Effect of the nanographite film thickness on the optical rectification pulse

The phenomenon of optical rectification during pulsed laser irradiation was studied in nanographite films of various thicknesses obtained by plasmachemical deposition on silicon substrates. The amplitude of the optical rectification pulse (ORP) strongly depends on the film thickness h and reaches a maximum at h ∼ 2.5 μm. At a smaller film thickness, the ORP is accompanied by a photoelectric signal of microsecond duration, which arises in the silicon substrate. For the nanographite films with h > 2.5 μm, the ORP is observed in the absence of any signal from the substrate, which allows such films to be used in fast-response detectors of pulsed laser radiation in a broad spectral range.     

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.     

Synthesis and characterizations of CdS nanorods by SILAR method: effect of film thickness

In this investigation, we have successfully synthesized CdS nanorods by simple and inexpensive successive ionic layer adsorption and reaction (SILAR) method. The effect of film thickness on the physico-chemical properties such as structural, morphological, wettability, optical, and electrical properties of CdS nanorods has been investigated. The XRD pattern revealed that CdS films are polycrystalline with hexagonal crystal structure. SEM and TEM images showed that CdS film surface are composed of spherical grains along with some spongy cluster and an increase in film thickness up to 1.23 μm causes the formation of matured nanorods having diameter 150–200 nm. The increases in water contact angle form 105° to 130° have been observed as film thickness increases from 0.13 to 1.23 μm indicating hydrophobic nature. The optical band gap was found to be increased from 2.02 to 2.2 eV with increase in film thickness. The films showed the semiconducting behavior with room temperature electrical resistivity in the range of 10⁴–10⁶ Ω cm and have n-type electrical conductivity.     

Magnetic anisotropy of electrodeposited Co--P amorphous alloys

The development of magnetic anisotropy with regard to thickness in amorphous electrolytic Co-P alloys (15 at % P) has been observed in the range of thicknesses between 0.06-7.00μm. The study has been undertaken starting from the ratio Mr/Msof the hysteresis loops. The results obtained indicate that for thicknesses below 4000 Å the samples show an axis of easy magnetization in the plane. In the case of greater thicknesses, the axis of easy magnetization develops gradually out of the plane, reaching a perpendicular position near 10 μm. Our results suggest that what we are dealing with here is a shape anisotropy such as that proposed by Cargill, III et al.     

Low-temperature deposition of rutile film on biomaterials substrates and its ability to induce apatite deposition in vitro

Low-temperature deposition of crystalline titania films on intrinsically bioinert materials to induce the bioactivity is of practical interest, not only because it meets the demand of providing organic biomaterials with bioactivity, which cannot tolerate high-temperature thermal treatments, but also because it reserves abundant Ti–OH groups facilitating the apatite deposition. In this paper, rutile films with thickness varied from 0.1 μm to 1.7 μm were deposited on commercially available pure titanium substrates from 1.5 M titanium tetrachloride aqueous solution kept at 60 °C for 3–60 h. The rutile films grew to give a preferred (101) crystalline plane in the X-ray diffraction pattern. After soaking in a simulated body fluid of the Kokubo solution (SBF) for 2 days, the rutile films with thickness over 0.6 μm were covered with a layer of apatite. All the films with various thickness induced apatite deposition in SBF after soaking for 5 days. The bioinert polytetrafluoroethylene (PTFE) was also found to exhibit remarkable in vitro bioactivity as to induce apatite deposition from SBF within 2 days, after depositing the rutile film on the surface. This work is supported partly by the Natural Science Foundation of Zhejiang Province under the project No. M503011.     

Thermal stability of fcc structure in FeNi films of various thicknesses

Thin films of a polymorphous iron-nickel (FeNi) alloy with a nickel content of 25–30% and a thickness from 0.1 to 1.3 μm have been obtained by thermal deposition in vacuum in a setup with turbomolecular pumps. The phase transitions in these FeNi films have been studied by X-ray diffraction and magnetic phase analysis. The results of these measurements show that the crystallographic stability of a face-centered cubic (fcc) structure in a temperature interval from 70 to −196°C depends on the film thickness. It is suggested that this dependence is determined by crystal structure defects, the density of which is proportional to the film thickness and grain size. It is also established that substrate type does not influence the temperature interval for the existence of stable crystallographic modifications in the sample studied. The results can be used for determining the optimum composition and thickness of a working FeNi layer in thermovoltaic recording media, ensuring a wide operating temperature range.     

Measuring the thickness of thin liquid films on solid surfaces using the laser-induced thermocapillary response

A contactless method based on the laser-beam-induced thermocapillary effect is proposed for measuring the thickness of a thin liquid film on a flat solid surface. The method can be also used to measure the films with inhomogeneous thicknesses formed on a nonhorizontal substrate.     

Scaling down of organic thin film transistors: short channel effects and channel length-dependent field effect mobility

Organic thin film transistors with P3HT (poly-3-hexylthiophene) as active semiconducting layer, channel lengths from 0.3 to 20 μm, and gate oxide thicknesses from 15 to 170 nm have been successfully fabricated on Si substrates. The measurement results show that the channel length over oxide thickness ratio should be large enough (i.e., the vertical electric field should be at least 10 times higher than the lateral electric filed) in order to suppress the short channel effects of transistors. The field effect mobility of long channel devices (L ≥ 5 μm) is about an order of magnitude larger than small channel devices (L from 0.3 to 2.5 μm), which could be attributed to the more severe contact resistance effects between organic materials and metal contacts for devices with smaller dimensions.     

A set of gauges for measuring the thickness of nickel coatings on an aluminum alloy

Technological features of the manufacture of sets of thickness gauges for use in measuring the thickness of nickel coatings on the D16T aluminum alloy up to 100 μm with error 0.12–0.63 μm (0.4–0.6%) sufficient for inspection of thickness gauges with standard error at least 1% are presented. Translated from Izmeritel’naya Tekhnika, No. 3, pp. 22–23, March, 2009.     

Investigation of aluminium thin layer microstructure on BOPP polymer substrate

In this work, 40 μm biaxially oriented polypropylene (BOPP) polymer substrate is coated in a roll coater system. The single- and double-coated aluminium thin layers are analyzed by XRD, SEM, TEM, AFM and optical light microscopy. The size and density of pinholes are investigated by using TEM, the size of the pinholes are in the range of 0.8–8 μm, it is shown that with increasing sample thickness, the dimension of pinholes decreases. SEM and AFM are applied to study the surface morphology. The results show that the surface roughness of double-coated film is better than the single-coated one and the size of pinholes is smaller. The transmittance through the samples is measured on the UV–Vis range. The results show that double-coated film has significantly low transmittance (almost zero transmittance) in UV–Vis region.     

Photoresponse of n -ZnO/ p -Si heterojunction towards ultraviolet/visible lights: thickness dependent behavior

A series of n-ZnO/p-Si thin film heterojunctions have been fabricated by a low cost sol–gel technique for different ZnO film thicknesses and the dark as well as photo current–voltage (I–V) characteristics have been investigated in details. The heterojunction with ZnO thickness of 0.46 μm shows the best diode characteristics in terms of rectification ratio, I _F/I _R = 5.7 × 10³ at 5 V and reverse leakage current density, J _R = 7.6 × 10⁻⁵ A cm⁻² at −5 V. From the photo I–V curves and wavelength dependent photocurrent of the heterojunctions, it is found that the junction with 0.46 μm ZnO thickness shows the highest sensitivity towards both UV and visible lights.     

Thermal wave measurement of wet paint film thickness

Thermal wave phase measurements are reported on the drying of wet paint films on aluminium substrates. Measurements of the change in thickness as the paint dries have also been obtained using a differential focussing technique on an optical microscope. By including the optical microscope measurements of the drying paint film thickness together with estimates for the density and thermal properties of the drying and cured paint, predictions have been made of the thermal phase/thickness relationships for the wet, dry, curing and cured paints. It is concluded that a phase measurement on the wet paints could be used to predict a final cured paint thickness with an accuracy of approximately ±2 μm. Errors in predicting cured film thickness from a wet film thermal phase measurement arises principally from uncertainty over the solvent content of the wet paint film, the state of cure, and the consequent uncertainty over the paint density and thermal properties.     

Magnetostriction and microstructure of the melt-spun Fe83Ga17 alloy ribbons

Fe₈₃Ga₁₇ alloy ribbons with four thicknesses were prepared by the melt-spun method. The measured results show that magnetostriction is related to the thickness of the ribbons, and its maximum value, −2100 ppm, has been obtained in the ribbon with a thickness of 75 μm. The results of the X-ray diffraction (XRD) and the differential scanning caloric (DSC) show that a phase with DO₃ structure emerges in those ribbons with the thicknesses of 45, 55 and 75 μm, and a phase transition of A2 + DO₃ → A2 occurred at 669°C for the ribbon with the thickness of 75 μm. The increase in the cooling rate can restrain the precipitation of the Ga-rich phase in the ribbon. It is considered that the giant magnetostriction of ribbons originates from the A2 + special DO₃ structure and shape magnetic anisotropy. Translated from Acta Metallurgica Sinica, 2006, 42(2): 177–180 [译自: 金属学报]     

High-throughput dynamic impact characterization of polymer films

An instrumented falling weight impact apparatus has been designed and constructed for high-throughput characterization of polymer films in the 5–100 m thickness range. The primary intended use of the instrument is rapid and accurate characterization of the dynamic impact response of multiple (100) positions on a combinatorial library film. This will allow future exploration of the dependence of mechanical response on polymer composition, thickness, and annealing temperature using combinatorial synthesis and characterization methods. This paper describes the instrument and presents validation measurements using polyethylene films of uniform thickness (25 m) and poly(urethaneurea) elastomers of thicknesses from 10–30 m. Measurements on the polyethylene film demonstrate the reproducibility and lack of interaction effects for multiple measurements on the same film. Poly(urethaneurea) elastomer impact measurements are used to indicate the instrument sensitivity to controlled variations in polymer chemistry and structure. In particular, the results from force-deformation profiles indicate an optimum curing temperature and the expected trend in mechanical response with respect to polyurethaneurea diamine chain extender composition.     

Waveguide spectroscopy of thin films

A waveguide method of measurement of the absorption spectra of thin films in the range of their transparency is considered. The absorption spectra obtained by this method for the thin films of tin oxide and zinc oxide in a wavelength range from 400 to 800 nm are presented. The error of measurement of the absorption spectrum did not exceed 5% for an ∼0.1-μ-thick film with an absorption coefficient of ∼50 cm⁻¹. Possibilities and limitations of the method are discussed.     

Simultaneous determination of the optical indices of an absorbant film and its metallic substrate by statistical analysis of spectroreflectometric data: Application to the oxide/titanium system

A method to compute the optical indices of a thin absorbant film, together with those of its metallic substrate, from a statistical analysis of the reflectance changes with film thickness d of the metal-film system is given. The results are applied to anodic oxide films grown on titanium. The accuracy of the indices of the titanium substrate is shown to be a function of the ratio of the film thickness to the wavelength. By using films with thicknesses ranging between 10 and 2500 Å, the optical indices in a wavelength range 0.25–2.5 μm were obtained. The titanium indices are compared with results recently cited in the literature; the accuracy of our result, for instance in the determination of the bulk plasmon frequency, is demonstrated.     

Structural and optical properties of Ag2SeTe nano thin films prepared by thermal evaporation

Semiconducting Ag₂SeTe thin films were prepared with different thicknesses onto glass substrates at room temperature using thermal evaporation technique. The structural properties were determined as a function of thickness by XRD exhibiting no preferential orientation along any plane, however the films are found to have peaks corresponding to mixed phase. The XRD studies were used to calculate the crystallite size and microstrain of the Ag₂SeTe films. The calculated microstructure parameters reveal that the crystallite size increases and micro strain decreases with increasing film thickness. The refractive index, dielectric constants and thereby the optical bandgap of the films were calculated from transmittance spectral data recorded in the range 400?C1200 nm by UV?CVIS-Spectrometer. The direct optical bandgap of the Ag₂SeTe thin films deposited on glass substrates with different thicknesses 50?C230 nm were found to be in the range 1.48?C1.59 eV. The carrier density value is estimated to be around 9.8 × 10²¹ cm^?1 for the film thickness of 150 nm. The compositions estimated from the optical band gap studies reveal a value of 0.75 for Tellurium concentration. These structural and optical parameters are found to be very sensitive to the thin film thickness.     

Fatigue of VT20 titanium alloy with vacuum-plasma coatings at high temperatures

We study the influence of vacuum–plasma TiN, (TiAl)N, and (TiC)N coatings on the high-cycle fatigue of VT20 titanium alloy in the temperature range 350–640°C for a loading frequency of 10 kHz. It is shown that, in this temperature range, the fatigue limits of VT20 alloy with the indicated coatings 6 μm in thickness become 15–25% higher than for the material without coating. The possibility of replacement of steel blades with titanium blades with vacuum-plasma coatings is demonstrated. Translated from Problemy Prochnosti, No. 4, pp. 101–107, July–August, 2009.     

Differential laser trigonometry for measuring the oil film thickness on water

A differential laser trigonometry method is presented for measurement of the oil film thickness on a water surface. The thickness of an oil film can be obtained with two off-plane displacements to a benchmark plane obtained by the imaging spot displacement and the configuration parameter of the imaging system subtracted. The method has been tested in the laboratory via the examination of diesel oil and petroleum films. An experimental system setup has been developed, by which the maximum measurable thickness is 12?mm and the average measurement error is 6.05?µm. The results show that the method presented is feasible, and applicable to dynamic online measurement of oil film thickness of oil spills on the sea surface.