Influence of interfacial chemistry and molecular length on the electronic properties of metal-molecule-silicon junctions produced by flip chip lamination

The integration of organic molecules with silicon is increasingly being studied for potential uses in hybrid electronic devices. However, creating a dense and highly ordered organic monolayer on silicon with reliable metal-molecule contacts still remains a challenge. A novel technique, flip chip lamination (FCL), has been developed to create uniform, covalently bound metal-molecule-semiconductor junctions using nanotransfer printing.[1, 2] FCL is advantageous because it is a versatile technique that can be used for a variety of molecules, the molecular structure can be interrogated while in the device architecture, and it is a low cost scheme that preserves the integrity of the molecular self-assembled monolayers (SAMs) within the junction. This work reports on studies of several molecular SAMs to investigate the role of length dependence and molecular structure for metal-molecule-silicon junctions. The effects of the FCL process on the chemical and physical properties of the embedded molecular layer were examined with p-polarized backside reflectance absorption infrared spectroscopy (pb-RAIRS), spectroscopic ellipsometry, and water contact angle measurements. Electrical measurements were performed to characterize the electronic properties of the organic SAMs and to offer better insight into the mechanisms at play in the electronic transport through the metal-molecule-silicon junction.