Atomic layer deposition (ALD) is used to deposit 1-600 monolayers of Al 2O 3 on Ag nanotriangles fabricated by nanosphere lithography (NSL). Each monolayer of Al 2O 3 has a thickness of 1.1 Å. It is demonstrated that the localized surface plasmon resonance (LSPR) nanosensor can detect Al 2O 3 film growth with atomic spatial resolution normal to the nanoparticle surface. This is approximately 10 times greater spatial resolution than that in our previous long-range distance-dependence study using multilayer self-assembled monolayer shells. The use of ALD enables the study of both the long- and short-range distance dependence of the LSPR nanosensor in a single unified experiment. Ag nanoparticles with fixed in-plane widths and decreasing heights yield larger sensing distances. X-ray photoelectron spectroscopy, variable angle spectroscopic ellipsometry, and quartz crystal microbalance measurements are used to study the growth mechanism. It is proposed that the growth of Al 2O 3 is initiated by the decomposition of trimethylaluminum on Ag. Semiquantitative theoretical calculations were compared with the experimental results and yield excellent agreement.
ASJC Scopus subject areas
- Physical and Theoretical Chemistry