Nucleation and Growth of Vapor-Deposited Metal Films on Self-Assembled Monolayers Studied by Multiple Characterization Probes

Abstract

The vapor deposition of Al atoms on self-assembled monolayers was studied by IR spectroscopy, XPS, time-of-flight secondary ion mass spectrometry, and spectroscopic ellipsometry. The SAMs consisted of terminally substituted hexadecanethiolates [X(CH2)15S-] on Au{111} surfaces with X = -CH3, -CO2H, -CO2CH3, OH and OCH3. When a reactive group was present at the alkyl chain terminus, nucleation and growth of a metallic film occurred only at the vacuum/film interface and the first several layers of Al atoms appeared to form an organoaluminum dielec. layer prior to the growth of a metallic film. When the chain terminus contained an unreactive CH3 group, penetration through the SAM to the S/Au interface occurred. This penetration was suggested to occur via a thermally activated lateral hopping process of the SAM mols., leading to the creation of transient holes allowing transport of nearby Al atoms directly to the S/Au interface.