Microstructure and stress evolution of W nanofilms prepared by arc ion plating under different deposition time and substrate bias

Abstract

This study investigates the effects of film thickness and substrate bias on the microstructure and stress state of tungsten (W) films prepared by arc ion plating (AIP) on substrates including 304 stainless steel (SS), tungsten (W), and Si (100). The microstructure of the films was characterized using X-ray diffraction (XRD) and field emission scanning electron microscopy (FE-SEM). Residual stress was analyzed using substrate curvature techniques combined with Stoney's formula and Huseh's formula. The results indicate that the W films are single-phase, predominantly comprising the pure α-phase. The film surfaces are dense and smooth, with the absence of large particles. The films consist of closely packed columnar grains, and no microcracks, voids, or delamination were observed at the film-substrate interface, indicating strong adhesion. As the film thickness increased, the curvature of the W/SS system and the compressive stress in the film both increased, which closely matched the fitted curves. As the substrate bias increased, the curvature of the W/SS system decreased, and the compressive stress in the W film increased. At higher substrate biases, deposition temperatures are higher, and growth stress remains nearly constant across a range of continuous bias variations, with the increase in residual stress primarily due to thermal stress.