Plasma parameters, structural and optical properties of Au-doped MoO 3 thin films prepared by DC magnetron sputtering

MoO3 and Au–MoO3 thin films were prepared on glass substrates by DC magnetron sputtering. The effect of sputtering power, substrate temperature, and Au doping on their structure and optical properties was studied and analyzed. The film thickness increased with sputtering power and Au content, reaching 353 nm at the highest doping. XRD showed that the as-deposited films were amorphous but crystallized into the orthorhombic α-MoO3 phase after annealing. The crystallite size became larger at higher power, while Au doping produced an extra Au (111) peak and reduced the size due to lattice strain. Optical results showed that the transmittance decreased with power but improved at higher substrate temperature. Absorbance and the absorption coefficient (α) increased with sputtering power and Au doping, confirming strong light absorption in the films. The optical band gap varied between 2.90 and 3.20 eV depending on conditions, and both the refractive index and extinction coefficient changed systematically. These results show that deposition parameters and Au doping can control the structural and optical behavior of MoO3 thin films, making them useful for optoelectronic applications