Self-assembled nanocomposite structure of Si-Au system formed by liquid phase epitaxy

A composite structure of Si and Au was formed by a self-assembly process on a nanometer scale. Au fine particles generated by a gas-phase condensation method were deposited on a single-crystalline Si(1 1 1) substrate. Through a heat treatment and a cooling process, a nanocomposite structure of Si-Au was formed on the surface of the Si substrate. This structure was produced by three steps as follows. First, a Si-Au droplet was formed on the Si surface at an elevated temperature. Second, the Si atoms were precipitated from the Si-Au droplet during the cooling process. Finally, Si and Au completely separated, forming a nanocomposite structure of Si-Au below the eutectic temperature. As a result, Si/metal heterointerface could be fabricated on a nanometer scale. Additionally, observation of a high-resolution transmission electron microscopy (HRTEM) revealed that precipitated Si dots had an epitaxial relation with the Si substrate. Namely, the Au fine particles played the role of a transport medium in the process of liquid phase epitaxy (LPE).