| AVS 57th International Symposium & Exhibition | |
| Electronic Materials and Processing | Tuesday Sessions |
| Session EM-TuM |
| Session: | Contacts and Transport |
| Presenter: | A.V. Walker, University of Texas at Dallas |
| Authors: | Z. Shi, University of Texas at Dallas A.V. Walker, University of Texas at Dallas |
| Correspondent: | Click to Email |
We have investigated the reaction pathways involved in the electroless deposition of nickel on -COOH, -OH, and -CH3 terminated functionalized alkanethiolate self-assembled monolayers (SAMs) adsorbed on gold, using time-of-flight secondary ion mass spectrometry (TOF SIMS), scanning electron microscopy (SEM) and x-ray photoelectron spectroscopy (XPS) . This work has important applications in molecular/organic electronics as well as other technologies.
We observe that the nickel electroless deposition rate increases as the plating bath pH increases. For -COOH, terminated SAMs, this is effect is very pronounced, with the largest deposition rates observed at above pH = 9. This is most likely due to the –COOH terminated groups deprotonating to form forming carboxylate ions, COO-. These carboxylate ions can easily complex with Ni2+ ions in solution, forming Ni-carboxylate complexes which serve as the nucleation sites for Ni deposition. Furthermore on -COOH terminated SAMs the nickel overlayer forms almost immediately, while on -CH3 and -OH terminated SAMs the nickel overlayer forms after 15-20 minutes deposition. The nucleation of the Ni overlayer is slightly faster on the hydrophobic -CH3 terminated SAM than on the hydrophilic -OH terminated SAM.
By exploiting the different nickel deposition rates on -COOH, -OH, and -CH3 terminated SAMs we demonstrate that a variety of nanostructures can be produced, including nanowires and rings, using micron-scale patterned SAM surfaces.