Nonlinear optical response of titanium oxide nanostructured thin films

Titanium (IV) oxide thin films prepared by low temperature (95 °C) hydrothermal growth were observed to undergo important structural modifications upon variation of the deposition period, modifications strongly affecting the nonlinear optical (NLO) response of the films. Depending on the growth time, the films were observed to contain anatase or rutile TiO₂. It was found that only anatase TiO₂ exhibits significant nonlinear optical response.     

Study on spray deposited Ni-doped CuO nanostructured thin films: microstructural and optical behavior

Journal of Materials Science: Materials in Electronics - In this study, CuO and Ni-doped CuO thin films are deposited on glass substrates at 400 °C by the spray pyrolysis as easy,...     

Electrical,optical and magnetoresistive behavior of nanostructured ZnO:Cu thin films deposited by sputtering

Copper doped ZnO (ZnO:Cu) nanostructured films with magnetoresistive behavior were produced by growing ZnO/Cu/ZnO arrays at room temperature (RT) by the sputtering technique on corning glass substrates. The arrays were made with two electrical insulating ZnO films of 50 and 105 nm, and a Cu film of 5 nm, both materials were deposited at RT by the RF- and DC-sputtering technique, respectively. The processing method involves two stages that proceed in the course of the growth process, the main one is originated by the non-equilibrium regime of the sputtering technique, and the second is the diffusion-redistribution of the intermediate Cu film towards the neighborhood ZnO layers aided by the nanocrystalline films character. The influence of applying an additional annealing stage to the arrays in N₂ atmosphere at 250 and 350 °C by periods of 30 min were studied. The resistivity of the ZnO:Cu films can be varied from 0.0034 to 2.83 Ω-cm, corresponding to electron concentrations of 1.12?×?10²¹ and 7.85?×?10¹⁷ cm^?3 with carrier mobility of 1.6 and 2.8 cm²/V s. Measured changes on the magnetoresistance behavior of the films at RT were of ?R?~?3% for annealed samples with electron concentration of 1.12?×?10²¹ cm^?3. The X-ray diffraction measurements show that the films are comprised of nanocrystallites with dimensions between 13 and 20 nm in size with preferred (002) orientation. The transmittance of the films in the visible region was of 83% with an optical band gap of ~?3.3 eV for the low-resistivity samples.     

Monitoring the arbitrary thickness of optical thin films and their error simulation: a method

This paper was the method of monitoring the absolute value for film layer transmittance to monitor the thickness of optical thin film. For this purpose, a 2S3G double-color three-path monitoring apparatus was built. Simulation analyses of monitoring errors have been conducted and a flow diagram is given. Using this method and apparatus, 9-, 15-, and 23-layer broadband neutral dichroic filters, cold light coatings, edge filters, and polarizers have been plated; good reproducibility and satisfactory results have been obtained, thereby achieving the preparation of the non-lambda/4 multilayer system     

Preparation,characterization and optical properties of nanostructured ZnO thin films

Nanostructured ZnO thin film on a glass slide has been prepared by the spin-coating method together with calcining at 500 °C for 2 h in flowing oxygen atmosphere. The grain size of the ZnO nanoparticles is estimated to be ca. 12 nm as determined by the absorption spectrum and powder X-ray diffraction analysis. The photoluminescent peaks that centered at ca. 379 and 388 nm are assigned to the spontaneous emission and exciton–exciton emission, respectively. The thin film also shows frequency-tripled properties for the output when the laser beam of 1.06 μm is input in convergent beam.     

Size dependent optical characteristics of chemically deposited nanostructured ZnS thin films

ZnS thin films of different thicknesses were prepared by chemical bath deposition using thiourea and zinc acetate as S²⁻ and Zn²⁺ source. The effect of film thickness on the optical and structural properties was studied. The optical absorption studies in the wavelength range 250–750 nm show that band gap energy of ZnS increases from 3·68–4·10 eV as thickness varied from 332–76 nm. The structural estimation shows variation in grain size from 6·9–17·8 nm with thickness. The thermoemf measurement indicates that films prepared by this method are of n-type.     

Diethynyl-Zn-porphyrin-based assemblies: optical and morphological studies of nanostructured thin films

In this paper, we focus our attention on the morphological and optical characterisation of self-assembled Zn-porphyrin-based/fullerene systems. Diethynyl-Zn-porphyrin (ZnDEP) and bimetallic σ-bonded arrays of diethynyl-Zn-porphyrin with Pd(II) and Pt(II) square planar complexes, namely, ZnDEP, Pd–ZnDEP and Pt–ZnDEP, have been synthesised, and these compounds were studied in the self-assembly behaviour with fullerene, giving rise to the molecular composites ZnDEP/C₆₀, Pd–ZnDEP/C₆₀ and Pt–ZnDEP/C₆₀. Thick films of the materials were deposited by slow evaporation on glass substrates, in order to be morphologically characterised by scanning electron microscopy (SEM) technique. The surface analysis showed a peculiar nanometric structure of the composites. The optical (UV–Vis absorption and emission) characterisation of toluene solutions and a preliminary study on the molecular oxygen luminescence quenching of diethynyl-Zn-porphyrin, diethynyl-Zn-porphyrin/fullerene and platinum or palladium-containing homologues have been performed and will be here discussed. A luminescence response towards molecular oxygen was observed in the case of ZnDEP and ZnDEP/C₆₀ samples with a lowering of the intensity of the emission, suggesting promising applications in optical sensors.     

Electrochromic and morphological investigation of dry-lithiated nanostructured tungsten trioxide thin films

Electrochromic properties of porous nanostructured thin films of tungsten trioxide were investigated. Films were fabricated at normal and high vapor incidence angles with the technique of glancing angle deposition in a thermal evaporation chamber. A dry lithiation method was subsequently used to intercalate films with lithium atoms. Coloration in both visible and near-infrared regions was observed with lithium insertion. We report on the morphology, porosity, and optical properties of as-deposited and lithiated films, and discuss the role of substrate tilt in comparing the coloration efficiency of these films.     

Ferroelectric behavior in bismuth ferrite thin films of different thickness

The ferroelectric behavior of BiFeO(3) thin films is modified by changing the film thicknesses, where the BiFeO(3) thin films with different thicknesses were grown on SrRuO(3)/Pt/TiO(2)/SiO(2)/Si(100) substrates by radio frequency sputtering. The mixture of (110) and (111) orientations is induced for all BiFeO(3) thin films regardless of their thicknesses, together with the columnar structure and the dense microstructure. Their dielectric behavior is almost independent of the film thickness where all thin films have a low dielectric loss. A giant remanent polarization of 2P(r) ≈ 156.6-188.8 μC/cm(2) is induced for the BiFeO(3) thin films in the thickness range of 190-600 nm. As a result, it is an effective way to improve the ferroelectric behavior of the BiFeO(3) thin film by tailoring the film thickness.     

The influence of films thickness on hydrogenation behavior of titanium thin films

Titanium films of different thicknesses were prepared on sapphire substrates in an UHV chamber, by means of ion beam sputter deposition at room temperature, under Ar-atmosphere at the pressure of 1.5·10 E^?4 mbar. For electrochemical hydrogen loading, the films were covered by a 30-nm thick layer of Pd in order to prevent oxidation and facilitate hydrogen absorption. In situ stress measurements were conducted during step-by-step electrochemical hydrogen charging of the films. XRD measurements using a Phillips X-Pert diffractometer with a Co-Kα radiation were performed before and after hydrogenation in order to investigate the effect of hydrogen loading on the microstructure. The phase boundaries, as well as the stress and strain development during hydrogen absorption, depend strongly on the thickness of the films. The main characteristics of absorption behavior of hydrogen, as well as the thermodynamics and phase boundaries of titanium–hydrogen thin films are discussed in detail with specific emphasis on the influence of films thickness. The obtained results are also compared to literature data on the widely studied titanium–hydrogen bulk system. Shifted phase boundaries and narrowed two-phase field appear in Ti–H film system, which are mainly attributed to the microstructural contribution, as well as to the large stresses in the GPa-range that built up between the films and their substrate.     

Modified needle method with simultaneous thickness and refractive-index refinement for the synthesis of inhomogeneous and multilayer optical thin films

Useful features of an efficient thin-film synthesis technique based on the refinement of inhomogeneous films are adapted to the needle method. As in the former approach, all the layer refractive indices and thicknesses are refined simultaneously, and special attention is given to computation speed and accuracy. In particular, key parameters are calculated from analytical formulas, namely, the gradients used in the optimization routines and the optimum needle positions and refractive indices. Inhomogeneous as well as multilayer solutions are possible. The efficiency of the modified approach is demonstrated by the solution of a complex nonpolarizing, wide-angle antireflection coating problem. The results are compared with those obtained in the past by the conventional needle method and by refinement of inhomogeneous films.     

Third order optical nonlinearities in CdS nanostructured thin films: a comprehensive review

Journal of Materials Science: Materials in Electronics - This paper is focused on optical nonlinearity in CdS nanostructured thin films, which was reviewed comprehensively and discussed in detail...     

An investigation of the optical properties of plasma-polymerized diphenyl thin films

Highly adhering plasma-polymerized diphenyl (PPDP) thin films were grown by a dry and flawless process in glow discharge. The structural analyses of as-deposited and heat treated PPDP samples (unaged and aged) were performed by infrared (IR) spectroscopy. The PPDP thin films were transparent and light yellow in colour. Optical properties were evaluated from ultraviolet–visible (UV–Vis) spectroscopic measurements of as-deposited, heat treated and aged (as-deposited and heat treated) PPDP thin films. From the optical absorption data band gaps, allowed direct and indirect transition energy gaps were determined. The results are discussed in the light of possible structural modification in PPDP thin films on heat treatment and aging.     

Electrical modeling of nanostructured thin films

Electric circuit networks based on lumped components and distributed impedance elements are considered in the analysis of impedance spectroscopy data of nano-structured materials. A procedure based on transformation among degenerate networks is used as synthesis of linear, passive, one-port electric schemes and non-distinguishable distributed elements due to the noise level in observed data. Experimental results obtained on nitrogen doped ultra-nanocrystalline-diamond thin films are used to illustrate this process.     

Luminescent method for measuring the thickness of thin coating films on rough surfaces

Conclusions A luminescent method has been developed for evaluating the thickness of thin transparent luminescent coatings on surfaces of solid bodies by means of an equipment consisting of instruments produced by our industry.The high sensitivity of photomultipliers and the high definition of their luminous beam (of the order of 1 ²) are suitable for measuring the surface of thin films either at separate points, or for plotting their thickness diagrams along a definite path of the tested surface.This method can be recommended for evaluating oil coatings over rough metal surfaces. The method used for this purpose to date has consisted of applying lubricating layers of volatile solvents, with their thickness being evaluated by computation from the concentration of the solution and the area which it covered. This method contributes considerable errors. First, it is assumed that an oil film of a definite thickness is thus produced, whereas even on a smooth surface the oil is distributed nonuniformly, and all the more so on a rough surface. Second, the true area of a rough surface is not known, and it is assumed in calculations that the surface is smooth. These errors can be reduced by using the luminescent method.The same technique can be used for evaluating the distribution of lubricants over a friction path, for testing the uniformity and continuity of certain decorative or insulating coatings, etc.Thus, the measurement of film thicknesses by the luminescent method can be used both in scientific research and in industry.Translated from Izmeritel'naya Tekhnika, No. 9, pp. 27–29, September, 1967.     

Fiber-optic surface-plasmon resonance for the determination of thickness and optical constants of thin metal films

We demonstrate that the thickness and the dielectric constants of thin gold films deposited on the surface of a fiber core can be quantitatively determined as a single set of solutions by the simple measurement of the fiber-optic surface-plasmon resonance responses. This method is capable of directly characterizing metal films with curved surfaces: this is very hard to perform by use of the conventional optical techniques of reflectometry and ellipsometry. The theoretical errors for the experimental fiber are estimated to be within d +/- 2%, epsilon(r) +/- 1%, and epsilon(i) +/- 15%.     

High coercivity in nanostructured Co-ferrite thin films

Three methods including sol-gel, rf sputtering and pulsed laser deposition (PLD) have been used for the fabrication of high coercivity Co-ferrite thin films with a nanocrystalline structure. The PLD method is demonstrated to be a possible tool to achieve Co-ferrite films with high coercivity and small grain size at low deposition temperature. High coercivity, over 10 kOe, has been successfully achieved in Co-ferrite films with a thickness of ∼ 100 nm deposited using PLD with a substrate temperature at 550°C. The Co-ferrite films prepared by PLD at over 300°C on different substrates including amorphous glass, quartz and silicon exhibits an obvious (111) textured structure and possesses perpendicular anisotropy. Our study has also shown that the high coercivity is related with a large residual strain, which may induce an additional magnetic anisotropy (stress anisotropy) and at the same time serve as pinning centres, which can restrict the domain wall movement and therefore, increase the coercivity.     

Structural and optical investigation of spray-deposited SnO2 thin films

Journal of Materials Science: Materials in Electronics - A study of the investigation of tin oxide (SnO2) thin films deposited by spray pyrolysis method was undertaken by analysing the structural...