AVS 45th International Symposium
    Biomaterial Interfaces Group Tuesday Sessions
       Session BI+AS+MM+NS+SS-TuA

Paper BI+AS+MM+NS+SS-TuA3
Nanofabricated Substrates for Probing Single Biomolecules by Surface Enhanced Raman Scattering

Tuesday, November 3, 1998, 2:40 pm, Room 326

Session: Nanoscale to Mesocale Biomaterial Structures
Presenter: S. Petronis, Chalmers Univ. of Technology and Univ. of Gothenborg, Sweden
Authors: S. Petronis, Chalmers Univ. of Technology and Univ. of Gothenborg, Sweden
L.K. Hedberg, Chalmers Univ. of Technology and Univ. of Gothenborg, Sweden
H. Xu, Chalmers Univ. of Technology and Univ. of Gothenborg, Sweden
M. Käll, Chalmers Univ. of Technology and Univ. of Gothenborg, Sweden
B. Kasemo, Chalmers Univ. of Technology and Univ. of Gothenborg, Sweden
Correspondent: Click to Email
The effect of Raman scattering enhancement when coherent laser light interacts with molecules attached to rough surfaces and microscopic metal domains has been known for more than two decades and is called Surface Enhanced Raman Scattering (SERS). The intensity of the Raman signals for such molecules is frequently enhanced by a factor 10@super 5@-10@super 6@ at best.@footnote 1,2@ However recently much larger enhancement factors, in the range 10@super 14@-10@super 15@, have been observed for molecules adsorbed on colloidal silver particles of specific dimensions.@footnote 3,4@ This giant enhancement allows the recording of vibrational spectra from a single molecule for the first time, instead of the ensemble averaged spectra from many molecules, which are normally obtained in optical spectroscopies. Here we report on an attempt to use nanolithography to fabricate structures of silver in the size range 100 - 200 nm and having different shapes in order to explore the size and geometry dependence of the SERS effect. Microfabricated structures which give the highest enhancement could be used for probing different biomolecules and perhaps designing a biosensor. SERS active substrates were prepared as arrays of silver particles on a Si wafer. Within each array the silver particles had a constant shape, size and separation. Three particle shapes (circular, triangular and square), two particle sizes (100 nm and 200 nm), and five different particle separations (10, 50, 100, 150 and 200 nm) were produced by electron beam lithography with a double-layer resist system and "lift-off" procedure. A reference area of uniformly deposited Ag film mimicked an infinite silver surface. The final structures and the chemical composition of the silver particles were characterized by Scanning Electron Microscopy (SEM) and Auger electron spectroscopy (AES), respectively. Preliminary Raman scattering experiments have been performed on the dye-molecule Rhodamin 6G adsorbed on the nanofabricated substrates. A giant enhancement of the Raman signal was observed on all patterns, but not on the Ag film or the Si surface. @FootnoteText@ @footnote 1@M.Moskovits, Rev. of Mod. Phys., vol. 57, No 3, 1985, pp 783-826 @footnote 2@A.G.Mal'shukov, Phys. Rep., vol 194, Nos 5&6, 1990, pp 343-349 @footnote 3@K.Kneip et al., Phys. Rev. Lett., vol. 78, No 9, 1997, pp1667-1670 @footnote 4@S.Nie, S.R. Emory, Science, vol. 275, No 21, 1997, pp 1102-1106