Structural, optical and morphological studies on laser ablated nanostructured WO3 thin films

Abstract Thin films of tungsten trioxide (WO 3 ) are prepared by reactive pulsed laser deposition (PLD) technique on glass substrates at three different substrate temperatures ( T s ). The structural, morphological and optical properties of the deposited films are systematically studied using X-ray diffraction (XRD), grazing incidence X-ray diffraction (GIXRD), micro-Raman spectroscopy, scanning electron microscopy (SEM), atomic force microscopy (AFM) and UV-VIS spectrophotometry techniques. X-ray diffraction analysis reveals that crystalline WO 3 films can grow effectively even at 300 K at an oxygen pressure of 0.12 mbar. All the films deposited at various T s exhibit mixed oxide phase consisting of orthorhombic and triclinic phase of tungsten oxide with a preferred orientation along (0 0 1) lattice plane reflection. Micro-Raman results are consistent with X-ray diffraction findings. The SEM analysis shows that deposited films are porous and crystalline grains are of nano-metric dimension. The effect of T s on mean surface roughness studied by AFM analysis reveals that mean surface roughness decreases with increase in T s . The optical response of WO 3 layers measured using UV-VIS spectrophotometry is used to extract the optical constants such as refractive index ( n ), extinction coefficient ( k ) and optical band gap ( E g ), following the method of Swanepoel.