STM study of the initial stages of AlF3 on Cu(100)

In this study we present results concerning the early growth stages of an insulator-metal interface by means of scanning tunneling microscopy. We report the growth of aluminum fluoride (AlF3) films over a Cu(100) surface at room temperature, from submonolayer coverages up to 1.25 monolayers. Scanning tunneling microscopy (STM) measurements reveal that aluminum fluoride islands undergo a shape transition at very low coverages, from compact to fractal-like, as they grow in size. These fractal-like islands cover the substrate with a single monolayer film up to depositions of 0.80 monolayers, while for larger coverages the growth results in the formation of three dimension islands. Kinetic Monte Carlo simulations help us to understand some issues of the growth mechanism. High voltages (V >= 2.50 V) are needed to obtain STM images, showing the insulator character of the AlF3 islands.