Adsorption of Al on Si(100) at high temperature

A scanning tunneling microscopy investigation on the adsorption structure of Al on Si(100) deposited at substrate temperature of $500°\mathrm{C}$ is presented. The adsorption at high substrate temperature leads to a strong interaction of Al adatoms with surface atoms of Si(100) to form Al-Si subunits on the Si(100) surface. A structural model is proposed to describe the registration and composition of Al-Si subunits in terms of the charge transfer and the spatial distribution of the surface states. It is considered that each Al-Si subunit is composed of four Al atoms and one Si atom.