Structural, morphological and optical properties of electron beam evaporated WO3 thin films

Tungsten trioxide (WO3) is one of the best transparent metal oxides for advanced technological applications. WO3 exhibits a wide variety of novel properties, particularly in thin film form. This investigation focuses on the morphological and optical properties of WO3 thin films prepared by electron beam deposition in an oxygen partial pressure of 2 × 10−4 mbar and at various substrate temperatures. The deposited films at room temperature (RT) are amorphous, but the crystallinity is enhanced by increasing the substrate temperature with noticeable x-ray diffraction peaks at (320), (210) and (402). The peaks represent the predominantly orthorhombic phase, with a portion of the hexagonal phase being included, of the WO3 films. The surface roughness and the grain size also increased as the substrate temperature increased. The optical transmittance and energy band gaps decreased with increasing substrate temperature. The band gap energy values were from 3.302 to 3.084 eV for the films deposited at substrate temperatures ranging from RT to 450 °C.