Vacuum-Deposited Gold Films

The influence of the orientation of oxide-covered Si substrates on the morphology, overall surface roughness, and crystallographic texture of 35 nm thick evaporated gold films was investigated using scanning tunneling microscopy (STM), transmission electron microscopy (TEM), and cyclic voltammetry (CV). It is shown that gold films on Si (100) are substantially different from gold films on Si (111). The films deposited on Si (111) contain larger grains than those on Si (100). Annealed Au on Si (111) contains large atomically flat terraces which enable STM imaging at atomic resolution. The overall surface roughness measured by CV is smaller for annealed gold on Si (111), whereas for nonannealed samples, the gold on Si (100) is smoother. While very strong {111} texture is obtained for gold on Si (111), the Au on Si (100) is nontextured. Annealing of the gold films deposited on Si promotes grain enlargement, surface smoothness, and (for Si (111)) strong enhancement of the gold {111} texture. The different gold morphologies obtained on oxide-covered Si (111) and Si (100) are discussed in terms of the structural properties of the Si/Si oxide interface.