Setup Results and Discussion Conclusion Acknowledgement 2
SURFACE PLASMON RESONANCE(SPR) Collective
oscillation of conduction electrons on the surface of metallic nanostructures. Resonance occurs when incident light = natural of oscillation Quantized plasma wave: plasmons Coupled plasmon oscillations →evanescent waves
3 gregemmerich.wordpress.com
EVANESCENT WAVES Confined
to surface Exponentially decaying Resolution better than λ explained by position - momentum uncertainty
Dielectric
Metal
a) Plasmonics b) Introducing an aperture (below the diffraction limit) 4 Fig:Kawata, S.; Inouye, Y.; Verma, P., Plasmonics for near-field nano-imaging and super-lensing. Nature Photonics 2009, 3 (7), 388-394.
IEEE Sensors Journal, Vol. 14, No. 9, September 2014
DISPERSION RELATION (i) Light (ii) Evanescent waves (iii) Surface plasmon
k
vg
k sp
c/n
c
d . m c d m
(i)
(ii)
(iii)
Kawata, S.; Inouye, Y.; Verma, P., Plasmonics for near-field nano-imaging and super-lensing. Nature Photonics 2009, 3 (7), 388-394.
6
KEY ADVANTAGES 1. The Resolution of NSOM imaging is mainly dependent on the Wavelength of the evanescent wave. “ There is NO relation between Resolution and Excitation Frequency.” 2. At the Plasmon Resonance, the frequency of an excitation wave is a conserved quantity “Only the components of Excitation wave vector changes.”
7
EXPERIMENTAL SETUP Resonace freq of cantilever ~ 37.5 MHz
Quality factor Q ~ 2000
8
OPTICALLY COUPLED SCANNING PROBE MICROSCOPY
9
RESULTS AND DISCUSSION 10
AFM and NSOM image for Au NPs 20.57 nm
0.8
0.7
0.6
0.6
0.5
0.5
0.4
0.4
Y[µm]
0.7
0.3 0.2
0.3 0.2
0.1
0.1
0
0
0
0.2
0.4
0.6
0.8
299.92 KHz
0.8
0
1
0.2
0.4
0.6
0.8
-20.57 nm
Topography Map X[µm]
1 -303.16 KHz
Optical Map X[µm]
11
Absorbance plot of Au NPs
12
Inset: FESEM image of Au nanoparticles
NSOM 3D
NSOM 2D Line Profile Topo 2D
Topo 3D 13
14
CONCLUSION
Simultaneous AFM and NSOM image of Au NPs obtained.
Strong absorption of incident radiation observed in SPR active (Au NPs) materials.
