Stability of Silver Nanoparticles Fabricated by Nanosphere Lithography and Atomic Layer Deposition to Femtosecond Laser Excitation

In this paper, we compare the stability of silver nanoparticles fabricated by nanosphere lithography (NSL) and those coated with atomic layers of Al2O3 to femtosecond laser pulses. Structural changes in the nanoparticles caused by the laser pulses were monitored by UV−vis extinction spectroscopy. It is demonstrated that 1.0 nm thick Al2O3 layers fabricated by atomic layer deposition (ALD) provide a factor of 10 improvement in the stability of the silver nanoparticles against femtosecond laser exposure compared to that for bare nanoparticles. The enhanced stability caused by the Al2O3 layers is explained by the increased surface melting temperature resulting from the decreased mean square displacement of silver atoms located on the nanoparticle surface. This study demonstrates that Al2O3-coated nanoparticles can serve as a stable platform for both linear and nonlinear ultrafast surface-enhanced laser spectroscopy.