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Amorphous vanadium pentoxide (major phase) thin films of various thicknesses were grown on the substrates that possessed low (aluminized quartz) and high (quartz) infrared (IR) emittance property utilizing radio frequency (RF) magnetron sputtering technique. Microstructural characterizations are carried out by several techniques such as noncontact optical profilometry, energy dispersive X‐ray (EDX) spectroscopy, X‐ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), and X‐ray diffraction (XRD). The as‐grown amorphous films show stoichiometric vanadium oxide, where vanadium is in V5+ as a major proportion compared with V4+ states. Thermo‐optical properties, namely, solar transmittance (τs), reflectance (ρs), absorptance (αs) and IR emittance (εir) along with optical constant, for example, optical band gap, are evaluated. A modified Urbach equation was used to simulate the optical absorption data to understand the presence optical absorption below the band edge. [ABSTRACT FROM AUTHOR]

Molybdenum doped vanadium oxide film on quartz and silicon substrates are grown by pulsed RF magnetron sputtering method. Surface morphology, phase analysis and oxide states are investigated by field emission scanning electron microscopy, X-ray diffraction and X-ray photoelectron spectroscopy techniques, respectively. Crystalline nature of the film deposited on both quartz and silicon are depicted. The transmittance and reflectance spectra recorded for the entire solar region. Further, optical constants viz. optical band gap and refractive index of the deposited films are estimated. Wavelength dependent low reflectance characteristic is observed for the deposited film on silicon. IR emittance (εIR) and sheet resistance (Rs) of the film are also evaluated. Copyright © 2017 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Vanadium oxide films, deposited on aluminium (Al), titanium (Ti) and tantalum (Ta) metal substrates by pulsed RF magnetron sputtering at a working pressure of 1.5 x10−2 mbar at room temperature are found to display mixed crystalline vanadium oxide phases viz., VO2, V2O3, V2O5. The films have been characterized by field-emission scanning electron microscopy, X-ray diffraction, differential scanning calorimetry (DSC) and X-ray photoelectron spectroscopy, and their thermo-optical and electrical properties have been investigated. Studies of the deposited films by DSC have revealed a reversible-phase transition found in the temperature range of 45–49 °C. [ABSTRACT FROM AUTHOR]

Vanadium oxide thin films on silicon (Si) substrate are grown by pulsed radio frequency (RF) magnetron sputtering technique at RF power in the range of 100–700 W at room temperature. Deposited thin films are characterized by field emission scanning electron microscopy (FESEM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) techniques to investigate microstructural, phase, electronic structure and oxide state characteristics. The reflectance and transmittance spectra of the films and the Si substrate are recorded at the solar region (200–2300 nm) of the spectral window. Substantial reduction in reflectance and increase in transmittance is observed for the films grown beyond 200 W. Further, optical constants viz. absorption coefficient, refractive index and extinction coefficient of the deposited vanadium oxide films are evaluated. [ABSTRACT FROM AUTHOR]

Germanium coated black polyimide (GBP) is often used as passive thermal control element for sunshield membrane of satellite antenna. However, GBP degrades fast while there is no protective coating applied. The present work is aimed towards the development of protective films which could hinder the degradation of GBP. At the same time, the basic characteristic of GBP membrane that is RF transparency should not be trade off. Here, RF transparent and protective vanadium oxide (VO) and vanadium oxide/silicon dioxide (VO/SO) thin films are developed by RF magnetron sputtering technique on GBP at a constant 400 W. Field emission scanning electron microscopy (FESEM) and X-ray photoelectron spectroscopy (XPS) techniques are utilized to investigate microstructural and oxide characteristics, respectively. Thermo-optical properties such as, solar absorptance (α s ) and IR emittance (ε ir ) are also evaluated. Introduction of SiO 2 layer over vanadium oxide layer leads to decrease in α s to about 12%. RF losses e.g. insertion loss and return loss are measured in Ka band (27–39 GHz) and they found to be RF transparent characteristic. Thermal stability of the oxide films are also studied by differential scanning calorimetry (DSC) technique. [ABSTRACT FROM AUTHOR]

ITO/Ag/ITO (IAI) multilayer coatings were designed for spectral beam splitter applications and these coatings were deposited on glass substrates by magnetron sputtering method. The thicknesses of the component layers, namely, Ag and ITO were varied to achieve high visible transmittance, high NIR-IR reflectance and optimum cut-off wavelength. The optimized ITO/Ag/ITO exhibits high visible transmittance (∼88%) and high NIR-IR reflectance (>90%) with an optimum cut-off wavelength (∼900 nm). A novel chemical etching method was used to improve the transmittance of the plain glass substrate. The optimized IAI multilayer coating deposited on single side etched glass substrate resulted in increase in transmittance (∼91%), which is due to the nano-porous morphology of the etched glass substrate. The angular and polarization dependence studies of IAI multilayer coatings were also studied in detail. [ABSTRACT FROM AUTHOR]

ITO thin films were deposited on flexible fluorinated ethylene propylene (FEP) substrates by pulsed direct current reactive magnetron sputtering system using an In:Sn (90%–10% wt.) alloy target. The influence of the deposition parameters (argon and oxygen flow rates, and substrate temperature) and effect of coating thickness on the optical, electrical, structural and microstructural properties of ITO thin films deposited on FEP was investigated. The thickness of the ITO coatings was varied from 5 to 180 nm. The optimized ITO coating (10 nm thick) exhibited high IR emittance (79%) on FEP substrate with high average solar transmittance (94.0%) and moderate sheet resistance (3 kΩ/sq.). We also investigated in detail the angular dependence of reflectance as well as haze factor of thin ITO coatings. Our results suggest that 10 nm thick ITO coating exhibits an average haze factor of 8.6%. The high value of IR emittance, moderate sheet resistance and high solar transmittance along with low haze factor indicate the suitability of ITO thin films on FEP substrates as flexible optical solar reflector for space applications. [ABSTRACT FROM AUTHOR]

Vanadium pentoxide (V 2 O 5 ) coatings on quartz and Si(111) substrates are grown by pulsed RF magnetron sputtering technique at constant RF power of 700 W at room temperature. Phase, microstructure and surface morphology are investigated by X-ray diffraction, field emission scanning electron microscopy and atomic force microscopy techniques, respectively. The transmittance and reflectance spectra are recorded for the solar region (200–2300 nm) of the spectral window. Further, optical constants viz. optical band gap, refractive index and extinction coefficient of the deposited V 2 O 5 coatings are estimated. Thickness dependent optical band gaps are found in the range of 2.78–2.59 eV. Wavelength dependent characteristic is also observed both for refractive index and extinction coefficient. Finally, thickness of the present coating predicted theoretically which is matched well with the thickness measured by direct measurement e.g., nanoprofilometry technique. [ABSTRACT FROM AUTHOR]

We report nanoindentation response of indium tin oxide (ITO) film deposited by reactive direct current (DC) magnetron sputtering. The phase pure ITO film showed dense and needle-like nanostructure. Detailed mechanical characterization of ITO film was carried out by the nanoindentation technique. The average nanohardness and elastic modulus were evaluated as about 17.5 GPa and 189 GPa, respectively. Comparatively higher nanohardness and modulus values were found in the present work, which is possibly linked with the dense nanostructure of the ITO film. Further, fracture toughness was measured as ~0.56 MPa m 0.5 . The corresponding projected area of indentation, elastic energy and plastic energy were also reported. [ABSTRACT FROM AUTHOR]

Abstract: Alumina thin films were deposited on SS304 and Ti metal substrates using a pulsed rf magnetron sputtering technique at different radio frequency (rf) powers corresponding to input powers of 300, 500 and 700W. Both direct and reactive sputtering methods were employed to deposit the alumina films. The deposited films were thoroughly characterized by X-ray photoelectron spectroscopy (XPS) to investigate electronic structure and stoichiometry. Further, the effect of different rf powers, role of substrates and effect of deposition methods e.g. direct and reactive sputtering on binding energy, atomic concentration ratio (e.g., oxygen to aluminium ratio, O/Al) and related properties have been studied extensively by XPS. The results suggested that the reactive sputtering method could provide alumina thin films with the chemical composition that matches with the stoichiometric one. Further, the film deposition process by reactive sputtering was not a sensitive function of the variations in the input power. [Copyright &y& Elsevier]

Abstract: Alumina thin films were deposited on titanium (Ti) and fused quartz by both direct and reactive pulsed rf magnetron sputtering techniques. X-ray diffraction, field emission scanning electron microscopy, energy dispersive X-ray spectroscopy and atomic force microscopy were utilized to study the phases and surface morphology of the films. The as-deposited alumina thin films were amorphous. However, after annealing at 500°C in vacuum, the crystalline peaks corresponding to the Theta (θ), Delta (δ) and Chi (χ) alumina phases were obtained. The optical transmittance and reflectance as well as IR emittance data were also evaluated for the thin films. The transmittance, e.g., (~90%) of the bare quartz substrate was not changed even when the alumina thin films were deposited for an hour. However, further increase in deposition time (e.g., 7h) of the alumina thin films showed only a marginal decrease (e.g., ~5%) in average transmittance of the bare quartz substrate. The direct and indirect optical band gaps and extinction coefficient of the alumina films were estimated from the transmittance spectra. The IR emittance of the Ti substrate (e.g., ~16%) was almost constant after depositing alumina thin films for an hour. Further increase in deposition time showed only a marginal increase (e.g., ~9%) in IR emittance value. Therefore, it is proposed that the alumina films developed in the present work can act as a protective cover for the Ti substrate while retaining the thermo-optical properties of the same. The nanohardness and Young׳s modulus of the alumina thin films were evaluated by the novel nanoindentation technique. The nanohardness was measured as ~6GPa. Further, Young׳s modulus was evaluated as ~116GPa. The magnitudes of the nanomechanical properties of the thin films were a little smaller than those reported in the literature. This was linked to the lack of crystalline phases in the as-deposited alumina thin films. [Copyright &y& Elsevier]

Abstract: Silica (SiO2) mono-layer and silica–alumina (SiO2–Al2O3) bi-layer thin films were developed on both SS304 and Ti thin foils by pulsed rf magnetron sputtering. The solar absorptance (α s) and IR emittance (ε ir) of the films were measured. Both α s and ε ir of SS304 and Ti were increased after depositing SiO2 and SiO2–Al2O3 bi-layer thin film. The ratio of solar absorptance and IR emittance (i.e. α s/ε ir) can be tailored in a large range e.g. 3.3–0.850 for SS and 3.66–1.085 for Ti which is useful for many spacecraft subsystems to tailor their operating temperatures. Further, the microstructure, surface morphology and topography of the films were investigated by field emission scanning electron microscopy, energy dispersive X-ray spectroscopy and atomic force microscopy. [Copyright &y& Elsevier]