What is the direction of charge transfer between Aluminum and aliphatic amines physisorbed on top?
Amines could bond to the aluminum surface via a Lewis acid-base reaction between the electron rich amine nitrogen and the electron poor Al atom on the surface (perhaps formed by loss of a surface hydroxyl group as hydroxide ion). The direction of charge transfer would be from the amine nitrogen to an aluminum atom. The resulting "Lewis salt" would have a partial positive charge on nitrogen and a partial negative charge on aluminum (like an aluminate ion or an amine-aluminum chloride adduct).