Single reactor deposition of silicon/tungsten oxide core–shell heterostructure nanowires with controllable structure and optical properties

Abstract

We report a controllable growth of silicon/tungsten oxide (Si/WO 3 ) core-shell heterostructure nanowires via a two-step route using a home-built plasma-assisted hot-wire chemical vapour deposition reactor. Uniform coating of WO 3 shell indicates a clear preferential for growth on the single crystalline Si nanowires. Structure and crystallinity of the WO 3 shell are strongly dependent on the filament temperature (T f ). X-ray diffraction patterns and micro-Raman spectra suggested that there was a structure evolution from amorphous into crystallite WO 3 monoclinic structure when T f was increased to 1300 o C and above. The WO 3 shell exhibits stoichiometric tungsten trioxide structure as identified by micro-Raman and X-ray photoemission spectra analyses, which showed only W 6+ -O vibration modes for the former analysis and W 6+ energy band for the latter. Microstructure, crystal lattice, interface and growth orientation of the core-shell nanowires were recognized using a high resolution transmission electron microscopy. Our results showed that the core-shell nanowires had preserved the optical transmittance of Si core at a longer wavelength, while showing an additional transmission band edge at a shorter wavelength due to tungsten oxide coating. Their optical absorption increased to 80% and above in visible region, owing to the one-dimensional Si NWs backbone. Optical band gap of the core-shell nanowires showed a variation from 2.4 to 1.8 eV with T f . This superior visible light absorption core-shell nanowires architecture subsequently enhanced the photocurrent density of the crystalline WO 3 nanostructures.

Advanced developments in nonstoichiometric tungsten oxides for electrochromic applications

“…Open According to the relevant reaction media, the techniques can be grouped into two main categories: gas-phase technologies and Wet-chemical synthesis methods. Gas-phase technology is classified as, plasma sputtering, 190 chemical vapor depositions, 191 physical vapor depositions. Wet-chemical synthesis is, Langmuir-Blodgett, 192 electrophoretic depositions, 193 electrospinning, 194 hydrothermal, 195 and solvothermal.…”

Boosting the Performance of WO3/n‐Si Heterostructures for Photoelectrochemical Water Splitting: from the Role of Si to Interface Engineering

“…To further improve the PEC performance of such photoelectrodes, light harvesting and surface reactions can be enhanced through nano-or micro-structuring, in the form of nanowire (NW) or micro-pillar structures, coated with metal oxide films [6,15,[22][23][24][25][26][27][28] . TiO2/NWs Si showed a 2.5 times higher photocurrent density than planar TiO2/Si [6] .…”

Tungsten oxide thin film for room temperature nitrogen dioxide gas sensing

“…There is a growing demand of metal oxide thin films for numerous important technological applications such as gas sensing, solar cells, solar absorbers, etc. The fast-growing industries and increase in exhaust emissions of gases from industries has put a large demand on the sensitive and selective detection of hazardous gases for environmental pollution monitoring, process control and safety for human health [1,2,3]. This has attributed to the fabrication of gas sensor devices [1,2,3,4,5].…”

“…The fast-growing industries and increase in exhaust emissions of gases from industries has put a large demand on the sensitive and selective detection of hazardous gases for environmental pollution monitoring, process control and safety for human health [1,2,3]. This has attributed to the fabrication of gas sensor devices [1,2,3,4,5]. NO2 is one of the most potentially toxic gas which can lead to respiratory problems to humans.…”

“…Various attempt to reduce the operating temperature of WO3 nanostructures based sensors such as WO3 combine with other materials to form heterostructures or composite sensors have been performed [1,12]. Tungsten oxide (WO3) is an n-type metal oxide semiconducting material with a band gap of about 2.7 eV [3]. WO3 is considered to be a highly promising material for a broad range of applications such as in electronic devices, super-capacitors, optical aspects, gas sensors, solar energy, photocatalyst and biosensors [4,5,6,14,15,16,17].…”