Nanostructured Tungsten Oxide Thin Films Deposited By Glancing Angle Magnetron Sputtering

Tungsten trioxide?WO₃?is a kind of transition metal oxide,which has wide application prospects in electrochromic devices,gas sensors,photocatalysts and other fields.Because WO₃ thin films have high transmittance change,good reversibility,low relative price,long life and non-toxic,it is the electrochromic material that be used earliest and the most widely than other electrochromic materials.It can be applied to buildings and cars on the glass,to fabricate intelligent window which can adjust light,conserve energy and control of heat load.However,there are many defects in the response time,discoloration efficiency and cycle life and other aspects which restricts practical application of tungsten trioxide material.In this study,nanostructured WO₃ thin films were fabricated on different substrates by DC glancing angle magnetron sputtering and pulsed power glancing angle magnetron sputtering.The effects of different process parameters on the surface morphology,microstructure,transmittance and electrochromic properties of the thin films were characterized by XRD,SEM and other analytical methods.The main contents of this paper are as follows:?1?The effects of oxygen partial pressure on the morphology,structure and transmittance of WO₃ thin films are studied.When using DC power and pulsed power,the argon / oxygen ratio is 3: 2(P_Ar:P_O2= 0.3 Pa:0.2 Pa)and 2: 3(P_Ar:P_O2= 0.2 Pa:0.3 Pa),respectively.?2?The effects of the oblique angle of incident particle flow on the morphology,structure and transmittance of nanostructured WO₃ thin films are investigated.When the glancing angle is more than 60°,WO₃ thin films with nanometer oblique columnar structure are obtained.With the increase of the glancing angle,the nanostructure obviously and the specific surface area increases.?3?Influence of heat treatment on crystal structure and morphology of WO₃ thin films.The WO₃ thin films deposited by glancing angle magnetron sputtering at room temperature are amorphous,after annealing at 450 ?,the thin films are transformed into a monoclinic crystal structure.The nano-columnar disappears and the nanostructures are interconnected by thermal diffusion,nano-porous structure is formed.?4?The maximum power and substrate heating maximum voltage of the pulse power are optimizationing when WO₃ thin films are deposited on ITO / PET flexible substrates.Optimizationing the maximum sputtering power is 90 W and the maximum substrate heating voltage is 50 V.?5?The colouring and fading response time of nanostructured WO₃ thin films is 10 s and 2 s,respectively,Which is 17 s and 6 s for dense WO₃ thin films,respectively.When the wavelength range is 500-600 nm,the change in luminous flux density of them is 66.42 percent and 36.80 percent,respectively.So,the electrochromic properties of nanostructured WO₃ thin films fabricated by glancing angle magnetron sputtering are better than that of dense WO₃ thin films prepared by conventional magnetron sputtering.