Investigation of gasochromic properties in tungsten oxide thin films prepared by glancing angle deposition using electron beam evaporation

Tungsten oxide (WO₃) thin films were fabricated using a combination of electron beam evaporation and glancing angle deposition (GLAD) to study their gasochromic properties. The influence of deposition angle ( α between 0° and 88°) and post-process annealing on the morphology, crystallinity, and optical response to hydrogen was systematically analyzed. Structural characterization revealed that GLAD promotes the formation of inclined fibrous columns with enhanced porosity due to self-shadowing effects. Quantitative analysis combining SEM and optical modeling confirmed that porosity and refractive index correlate strongly with deposition angle. Gasochromic measurements showed that nanocrystalline films had better optical response and faster response times ( ∼ 5 min ) to hydrogen than amorphous films ( ∼ 11 min ). However, the gasochromic response decreased with an increasing deposition angle, which correlated with a reduced optical path length. The tunable morphology and refractive index achieved by GLAD highlight its potential for designing multifunctional optical coatings that combine hydrogen sensitivity with tailored optical performance.