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This study explores the surface characteristics evaluation and performance optimization of tungsten (W)-doped vanadium dioxide (VO2) thin films. W-doped vanadium dioxide films were deposited on B270 glass substrates using an electron beam evaporation technique combined with the ion beam-assisted deposition (IAD) method. The Taguchi method was used to analyze the performance optimization of VO2 thin films, and L16 orthogonal array design and Minitab software were used for optimization calculations. The surface roughness, visible light transmittance, infrared transmittance, and residual stress of un-doped and tungsten-doped (3–5%) VO2 thin films are set as the quality performance indicators of thin films. The goal is to identify the key factors that affect the performance of VO2 thin films during deposition and optimize their process parameters. The experimental results showed that a VO2 thin film with 3% tungsten doping, an oxygen flow rate of 60 sccm, a heating temperature of 280 °C, and a film thickness of 60 nm exhibited the lowest surface roughness of 2.12 nm. A VO2 thin film with 5% tungsten doping, an oxygen flow rate of 0 sccm, a heating temperature of 280 °C, and a film thickness of 60 nm had the highest visible light transmittance at 64.33%. When the oxygen flow rate was 60 sccm, the heating temperature was 295 °C, the film thickness was 150 nm, and the tungsten doping was 5%, the VO2 thin film showed the lowest infrared transmittance of 31.34%. A thin film with 5% tungsten doping, an oxygen flow rate of 20 sccm, a heating temperature of 265 °C, and a film thickness of 120 nm exhibited the lowest residual stress of −0.195 GPa. [ABSTRACT FROM AUTHOR]

The undoped and tungsten (W)-doped vanadium dioxide (VO2) thin films were prepared by electron beam evaporation associated with ion-beam-assisted deposition (IAD). The influence of different W-doped contents (3–5%) on the electrical, optical, structural, and thermo-mechanical properties of VO2 thin films was investigated experimentally. Spectral transmittance results showed that with the increase in W-doped contents, the transmittance in the visible light range (400–750 nm) decreases from 60.2% to 53.9%, and the transmittance in the infrared wavelength range (2.5 μm to 5.5 μm) drops from 55.8% to 15.4%. As the W-doped content increases, the residual stress in the VO2 thin film decreases from −0.276 GPa to −0.238 GPa, but the surface roughness increases. For temperature-dependent spectroscopic measurements, heating the VO2 thin films from 30 °C to 100 °C showed the most significant change in transmittance for the 5% W-doped VO2 thin film. When the heating temperature exceeds 55 °C, the optical transmittance drops significantly, and the visible light transmittance drops by about 11%. Finally, X-ray diffraction (XRD) and scanning electron microscope (SEM) were used to evaluate the microstructure characteristics of VO2 thin films. [ABSTRACT FROM AUTHOR]

We propose two single-wavelength notch filters and one dual-wavelength (480 and 620 nm) notch filter to enhance image contrast. The stack structure of the notch filters was designed as (Ta2O5/SiO2)4Ta2O5 in Essential Macleod thin film simulation software. Dual-electron-beam evaporation with ion beam-assisted deposition was used to prepare optical interference filters with different center wavelengths. A multilayer notch filter with a center wavelength of 620 nm was deposited on the front surface of the glass, and then a notch filter with a center wavelength of 480 nm was coated on the rear surface of the same glass. The proposed dual-wavelength (480 and 620 nm) notch filter is a combination of two single-wavelength notch filters coated on a double-sided glass substrate to compensate for residual stress. The transmittance, residual stress, and surface roughness of the proposed notch filter were evaluated using different measuring instruments. The experimental results show that the residual stress of the dual-wavelength notch filter could be reduced to 10.8 MPa by using a double-sided coating technique. The root-mean-square (RMS) surface roughness of the notch filters was measured by using a Linnik microscopic interferometer. The RMS surface roughness was 1.80 for the 620 nm notch filter and 2.09 for the 480 nm notch filter. The image contrast obtained with the three different notch filters was measured using an optical microscope and a CMOS camera. The contrast value could be increased from 0.328 (without a filter) to 0.696 (dual-wavelength notch filter). [ABSTRACT FROM AUTHOR]

This study presents the effect of oxygen flow rate on the optical, electrical, and mechanical properties of indium tin oxide (ITO) thin films prepared by the DC magnetron sputtering technique. The oxygen flow rate was varied from 10 to 50 sccm. The ITO thin films deposition under different oxygen flow rates exhibits different properties. We used an optical spectrometer to measure the optical transmittance and a four-point probe instrument to determine the resistivity. A home-made Twyman-Green interferometer was used to evaluate residual stress and a microscopic interferometer was used to measure the surface roughness of ITO thin films. The experimental results show that the average optical transmittance is larger than 85% in visible range; the electrical resistivity has a minimum 6.85×10-4 ohm-cm for the oxygen flow of 10 sccm. The residual stress is varied from −0.15 GPa to −0.34 GPa in the range of 10–50 sccm. The root-mean-square (rms) surface roughness is changed from 2.64 nm to 2.74 nm as the oxygen flow rate increases. The results show that the oxygen flow rate has significant influence on the electrical resistivity, residual stress, and surface roughness of the ITO thin film. [ABSTRACT FROM AUTHOR]

We present the influences of radio-frequency (RF) power on the optical, electrical, mechanical, and structural properties of Ga-doped zinc oxide (GZO) thin films by RF magnetron sputtering at room temperature. GZO thin films were grown on unheated glass and silicon substrates using radio-frequency (RF) magnetron sputtering method with different RF powers (from 60 W to 160 W). The optical properties of the GZO thin film were determined by a UV–vis spectrophotometer. The residual stress in GZO films were measured by a home-made Twyman–Green interferometer with the fast Fourier transform (FFT) method. The surface roughness of GZO films were measured by a microscopic interferometry. The microstructure, composition and crystal orientation of the GZO films were determined by scanning electron microscope (SEM), energy dispersive X-ray spectroscopy (EDS), and X-ray diffraction (XRD). This paper revealed that the optical, electrical, mechanical, and structural properties of GZO thin film are subject to the RF power. For the optical spectrum measurement, an average optical transmittance in the visible region of the spectra of 85% was obtained. For the characteristic measurements, all the GZO thin films deposited by RF magnetron sputtering have compressive stress at different RF powers. A minimum residual stress of 0.24 GPa is found at the RF power of 140 W. A four-point probe method was used to measure the resistivity of the GZO thin films with different powers, the results indicate that the resistivity increases with increasing of RF power. In addition, the root-mean-square (RMS) surface roughness of GZO thin films slightly increases as the RF power is increasing. We have also compared the results with the relevant literatures. [ABSTRACT FROM AUTHOR]

The NiFe thin films were prepared at room temperature by DC sputtering technique from a NiFe target onto silicon wafer, NBK7 and STIM35 glass substrates. The optimal deposition condition of NiFe thin films was obtained to be used for high density magnetic recording applications. The film thickness was determined by the SEM measurement. The electrical resistivity of the NiFe thin film with a thickness of 240 nm was \(1.17 \times 10^{{-5}}\Omega \) -cm. The average residual stress and thermo-mechanical parameters were determined by the fast Fourier transform (FFT) method. The average residual stresses on two different substrates are −50 ± 2 MPa. The residual stress versus substrate temperature relation is a linear correlation after heating from room temperature to 100 °C. A double substrate technique was used to determine the thermal expansion coefficients and biaxial modulus of the NiFe thin films. The experimental results show that the thermal expansion coefficient of the NiFe thin films is \(6.44 \times 10^{-6}\,~^{\circ}{\rm C}^{-1}\) . The biaxial modulus is 779 GPa. The surface roughness was evaluated by using a microscopic interferometer. The root-mean-square roughness of the NiFe thin films were 1.350 nm for NBK7, 1.403 nm for STIM35 and 1.387 nm for silicon wafer. [ABSTRACT FROM PUBLISHER]

Abstract: The effect of sputtering anisotropic ejection on the optical properties and internal stress of niobium pentoxide (Nb2O5) films prepared by ion-beam sputtering deposition (IBSD) was investigated experimentally. Thin films were deposited on unheated BK7 glass substrates and silicon wafers at different ejection angles surrounding a metal target. The ejection angles varied from 0° to 75° in increments of 15° for each substrate. It was found that the optical constants of the Nb2O5 films were significantly influenced by the sputtering ejection angle. The surface roughness and residual stress in the Nb2O5 thin films were also found to vary with the ejection angle. In this work, Nb2O5 films had a higher refractive index, lower absorption, lower stress and lower roughness when films deposited at an ejection angle of 30°. [ABSTRACT FROM AUTHOR]

Abstract: The residual stresses, surface roughness and microstructure in titanium oxide films prepared by electron-beam evaporation and deposited with different geometries were investigated, with particular focus on the in-plane anisotropy of the biaxial stresses and microstructures. Thin films were deposited with various deposition angles on B270 glass substrates and silicon wafers. Two different types of deposition geometries were studied. The residual stress in the thin films was examined by a phase-shifting Twyman-Green interferometer. The optical constants, biaxial stress and surface roughness were found to be related to the evolution of the anisotropic microstructures in the films. The results revealed that the anisotropic stresses that developed in the evaporated titanium oxide films were dependent upon the deposition geometry and microstructure of the films. [Copyright &y& Elsevier]

Abstract: The measurement of surface roughness of optical thin films based on fast Fourier transform (FFT) associated with a Gaussian filter was presented. The measurement of the surface roughness is performed by a Fizeau-type microscopic interferometer combined with the Matlab program to analyse the captured interferograms. The surface profile can be obtained by the fringe pattern analysis program using FFT method. In order to improve the accuracy, we normalize the fringe pattern to eliminate the background variation before using the FFT. The roughness profile is filtered by the Gaussian filter after the phase change is converted to surface height distribution. The root-mean-square value of surface roughness of optical thin films was determined by our proposed method. The results were verified by atomic force microscopy (AFM). [Copyright &y& Elsevier]

This study presents a multilayer design and fabrication of an optical notch filter for enhancing visual quality. A cost-effective multilayer design of notch filter with low surface roughness and low residual stress is proposed. A 9-layer notch filter composed of SiO2 and Nb2O5 with a central wavelength of 480 nm is prepared by electron beam evaporation combined with ion-assisted deposition. The optical transmittance, residual stress, and surface morphology are measured by a UV/VIS/NIR spectrophotometer, Twyman-Green interferometer and field emission scanning electron microscopy (FE-SEM). The transmittance of the notch filter at the central wavelength is above 15%, and the average transmittance of the transmission band is about 80%. The residual stress of the notch filter is −0.235 GPa, and the root mean square surface roughness is 1.85 nm. For improving the visual quality, a good image contrast can be obtained by observing the microscopic image using the proposed notch filter. [ABSTRACT FROM AUTHOR]

We present a new laser protective lens based on a multilayered notch filter design with low residual stress and low surface roughness. An18-layer notch filter was prepared by electron beam evaporation with an ion-assisted deposition technique, which was composed of SiO2 and Nb2O5 with a center wavelength of 532 nm. The optical transmittance, residual stress, surface roughness, and surface morphology were measured by a UV/VIS/NIR spectrophotometer, Twyman–Green interferometer, scanning probe microscope, Linnik microscopic interferometer, and field-emission scanning electron microscopy (FE-SEM). The transmittance of the notch filters at center wavelength is 0.2%, and the average transmittance of the transmission band is about 70%. The residual stress of the notch filter is −0.298 GPa, and the root mean square surface roughness is 1.88 nm. The experimental results show that the optical transmittance meets the design requirements. [ABSTRACT FROM AUTHOR]