Nanoscale Roughness on Metal Surfaces Can Increase Tip-Enhanced Raman Scattering by an Order of Magnitude

Zhang, Weihua; Cui, Xudong; Yeo, Boon Siang; Schmid, Thomas; Hafner, Christian; Zenobi, Renato

doi:10.1021/nl070616n

Cited by 161 publications

(158 citation statements)

References 29 publications

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“…Recently, this effect has indeed been reported in both tip-enhanced fluorescence spectroscopy and TERS studies. [13,37] Therefore, further work is still needed in order to fully understand these details.…”

Section: Substrate Effectmentioning

confidence: 99%

“…Thanks to these merits, TERS has provided a direct proof for single-molecule Raman detection, [2,10 -12] an issue debated for almost 10 years in the SERS community. Furthermore, TERS also allows us to investigate the detailed physical properties of the 'hot' spots, such as the influence of nanometer-scale corrugation on the field enhancement [13] and thermal effects at the 'hot' spot. [14] Despite these achievements, our understanding of the enhancement mechanisms of TERS is still superficial.…”

Section: Introductionmentioning

confidence: 99%

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Local field enhancement of an infinite conical metal tip illuminated by a focused beam

Zhang

Cui

Martin

2009

J Raman Spectroscopy

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We present a systematic numerical investigation of conical metal tips which are commonly used in tip-enhanced Raman spectroscopy (TERS). Different from previous studies, we focus on how the tip length and the illumination condition influence the local field enhancement at the tip apex, and provide a useful reference for real experiments. In particular, we show that the type of illumination has a dramatic influence on the field enhancement: a localized illumination spot -as used in experiments -producing a very different response than a plane wave illumination -as usually used in previous models. Also, the effect of the different geometrical parameters, such as the sharpness of the tip apex and the cone angle, provides guidance to optimize the tip design. Finally, we investigate the influence of the substrate and compare numerical data with results deduced from a simplified model, finding good agreement. This brings new insights into the enhancement mechanism of TERS.

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Section: Substrate Effectmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Local field enhancement of an infinite conical metal tip illuminated by a focused beam

Zhang

Cui

Martin

2009

J Raman Spectroscopy

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“…Their hot spots can be used to trigger nonlinear effects and to couple electromagnetic radiation efficiently between the antennas and dipole emitters. Experimental techniques such as tip enhanced Raman spectroscopy or surface enhanced Raman spectroscopy demonstrate the potential of such hot spots to detect radiative emitters with sensitivity down to a single molecule [13][14][15][16][17][18][19]. The enhancement of the fluorescence of molecules placed near a plasmonic nanostructure has been observed recently, tuning the plasmon resonance either to the excitation or the emission of the molecules [20][21][22][23].…”

Section: Introductionmentioning

confidence: 99%

Engineering the optical response of plasmonic nanoantennas

2008

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Abstract:The optical properties of plasmonic dipole and bowtie nanoantennas are investigated in detail using the Green's tensor technique. The influence of the geometrical parameters (antenna length, gap dimension and bow angle) on the antenna field enhancement and spectral response is discussed. Dipole and bowtie antennas confine the field in a volume well below the diffraction limit, defined by the gap dimensions. The dipole antenna produces a stronger field enhancement than the bowtie antenna for all investigated antenna geometries. This enhancement can reach three orders of magnitude for the smallest examined gap. Whereas the dipole antenna is monomode in the considered spectral range, the bowtie antenna exhibits multiple resonances. Furthermore, the sensitivity of the antennas to index changes of the environment and of the substrate is investigated in detail for biosensing applications; the bowtie antennas show slightly higher sensitivity than the dipole antenna.

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“…3 While it is based on the same phenomenon as SERS, tipenhanced Raman scattering (TERS) can circumvent these limitations and achieve complete substrate generality. [4][5][6][7][8] When a metallic probe outfitted with a nanometric tip is illuminated with an optical field, conductive free electrons collectively oscillate at the surface of the metal. The electrons (and the positive charge) are concentrated at the tip apex and generate a strong external electric field.…”

Section: Introductionmentioning

confidence: 99%

Chemical and electromagnetic mechanisms of tip-enhanced Raman scattering

Sun

Fang

Yang

et al. 2009

Phys. Chem. Chem. Phys.

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In this paper, we attempt to reveal the nature of the chemical and electromagnetic mechanisms of tip-enhanced Raman scattering (TERS). Direct visual evidence regarding the chemical mechanism via charge transfer was obtained with charge difference density. It is found that there are several kinds of charge transfer: (1) tip to molecule, (2) surface to molecule, (3) tip and surface to molecule simultaneously, and (4) tunneling charge transfer between the tip and the surface. Direct evidence regarding the electromagnetic mechanism via intracluster (tip or surface) charge redistribution was also revealed via charge difference density. The distance (between tip and surface) dependence of the near electric field distribution and the TERS enhancement at different incident lights is also discussed using the three-dimensional finite-difference time-domain (FDTD) method. The electromagnetic enhancement of double-tip TERS is approximately 10 times larger than that of conventional TERS. Theoretical results reveal that plasmon coupling effects between the metal tip and surface play an important role in TERS.

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Nanoscale Roughness on Metal Surfaces Can Increase Tip-Enhanced Raman Scattering by an Order of Magnitude

Cited by 161 publications

References 29 publications

Local field enhancement of an infinite conical metal tip illuminated by a focused beam

Local field enhancement of an infinite conical metal tip illuminated by a focused beam

Engineering the optical response of plasmonic nanoantennas

Chemical and electromagnetic mechanisms of tip-enhanced Raman scattering

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