Field enhancement of optical radiation in the nearfield of scanning probe microscope tips

Jersch, J.; Demming, F.; Hildenhagen, L.J.; Dickmann, K.

doi:10.1007/s003390050633

Cited by 81 publications

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“…This seems to be a promising method since a high degree of reproducibility has been reported [3][4][5]. Furthermore this method is applicable to different materials (for example Au, Au/Pd, Ti, PMMA, polycarbonate, organic media) as well as with different kinds of microscopes (AFM and STM) [3][4][5]. However, the responsible mechanism is controversial.…”

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confidence: 99%

“…Finally it is shown that even a huge increase of the involved electromagnetic field, reached by the reduction of the pulse length from 10 ns to 100 fs, does not change this scenario. Recent experiments have shown the possibility of surface nanostructuring by illumination of a scanning microscope tip with ns laser pulses [1][2][3][4][5]. This seems to be a promising method since a high degree of reproducibility has been reported [3][4][5].…”

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confidence: 99%

“…However, the responsible mechanism is controversial. On one hand field enhancement in the vicinity of the tip and subsequent field evaporation is proposed, while thermal effects are ruled out [1][2][3][4][5]. On the other hand mechanical contact as a result of thermal expansion is discussed as well [6][7][8].…”

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confidence: 99%

“…61.16.Ch; 65.70.+y Recent experiments have shown the possibility of surface nanostructuring by illumination of a scanning microscope tip with ns laser pulses [1][2][3][4][5]. This seems to be a promising method since a high degree of reproducibility has been reported [3][4][5]. Furthermore this method is applicable to different materials (for example Au, Au/Pd, Ti, PMMA, polycarbonate, organic media) as well as with different kinds of microscopes (AFM and STM) [3][4][5].…”

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The mechanism of nanostructuring upon nanosecond laser irradiation of a STM tip

Boneberg

Münzer

Tresp

et al. 1998

Applied Physics A: Materials Science & Processing

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Abstract. The mechanism of nanostructuring by illumination of scanning probe tips is examined. For that purpose the tip of a scanning tunneling microscope is illuminated with nanosecond and femtosecond laser pulses. The observation of a transient increase of the tunneling current on the timescale of µs is indicative of thermal expansion, which amounts to several nm for the energy density necessary for the purpose of nanostructuring. Furthermore, quantized electrical resistance can be observed upon illumination, which shows the formation of mechanical contact between tip and surface. Thus it is concluded that the appearance of nanostructures (craters or mounds) is dominated by the cohesion properties of the tip/sample combination. Finally it is shown that even a huge increase of the involved electromagnetic field, reached by the reduction of the pulse length from 10 ns to 100 fs, does not change this scenario. 61.16.Ch; 65.70.+y Recent experiments have shown the possibility of surface nanostructuring by illumination of a scanning microscope tip with ns laser pulses [1][2][3][4][5]. This seems to be a promising method since a high degree of reproducibility has been reported [3][4][5]. Furthermore this method is applicable to different materials (for example Au, Au/Pd, Ti, PMMA, polycarbonate, organic media) as well as with different kinds of microscopes (AFM and STM) [3][4][5]. However, the responsible mechanism is controversial. On one hand field enhancement in the vicinity of the tip and subsequent field evaporation is proposed, while thermal effects are ruled out [1][2][3][4][5]. On the other hand mechanical contact as a result of thermal expansion is discussed as well [6][7][8]. Such thermal effects have also been observed in other combinations of pulsed laser light with scanning microscope tips [9][10][11]. PACS:We performed transient measurements of the tunneling current during such experiments, which should enable us to distinguish between these two models due to the different time scales involved. Whereas a field evaporation mechanism should take place on the time scale of the laser pulse (ns), a thermal effect occurs with a typical cooling time in the order of µs (from τ = d 2 /2D one can estimate a relaxation time of 73 µs for a tungsten tip with a thermal diffusivity D of 0.68 cm 2 /s and a focus diameter d = 100 µm). Following the thermal model it might also be possible to observe indications of the mechanical contact, for example quantized conductance of the junction formed upon illumination. Therefore we present measurements of the gap resistance of a STM upon illumination with a ns laser pulse. Finally a comparison of current transients after illumination with ns and fs laser pulses, respectively, is shown.

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The mechanism of nanostructuring upon nanosecond laser irradiation of a STM tip

Boneberg

Münzer

Tresp

et al. 1998

Applied Physics A: Materials Science & Processing

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“…The tip shape may be approximated as an ellipsoid with a very high aspect ratio. For P-polarized excitation light and y-component (the component perpendicular to the sample surface) of the optical field the exact analytic solution of the Laplace equation (Jersch et al, 1998) gives E tip (v) 1E y0 (v) where 1 is the dielectric constant of the tip, E y0 is the incoming field and E tip is the y-component of the field just below the tip apex. As a result, for the incidence angles a around p/2 the local SHG under the tip is enhanced by a factor of n 8 (as…”

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Near‐field second harmonic imaging of the c/a/c/a polydomain structure of epitaxial PbZr_xTi_1–xO₃ thin films

Smolyaninov¹,

Liang²,

Lee³

et al. 2001

Journal of Microscopy

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SummaryNear-field optical second harmonic microscopy has been applied to imaging of the c/a/c/a polydomain structure of epitaxial PbZr x Ti 1±x O 3 thin films in the 0 , x , 0.4 range.Comparison of the near-field optical images and the results of atomic force microscopy and X-ray diffraction studies show that an optical resolution of the order of 100 nm is achieved. Symmetry properties of the near-field second harmonic signal allow us to obtain good optical contrast between the local second harmonic generation in c-and a-domains. Experimentally measured near-field second harmonic images have been compared with the results of theoretical calculations. Good agreement between theory and experiment is demonstrated. Experimental resultsOptical second harmonic generation (SHG) is a sensitive technique for characterization and investigation of the symmetry properties of different samples (Shen, 1984). It is known to be affected by crystal structure, magnetic and ferroelectric order, mechanical strain, etc. Very recently we have introduced an apertureless near-field optical technique for second harmonic imaging using a bare tapered optical fibre tip externally illuminated with femtosecond laser pulses (Smolyaninov et al., 2000). We have presented initial evidence of high spatial resolution of this technique (of the order of 80 nm), and indicated its sensitivity to local crystal symmetry. In this paper, we apply our technique to the imaging of polydomain c/a/c/a structures (consisting of alternating c-domains with the tetragonal axis perpendicular to the film±substrate interface, and a-domains with the c axis of the tetragonal film along either [100] or [010] directions of the substrate) that are commonly observed in thin epitaxial PbZr x Ti 1±x O 3 films in the 0 , x , 0.4 range, and in many other ferroelectric films such as BaTiO 3 , PbTiO 3 , KNbO 3 , etc. (Alpay et al., 1999). We also perform theoretical analysis of our images based on the symmetry properties of the near-field SH signal for different orientations of the poling direction of a poled single crystal of BaTiO 3 . Although simple and qualitative, such an analysis allows us to obtain impressive agreement with the data of experimental measurements. Using this theory, we also analyse the transition from the near-field to the far-field mode of operation of our microscope. This study provides necessary justification for the developed procedure of local poling direction recovery of individual ferroelectric domains in polycrystalline thin ferroelectric films.Our experimental set-up is shown in Fig. 1. Weakly focused light (illuminated spot diameter on the order of 50 mm) from a Ti: sapphire laser system consisting of an oscillator and a regenerative amplifier operating at 810 nm (repetition rate up to 250 kHz, 100 fs pulse duration, and up to 10 mJ pulse energy) was directed at an angle of incidence around 508 onto the sample surface. Excitation power at the sample surface was kept well below the ablation threshold. The local SHG was collected using an uncoate...

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Raman and Fluorescence Spectroscopy Coupled with Scanning Tunneling Microscopy

Horimoto

Fukumura

2009

Molecular Nano Dynamics

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Field enhancement of optical radiation in the nearfield of scanning probe microscope tips

Cited by 81 publications

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The mechanism of nanostructuring upon nanosecond laser irradiation of a STM tip

The mechanism of nanostructuring upon nanosecond laser irradiation of a STM tip

Near‐field second harmonic imaging of the c/a/c/a polydomain structure of epitaxial PbZr_xTi_1–xO₃ thin films

Raman and Fluorescence Spectroscopy Coupled with Scanning Tunneling Microscopy

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Field enhancement of optical radiation in the nearfield of scanning probe microscope tips

Cited by 81 publications

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The mechanism of nanostructuring upon nanosecond laser irradiation of a STM tip

The mechanism of nanostructuring upon nanosecond laser irradiation of a STM tip

Near‐field second harmonic imaging of the c/a/c/a polydomain structure of epitaxial PbZrxTi1–xO3 thin films

Raman and Fluorescence Spectroscopy Coupled with Scanning Tunneling Microscopy

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Near‐field second harmonic imaging of the c/a/c/a polydomain structure of epitaxial PbZr_xTi_1–xO₃ thin films