Nanostructured cauliflowers patterning in Zr doped tungsten oxide thin films grown by AACVD

Abstract

The effort is made to grow the cellular segmentation patterning of undoped and Zr doped Tungsten Oxide (ZWO) coatings engineered by aerosol assisted Chemical Vapor Deposition (AACVD) onto silica glass at 400 °C. Nanostructured cauliflowers were successfully grown without using any particular template via the chemical route of AACVD for undoped and Zr doped Tungsten Oxide. The tailored coatings of nano cauliflowers were explored by employing FE-Scanning electron microscopy/Energy Dispersive X-ray spectroscopy (FE-SEM/EDX), X-ray photoelectron spectroscopy (XPS), X-ray diffractometry (XRD), Fourier transformation Infrared spectroscopy (FTIR), UV-VIS spectroscopy (UV-VIS) and four-point probe method to study surface morphological, chemical composition, optical and electrical properties systematically. Morphological features present fractal-type cauliflower patterning because of Zr incorporation. XRD spectra revealed a monoclinic (WO3) phase in undoped Tungsten Oxide with preferential orientation (0 2 0) whereas Zr doping triggered the growth of Magneli suboxide W5O14 with tetragonal (0 0 1) preferred reflection. Adding Zr dopant caused a slight expansion of lattice with a decrease in crystallite size (54–18) nm. Vibrational information exhibits shoulder at around 854.30 cm−1, attributed to O–W–O bond shifting. Undoped and Zr doped Tungsten oxide thin film signatures positioned at 446.65 cm-1, 692 cm-1, and 854.30 cm-1 are witnessed with a red and blue shift in all rest of the Zr doped thin films. The mismatch of W and Zr ions in ionic radii, electronegativity, and thermal coefficients promote stresses leading to the variation in lattice parameters, bond length, and crystallite size with stretching of IR modes attributed to the incorporation of Zr into the host lattice sites of Tungsten oxide. XPS deconvoluted peaks yield the analysis for bond energy of O1s electrons located around 505.19 eV and 510.85 eV characterized as metallic oxide of Tungsten (WO3). UV-VIS spectroscopy presented a highly absorptive nature of coatings in the spectral range between (300–900) nm with the widening of both direct (1.9–3.2) eV and indirect (1.9–2.6) eV band gap which is of absolute interest for both fundamental and applied aspects. Transport properties unveiled the decrease of electrical resistivity of order from 106 Ω-cm (undoped) to 105 Ω-cm (Zr doped), attributed to grown high angle nanoparticles boundaries of tungsten oxide contribute to governing of nano cauliflowers and, as a result, the volume of the grain boundaries increases. The interplay between crystalline quality, tuned architecture, and oxygen vacancies can contribute to the understanding of morphological, optical, and transport properties.