measured and simulation results has been made by utilizing the Mason equivalent circuit.     

TiO2 nanoceramic films prepared by ion beam assisted evaporation for optical application

A TiO₂ nanoceramic film was prepared as an alternative absorber layer for infrared thermal detectors. The TiO₂ film was amorphous, and its grain size increased with the ion anode voltage and oxygen flow rate. Moiré deflectometry was applied for measuring the nonlinear refractive indices of TiO₂ films on polycarbonate (PC) substrates. The nonlinear refraction index was measured to be of the order of 10⁻⁸ cm² W⁻¹ and the change in refractive index was of the order of 10⁻⁵. The linear refractive index was correlated with the porosity. Denser TiO₂ films exhibited higher linear refractive indices, obvious red-shifts and narrower absorption bands in the near-IR region.     

Alon-based materials prepared by SHS technique

The aim of the presented paper was preparation of the highly reactive in the sintering powders in the Al–O–N system by SHS method. Combustion reactions of metallic aluminium and corundum powder mixtures (from 15% Al–85% Al₂O₃ to 50% Al–50% Al₂O₃) were performed in nitrogen atmosphere. The obtained powders were ground and hot-pressed at 1750, 1850 and 1950 °C for 1 h under 25 MPa in nitrogen flow. In contrast to conventional methods, which require 24 h of the precursor heat treatment at 1200 °C our studies, showed that it is possible to prepare almost pure γ-alon materials using SHS reaction. Sintering of the powders led to obtained dense materials composed of pure γ-alon or γ-alon–AlN composites. The phase composition of the sintered bodies was controlled by the chemical composition of the starting mixture and the sintering temperature.     

Surface analysis of poor printability PVC films

Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS) were employed to analyze the surfaces of PVC films with poor printability. FTIR indicated that, independent of formulation, the migrating species were metal carboxylates. Different techniques penetrate the surface to different depths allowing examination of a range of surface layers. XPS indicated that, in the worst case, the upper surface layer was comprised almost exclusively of a mixed metal carboxylate. Atom percentages obtained by XPS indicated hydrolysis of the mixed metal carboxylate at the vinyl surface.     

Structure and mechanical properties of W incorporated diamond-like carbon films prepared by a hybrid ion beam deposition technique

W incorporated diamond-like carbon films were prepared on silicon(1 0 0) wafers using a hybrid deposition system composed of an end-Hall-type hydrocarbon ion gun and a tungsten DC magnetron sputter source. The W concentration in the films was controlled by changing the fraction of Ar in the Ar and C₆H₆ reaction gas. The chemical composition, atomic bond structure, and mechanical properties were investigated for W concentrations ranging from 0 to 8.6 at.%. When the W concentration was <2.8 at.%, the W atoms were dissolved in the amorphous carbon matrix without forming a WC_1−x phase. Amorphous and crystalline WC_1−x nano-particles appeared when the W concentration was >2.8 and >3.6 at.%, respectively. It was found that the hardness and elastic modulus were not sensitive to the W concentration in this concentration range. On the other hand, the residual compressive stress was strongly dependent on the chemical state of the incorporated W atoms. The change in mechanical properties is discussed in terms of the microstructural changes induced by W incorporation.     

Structural,morphological, and optical properties of W-doped VO2 thin films prepared by sol-gel spin coating method

Thermochromic VO₂ thin films were deposited on soda-lime glass via sol-gel method. Doping was done through adding tungstic acid solution to the vanadium solution precursor. Grazing incidence x-ray diffractometer (GIXRD) results showed that VO₂ and V₆O₁₃ phases were formed together in the heat-treated sample. According to the GIXRD result of the W-doped sample, only VO₂ remained. Field-emission scanning electron microscopy (FESEM) micrographs showed that the VO₂ grain size decreased from about 70 to about 25 nm for undoped film and 2 wt% W-doped films, respectively. Atomic force microscopy (AFM) results showed that the root mean square roughness for the film with 180 nm thickness was about 18 nm, and 2 wt% W-doped film had a smoother surface. Diffuse reflectance spectroscopy (DRS) results showed that the band gap energy for undoped, 1 wt% W- doped, and 2 wt% W-doped VO₂ thin films was 1.7, 1.3, and 0 eV, respectively. Four-point probe resistivity measurements showed a significant decrement, from approximately 1 MΩ at 15°C to <100 Ω at 80°C. Regarding Vis-NIR spectroscopy results, maximum optical transmission for undoped and W-doped films was approximately 75% and 35%, respectively.     

Surface analysis and adhesion properties of coalesced latex films

The surface composition of films obtained from acrylic latexes (45 wt% MMA, 55 wt% BuA) stabilized by two anionic surfactants (either sodium dodecyl sulphate (SDS) or sodium dodecyl diphenyl ether disulphonate (SDED) has been studied by attenuated total reflection with Fourier transformed infrared spectroscopy (ATR-FTIR), X-ray photoelectron spectroscopy (XPS) and secondary ion mass spectrometry (SIMS). The results of this surface analysis are summarized and used to interpret adhesion properties of the films on glass substrate. Adhesion properties were derived from peeling tests. In the case of SDED, the peel strength increases with surfactant surface concentration. This is due to strong polar interactions between the hydrophilic part of the surfactant and the polar groups of the glass surface and to the anchorage of the hydrophobic part of the surfactant in the copolymer matrix. In the case of SDS, the peel strength decreases with increasing surfactant surface concentration. The same polar interactions as with SDED exist, but the SDS layer at the interface is very thick. It forms what is called a ‘weak boundary layer’ in which rupture propagates easily.     

Effect of Fe-doping on the structural,optical and magnetic properties of ZnO thin films prepared by RF magnetron sputtering

In this paper, we report the fabrication and systematic characterization of Fe Doped ZnO thin Films. Fe_xZn_1−x O (x=0<0.05) films were prepared by RF magnetron sputtering on Si (400) substrate. Influence of Fe doping on structural, optical and magnetic properties has been studied. The X-ray diffraction (XRD) analysis shows that Fe doping has affected the crystalline structure, grain size and strain in the thin films. The best crystalline structure is obtained for 3% Fe Doping as observed from Atomic Force Microscopy (AFM) and X-ray diffraction (XRD). The magnetic properties studied using Vibrating Sample Magnetometer reveals the room temperature ferromagnetic nature of the thin films. However, changing the Fe concentration degrades the magnetic property in turn. The mechanism behind the above results has been discussed minutely in this paper.     

Mn-doped titania thin films prepared by spin coating

TiO₂ thin films doped with ≤7 mol% Mn (metal basis) were deposited on F-doped SnO₂-coated (FTO) glass substrates by spin coating. The structural, morphological, and optical properties of the films were investigated by glancing angle X-ray diffraction (GAXRD), laser Raman microspectroscopy, field emission scanning electron microscopy (FESEM), and ultraviolet–visible spectroscopy (UV–VIS). Mn doping of TiO₂ (anatase) extended the optical absorption edge to longer wavelengths (lower photon energies) significantly lowering the band gap from 3.32 eV (undoped) to 2.90 (7 mol% Mn). The absorption edges of all films were sharp and the transparencies in the visible region were in the range 60–75%. All of the films were homogeneous, fully dense, and essentially crack-free.