Fabrication of selective l-glutamic acid sensor in electrochemical technique from wet-chemically prepared RuO2 doped ZnO nanoparticles

Synthesis and physical properties of Ag doped niobium pentoxide thin films for Ag–Nb2O5/Si heterojunction device

In this study, Nb2O5 ceramic was used as the target to deposit the Nb2O5 thin films on glass substrates with the radio frequency (RF) magnetron sputtering method. Different deposition temperatures and O2 ratios were used as parameters to investigate the optical properties of Nb2O5 thin films. The deposition parameters were a pressure of 5 × 10−3 Torr, a deposition power of 100 W, a deposition time of 30 min, an O2 ratio (O2/(O2 + Ar), in sccm) of 10% and 20%, and deposition temperatures of room temperature (RT), 200, 300 and 400 °C, respectively. We found that even if the deposition temperature was 400 °C, the deposited Nb2O5 thin films revealed an amorphous phase and no crystallization phase was observed. The optical properties of transmittance of Nb2O5 thin films deposited on glass substrates were determined by using a ultraviolet-visible (UV-vis) spectrophotometer (transmittance) and reflectance spectra transmittance (reflectance, refractive index, and extinction coefficient) in the light wavelength range of 250–1000 nm. When the O2 ratio was 10% and the deposition temperature increased from RT to 200 °C, the red-shift was clearly observed in the transmittance curve and the transmission ratio had no apparent change with the increasing deposition temperature. When the O2 ratio was 20%, the red-shift was not observed in the transmittance curve and the transmission ratio apparently decreased with the increasing deposition temperature. The variations in the optical band gap (Eg) values of Nb2O5 thin films were evaluated from the Tauc plot by using the quantity hν (the photon energy) on the abscissa and the quantity (αhν)r on the ordinate, where α is the optical absorption coefficient, c is the constant for direct transition, h is Planck’s constant, ν is the frequency of the incident photon, and the exponent r denotes the nature of the transition. As the O2 ratio of 10% or 20% was used as the deposition atmosphere, the measured Eg values decreased with the increase of the deposition temperature. The reflectance ratio, extinction coefficient, and refractive index curves of Nb2O5 thin films were also investigated in this study. We would show that those results were influenced by the deposition temperature and O2 ratio.

https://www.mdpi.com/2072-666X/7/9/151/pdf

Investigation of Antireflection Nb₂O₅ Thin Films by the Sputtering Method under Different Deposition Parameters.

Corrosion of thin, magnetron sputtered Nb2O5 films

The preparation of responsive multilayered structures with quarter-wave design based on layer-by-layer deposition of sol-gel derived Nb2O5 films and spin-coated MEL type zeolite is demonstrated. The refractive indices (n) and thicknesses (d) of the layers are determined using non-linear curve fitting of the measured reflectance spectra. Besides, the surface and cross-sectional features of the multilayered structures are characterized by scanning electron microscopy (SEM). The quasi-omnidirectional photonic band for the multilayered structures is predicted theoretically, and confirmed experimentally by reflectance measurements at oblique incidence with polarized light. The sensing properties of the multilayered structures toward acetone are studied by measuring transmittance spectra prior and after vapor exposure. Furthermore, the potential of the one-dimensional photonic crystals based on the multilayered structure consisting of Nb2O5 and MEL type zeolite as a chemical sensor with optical read-out is discussed.

https://www.mdpi.com/1424-8220/14/7/12207/pdf

Vapor responsive one-dimensional photonic crystals from zeolite nanoparticles and metal oxide films for optical sensing.

The optical properties of thin Nb2O5 films, obtained by spin coating of Nb sol on glass and silicon substrates are investigated. The Nb sol was prepared by a sonocatalytic method using niobium chloride dissolved in ethanol. A calculation procedure for reliable and unambiguous determination of optical constants (refractive index and extinction coefficient) and thickness of films is developed that uses transmittance and reflectance measurements and non-linear curve fitting. By means of the developed procedure, the impacts of the sol ageing and the post deposition annealing on the optical properties and thickness of the films are investigated. It is demonstrated that films with controlled thicknesses and refractive index values in the range from 1.82 to 2.20 (at wavelength of 600 nm) could be obtained using different concentrations of the Nb sol and post deposition annealing in the range 60–650 °C. The possibility of fabrication of single layer anti-reflective coating for silicon is discussed.

Optical characterization of sol–gel derived Nb2O5 thin films

Aluminum-doped zinc oxide thin films deposited by electrospray method

Influence of ZnCl2 concentration on the structural and optical properties of electrochemically deposited nanostructured ZnO

Polycrystalline ZnO thin films were prepared on silicon substrates using electrospray method with vertical setup. Water and ethanol were used as solvents for zinc acetate dehydrate and no postdeposition annealing was required for formation of ZnO. The influence of substrate temperature in the range of 150–250°C on surface morphology and roughness was studied by Scanning Electron Microscopy (SEM), Atomic Force Microscopy (AFM), and optical profilometry. An improvement of surface quality and smoothing of the films with temperature were obtained. X-ray diffraction measurements revealed that, at all investigated substrate temperatures, the films were polycrystalline with crystallites’ sizes decreasing with temperature. Besides, the preferred crystal orientation varies with the substrate temperature. The analysis of surface chemical composition and oxidation state was performed with X-ray photoelectron spectroscopy (XPS). It was shown that, at substrate temperature of 200°C, the deposited ZnO films were closest to the stoichiometric ones. In general, the films at 150°C were oxygen-deficient, while at other studied temperatures, the films had excess of oxygen more pronouncedly at 200°C. Spectral ellipsometric measurements confirmed that the structural disorder is the highest at 150°C and improves with temperature. Refractive indexes for films at 200°C and 250°C are almost the same, 1.97 and 1.93, respectively, at wavelength of 600 nm, while for the sample deposited at 150°C, the refractive index is substantially lower, 1.67. The optical band gap is slightly influenced by the substrate temperature: 3.27 eV at 150°C and 3.32 eV at 200°C.

/pdf/effect-of-substrate-temperature-on-the-microstructural-2os2ubvjz6.pdf

Effect of Substrate Temperature on the Microstructural, Morphological, and Optical Properties of Electrosprayed ZnO Thin Films

One dimensional photonic crystal (1D-PhC) in form of 19 layered stack was prepared through layer-by-layer deposition of spin coated Poly (methyl methacrylate) (n = 1.49 at 1.55 ?m) and vacuum deposited As2S3 (n = 2.27 at 1.55 ?m) as low and high refractive index materials, respectively. The optical properties of the single layers and the multilayered stack are studied at normal and oblique incidence of linearly polarized light. The possibility of using the 1D-PhC as an omnidirectional reflector was exploited theoretically and confirmed experimentally. Besides, the prospect of using the studied structure for chemical sensing with optical read-out is demonstrated.

Georgi Marinov

Papers

Optical characterization of sol–gel derived Nb2O5 thin films

Aluminum-doped zinc oxide thin films deposited by electrospray method

Influence of ZnCl2 concentration on the structural and optical properties of electrochemically deposited nanostructured ZnO

Effect of Substrate Temperature on the Microstructural, Morphological, and Optical Properties of Electrosprayed ZnO Thin Films

One dimensional photonic crystals from As 2 S 3 and PMMA films for photonic and sensor applications