Nanoscale characterization of CH3-terminated Self-Assembled Monolayer on copper by advanced scanning probe microscopy techniques

Abstract

In this study, we used Self-Assembled Monolayer (SAM) with CH3 end-group molecules to protect copper surfaces from oxidation and investigated at nanometer scale the integrity and temperature stability of the protective film. The films were characterized by dynamic Chemical Force Microscopy (dCFM), Torsional Resonance Tunneling Atomic Force Microscopy (TR-TUNA) and Attenuated Total Reflection Fourier Transform Infrared Spectroscopy (ATR-FTIR).We observed that temperature stress degraded local properties of our SAM films significantly, when compared to unstressed films. After temperature stress at 100°C, tunneling current increased and hydrophobicity decreased substantially. In combination with the ATR-FTIR results we assigned local high current spots and local hydrophobic variations to cuprous oxide (Cu2O). After temperature stress at 150°C, the measurements indicate a decomposition of the SAM film and a further oxidation of the copper surface. In addition, the results show that dynamic dCFM and TR-TUNA are appropriate tools to characterize SAM films structurally, chemically and electrically. Most important, in contrast to conventional contact mode Atomic Force Microscopy techniques, we did not observe any damage to the SAM film by dCFM and TR-TUNA measurements.