We present the results of an IR study of the effect of temperature on the formation of Au-monolayer-Si molecular junctions by using a flip-chip lamination approach. Carboxylic acid-terminated alkanethiols self-assembled on ultrasmooth gold substrate have been laminated to H-Si(111) at 0.8 MPa as a function of temperature. p-Polarized-backside reflection absorption infrared spectroscopy of the alkanoic acids within the molecular junction indicate increasing disorder, likely near the COOH terminus, of the all-trans chain up to 60oC, followed by a propagation of these defects down the molecular length. The IR spectra of the Si-O and C-O regions as a function of temperature indicate the -COOH group is interacting with the H-Si(111) surface through a bidentate coordination mode. The IR spectra indicate the reaction is largely due to the availability of the COOH groups to react. Flip-chip lamination is an effective approach to form molecular junctions. Unlike direct metal evaporation, it ensures the formation of robust structures where the organic monolayer is chemically bonded to both surfaces with no signs of metal penetration.
Citation: Journal of Vacuum Science and Technology
Pub Type: Journals