Pattern formation via the oriented growth of Au-Si thin films on Si (001) substrate

The fabrication of patterned surfaces is integral to various device manufacturing processes. These techniques, developed over time, enable the precise manipulation of surface properties at the nanoscale. In this study, we introduce a self-driven approach for patterning metal and semiconductor surfaces by solidifying eutectic Au-Si thin films on Si(001) substrates. The resulting pattern encompasses meticulously aligned rectangular Au-Si eutectic structures and Si islands, the orientations of which are determined by the substrate. This exceptional alignment is attributed to the epitaxial growth of Si(001) and the heteroepitaxial growth of Au(001) and Au(011) within the films. This conclusion was corroborated through selected area electron diffraction and synchrotron radiation grazing-incidence wide-angle X-ray scattering (GIWAXS). We propose a 4:3 coincident site lattice (CSL) model to elucidate the Au-Si interface, explaining the dominant (001)[110]Au||(001)[110]Si orientation rela- tionship that minimizes the Au/Si lattice mismatch to 0.2%. The other observed orientation relationships, (110) [001]Au||(001)[110]Si and (001)[010]Au||(001)[110]Si, entail a 6.3% mismatch in one or two directions, leading to contrasting elastic strains in the Au and Si lattices, accompanied by the accrual of elastic strain energy. This study underscores the practicality of substrate-oriented pattern formation, with potential applications in other phase-separated systems.