AVS 52nd International Symposium
    Thin Films Tuesday Sessions
       Session TF-TuM

Paper TF-TuM9
Atomic Layer Deposition for the Modification and Stabilization of Localized Surface Plasmon Resonance Nanosensors

Tuesday, November 1, 2005, 11:00 am, Room 306

Session: Atomic Layer Deposition - Oxides
Presenter: J.W. Elam, Argonne National Laboratory
Authors: J.W. Elam, Argonne National Laboratory
M.J. Pellin, Argonne National Laboratory
A.V. Whitney, Northwestern University
R.P. Van Duyne, Northwestern University
P.C. Stair, Northwestern University
G.C. Schatz, Northwestern University
S. Zou, Northwestern University
Correspondent: Click to Email
Noble metal nanoparticles serve as optical biosensors and chemosensors because of the localized surface plasmon resonance (LSPR) effect. The optical properties of LSPR sensors are strongly influenced by the size, shape and dielectric environment of the nanoparticles. Atomic layer deposition (ALD) can deposit dielectric films with atomic layer precision onto a variety of substrates including noble metals. Consequently, the optical properties of LSPR sensors can be tailored using ALD coatings. In this study, ordered arrays of Ag nanoparticles were coated with ALD Al@sub2@O@sub3@ and the resulting changes in the physical properties of the nanoparticles were explored. Initial experiments examined the nucleation and growth of ALD Al@sub2@O@sub3@ on flat Ag surfaces using quartz crystal microbalance and ellipsometry measurements. Surprisingly, these measurements demonstrated that the Al@sub2@O@sub3@ ALD proceeds on Ag without any nucleation delay. Next, ordered arrays of Ag nanotriangles fabricated using nanosphere lithography were coated using ALD Al@sub2@O@sub3@ at 50 °C. Optical absorption measurements revealed a 6 nm red shift in the LSPR peak for an Al@sub2@O@sub3@ thickness of only 1.6 Å. The LSPR peak continues to red shift with increasing Al@sub2@O@sub3@ thickness up to ~600 Å. These changes are explained well by theoretical analysis using finite element electrodynamics. The Ag nanotriangles were also examined using atomic force microscopy and scanning electron microscopy and these measurements demonstrated that the ALD Al@sub2@O@sub3@ conformally coats the nanotriangles while preserving their initial shape. Preliminary experiments reveal that thin ALD Al@sub2@O@sub3@ layers significantly improve the thermal stability of Ag nanoparticles while retaining strong Raman enhancement, suggesting that ALD coatings will broaden the range of applications for LSPR nanosensors.