Influence of C2H2 Flow Rates on Optical Properties, Surface Roughness, and Residual Stress of Ti/WC Thin Films Deposited on Glass Substrates

This paper investigates the influence of C₂H₂ flow rates on the optical properties, surface roughness, and residual stress of Ti/WC thin films deposited on glass substrates. A range of Ti/WC thin films with varying carbon contents were prepared using the reactive pulsed DC magnetron sputtering technique. The properties of the Ti/WC films can be tuned by adjusting the deposition parameters, among which the acetylene (C₂H₂) flow rate plays a key role in determining the thin film's microstructure, optical properties, and stress behavior. The optical properties of the thin films were analyzed using UV-visible-NIR spectroscopy and Fourier transform infrared (FTIR) spectroscopy, the surface morphology was analyzed using microscopic interferometry, and the residual stress in the films was measured using a homemade Twyman-Green interferometer. The measurement results show that the average reflectance of Ti/WC films decreases with the increase in the C₂H₂ flow rate, and the measured value changes from 52.24% to 44.56% in the wavelength of 400-800 nm. The infrared reflectance of Ti/WC films in the wavelength of 2.5-25 μm is 81.8% for 10 sccm, 80.8% for 20 sccm, 77.2% for 30 sccm, and 73.6% for 40 sccm. The tensile stress of the Ti/WC films deposited on B270 substrates increases with the increase in the C₂H₂ flow rate, and the stress value changes from 0.361 GPa to 0.405 GPa. The surface roughness of Ti/WC films initially increases and then decreases slightly with the increase in the C₂H₂ flow rate. These results indicate that the C₂H₂ flow ratio significantly affects the reflectance in the visible and infrared bands, surface roughness, and residual stress of the Ti/WC films, which is of great significance for optimizing thin film performance to meet specific application requirements.