Abstract
The aim of this paper is to provide criteria for optical artifacts recognition in reflection-mode apertureless scanning near-field optical microscopy, implementing demodulation techniques at higher harmonics. We show that optical images acquired at different harmonics, although totally uncorrelated from the topography, can be entirely due to far-field artifacts. Such observations are interpreted by developing the dipole-dipole model for the detection scheme at higher harmonics. The model, confirmed by the experiment, predicts a lack of correlation between the topography and optical images even for structures a few tens of nanometers high, due to the rectification effect introduced by the lock-in amplifier used for signal demodulation. Analytical formulas deduced for the far-field background permit to simulate and identify all the different fictitious patterns to be expected from metallic nanowires or nanoparticles of a given shape. In particular, the background dependence on the tip-oscillation amplitude is put forward as the cause of the error-signal artifacts, suggesting, at the same time, specific fine-tuning configurations for background-free imaging. Finally a careful analysis of the phase signal is carried out. In particular, our model correctly interprets the steplike dependence observed experimentally of the background phase signal versus the tip-sample distance, and suggests to look for smooth variations of the phase signal for unambiguous near-field imaging assessment.
| Original language | English |
|---|---|
| Article number | 064303 |
| Journal | Journal of Applied Physics |
| Volume | 101 |
| Issue number | 6 |
| DOIs | |
| Publication status | Published - 2007 Apr 8 |
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ASJC Scopus subject areas
- Physics and Astronomy (miscellaneous)
- Physics and Astronomy(all)
Cite this
Artifacts identification in apertureless near-field optical microscopy. / Gucciardi, P. G.; Bachelier, G.; Allegrini, M.; Ahn, J.; Hong, M.; Chang, S.; Jhe, W.; Hong, Seok Cheol; Baek, S. H.
In: Journal of Applied Physics, Vol. 101, No. 6, 064303, 08.04.2007.Research output: Contribution to journal › Article
}
TY - JOUR
T1 - Artifacts identification in apertureless near-field optical microscopy
AU - Gucciardi, P. G.
AU - Bachelier, G.
AU - Allegrini, M.
AU - Ahn, J.
AU - Hong, M.
AU - Chang, S.
AU - Jhe, W.
AU - Hong, Seok Cheol
AU - Baek, S. H.
PY - 2007/4/8
Y1 - 2007/4/8
N2 - The aim of this paper is to provide criteria for optical artifacts recognition in reflection-mode apertureless scanning near-field optical microscopy, implementing demodulation techniques at higher harmonics. We show that optical images acquired at different harmonics, although totally uncorrelated from the topography, can be entirely due to far-field artifacts. Such observations are interpreted by developing the dipole-dipole model for the detection scheme at higher harmonics. The model, confirmed by the experiment, predicts a lack of correlation between the topography and optical images even for structures a few tens of nanometers high, due to the rectification effect introduced by the lock-in amplifier used for signal demodulation. Analytical formulas deduced for the far-field background permit to simulate and identify all the different fictitious patterns to be expected from metallic nanowires or nanoparticles of a given shape. In particular, the background dependence on the tip-oscillation amplitude is put forward as the cause of the error-signal artifacts, suggesting, at the same time, specific fine-tuning configurations for background-free imaging. Finally a careful analysis of the phase signal is carried out. In particular, our model correctly interprets the steplike dependence observed experimentally of the background phase signal versus the tip-sample distance, and suggests to look for smooth variations of the phase signal for unambiguous near-field imaging assessment.
AB - The aim of this paper is to provide criteria for optical artifacts recognition in reflection-mode apertureless scanning near-field optical microscopy, implementing demodulation techniques at higher harmonics. We show that optical images acquired at different harmonics, although totally uncorrelated from the topography, can be entirely due to far-field artifacts. Such observations are interpreted by developing the dipole-dipole model for the detection scheme at higher harmonics. The model, confirmed by the experiment, predicts a lack of correlation between the topography and optical images even for structures a few tens of nanometers high, due to the rectification effect introduced by the lock-in amplifier used for signal demodulation. Analytical formulas deduced for the far-field background permit to simulate and identify all the different fictitious patterns to be expected from metallic nanowires or nanoparticles of a given shape. In particular, the background dependence on the tip-oscillation amplitude is put forward as the cause of the error-signal artifacts, suggesting, at the same time, specific fine-tuning configurations for background-free imaging. Finally a careful analysis of the phase signal is carried out. In particular, our model correctly interprets the steplike dependence observed experimentally of the background phase signal versus the tip-sample distance, and suggests to look for smooth variations of the phase signal for unambiguous near-field imaging assessment.
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UR - http://www.scopus.com/inward/citedby.url?scp=34047096826&partnerID=8YFLogxK
U2 - 10.1063/1.2696066
DO - 10.1063/1.2696066
M3 - Article
AN - SCOPUS:34047096826
VL - 101
JO - Journal of Applied Physics
JF - Journal of Applied Physics
SN - 0021-8979
IS - 6
M1 - 064303
ER -