Optically induced forces in scanning probe microscopy

Kohlgraf-Owens, Dana C.; Sukhov, Sergey; Greusard, L.; Wilde, Yannick De; Dogariu, Aristide

doi:10.1515/nanoph-2013-0056

Cited by 7 publications

(3 citation statements)

References 91 publications

(119 reference statements)

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“…This effect has been previously noted in tipilluminated AFM studies, and is known as the "optical force artifact". 32, 33 It results from the effective dc change in average tip−sample distance as a consequence of the sinusoidal modulation of the photoinduced force, which can be modeled as F PiF (1+cos(ω 2 t)). At low average illumination powers of 100 μW or less, this distance-dependent effect is usually sufficiently small as not to affect the topography image.…”

Section: ■ Imaging Properties Of Pifm Photoinduced Forces In the Focamentioning

confidence: 99%

Linear and Nonlinear Optical Spectroscopy at the Nanoscale with Photoinduced Force Microscopy

Jahng¹,

Fishman²,

et al. 2015

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The enormous advances made in nanotechnology have also intensified the need for tools that can characterize newly synthesized nanoaterials with high sensitivity and with high spatial resolution. Many existing tools with nanoscopic resolution or better, including scanning electron microscopy (SEM), atomic force microscopy (AFM), and scanning tunneling microscopy (STM) methods, can generate highly detailed maps of nanoscopic structures. However, while these approaches provide great views of the morphological properties of nanomaterials, it has proven more challenging to derive chemical information from the corresponding images. To address this issue, attempts have been made to dress existing nanoscopy methods with spectroscopic sensitivity. A powerful approach in this direction is the combination of scan probe techniques with optical illumination, which aims to marry the nanoscopic resolution provided by a sharp tip with the chemical selectivity provided by optical spectroscopy. Examples of this approach include existing techniques such as scattering-type scanning near-field optical microscopy and tip-enhanced Raman spectroscopy. A new and emerging technique in this direction is photoinduced force microscopy (PiFM), which enables spectroscopic probing of materials with a spatial resolution well under 10 nm. In PiFM, the sample is optically excited and the response of the material is probed directly in the near-field by reading out the time-integrated force between the tip and the sample. Because the magnitude of the force is dependent on the photoinduced polarization in the sample, PiFM exhibits spectroscopic sensitivity. The photoinduced forces measured in PiFM are spatially confined on the nanometer scale, which translates into a very high spatial resolution even under ambient conditions. The PiFM approach is compatible with a wide range optical excitation frequencies, from the visible to the mid-infrared, enabling nanoscale imaging contrast based on either electronic or vibrational transitions in the sample. These properties make PiFM an attractive method for the visualization and spectroscopic characterization of a vast variety of nano materials, from semiconducting nanoparticles to polymer thin films to sensitive measurements of single molecules. In this Account, we review the principles of the PiFM technique and discuss the basic components of the photoinduced force microscope. We highlight the imaging properties of the PiFM instrument and demonstrate the inherent spectroscopic sensitivity of the technique. Furthermore, we show that the PiFM approach can be used to probe both the linear and nonlinear optical properties of nano materials. In addition, we provide several examples of PiFM imaging applications.

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Section: ■ Imaging Properties Of Pifm Photoinduced Forces In the Focamentioning

confidence: 99%

Linear and Nonlinear Optical Spectroscopy at the Nanoscale with Photoinduced Force Microscopy

Jahng¹,

Fishman²,

et al. 2015

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“…3 (a, b)). This effect is related to the optical force artifact known in scattering near-field optical microscopy 32,33 .…”

Section: Amplitude-distance Simulationsmentioning

confidence: 99%

Quantitative analysis of sideband coupling in photoinduced force microscopy

et al. 2016

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We present a theoretical and experimental analysis of the cantilever motions detected in photoinduced force microscopy (PiFM) using the sideband coupling detection scheme. In sideband coupling, the cantilever dynamics are probed at a combination frequency of a fundamental mechanical eigenmode and the modulation frequency of the laser beam. Using this detection mode, we develop a method for reconstructing the modulated photo-induced force gradient from experimental parameters in a quantitative manner. We show evidence, both theoretically and experimentally, that the sideband coupling detection mode provides PiFM images with superior contrast compared to images obtained when detecting the cantilever motions directly at the laser modulation frequency.

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“…Alternatively, spectroscopic imaging through mechanical cantilever sensing of the weak optical force gradient arising from the interaction of the resonantly driven molecular dipole with the tip has been proposed. , However, questions remain about assignment of the observed experimental contrast, with thermal expansion and optical force difficult to distinguish a priori.…”

mentioning

confidence: 99%

Infrared Chemical Nano-Imaging: Accessing Structure, Coupling, and Dynamics on Molecular Length Scales

Muller

Pollard

Raschke

2015

J. Phys. Chem. Lett.

125

117

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This Perspective highlights recent advances in infrared vibrational chemical nano-imaging. In its implementations of scattering scanning near-field optical microscopy (s-SNOM) and photothermal-induced resonance (PTIR), IR nanospectroscopy provides few-nanometer spatial resolution for the investigation of polymer, biomaterial, and related soft-matter surfaces and nanostructures. Broad-band IR s-SNOM with coherent laser and synchrotron sources allows for chemical recognition with small-ensemble sensitivity and the potential for sensitivity reaching the single-molecule limit. Probing selected vibrational marker resonances, it gives access to nanoscale chemical imaging of composition, domain morphologies, order/disorder, molecular orientation, or crystallographic phases. Local intra- and intermolecular coupling can be measured through frequency shifts of a vibrational marker in heterogeneous environments and associated inhomogeneities in vibrational dephasing. In combination with ultrafast spectroscopy, the vibrational coherent evolution of homogeneous sub-ensembles coupled to their environment can be observed. Outstanding challenges are discussed in terms of extensions to coherent and multidimensional spectroscopies, implementation in liquid and in situ environments, general sample limitations, and engineering s-SNOM scanning probes to better control the nano-localized optical excitation and to increase sensitivity.

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Optically induced forces in scanning probe microscopy

Cited by 7 publications

References 91 publications

Linear and Nonlinear Optical Spectroscopy at the Nanoscale with Photoinduced Force Microscopy

Linear and Nonlinear Optical Spectroscopy at the Nanoscale with Photoinduced Force Microscopy

Quantitative analysis of sideband coupling in photoinduced force microscopy

Infrared Chemical Nano-Imaging: Accessing Structure, Coupling, and Dynamics on Molecular Length Scales

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