Effect of the surface water layer on the optical signal in apertureless scanning near field optical microscopy

Huang, Fanglu; Culfaz, Ferhat; Festy, Frederic; Richards, David

doi:10.1088/0957-4484/18/1/015501

Cited by 11 publications

(9 citation statements)

References 20 publications

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“…Laboratory air also has a significant amount of water vapor, where the partial pressure of water depends on temperature and relative humidity (RH). If RH is greater than zero, all surfaces (hydrophobic or hydrophilic) exposed to air 39,40 adsorb a water-layer with a thickness dependent on the exposure time, temperature, RH and the sample's hydrophilic or hydrophobic character [41][42][43][44] .…”

Section: Ambient Conditions: the Hydration Layermentioning

confidence: 99%

Optimizing atomic resolution of force microscopy in ambient conditions

2013

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Ambient operation poses a challenge to atomic force microscopy because in contrast to operation in vacuum or liquid environments, the cantilever dynamics change dramatically from oscillating in air to oscillating in a hydration layer when probing the sample. We demonstrate atomic resolution by imaging of the KBr(001) surface in ambient conditions by frequency-modulation atomic force microscopy with a cantilever based on a quartz tuning fork (qPlus sensor) and analyze both long-and short-range contributions to the damping. The thickness of the hydration layer increases with relative humidity; thus varying humidity enables us to study the influence of the hydration layer thickness on cantilever damping. Starting with measurements of damping versus amplitude, we analyzed the signal and the noise characteristics at the atomic scale. We then determined the optimal amplitude which enabled us to acquire high-quality atomically resolved images.

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Section: Ambient Conditions: the Hydration Layermentioning

confidence: 99%

Optimizing atomic resolution of force microscopy in ambient conditions

2013

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“…This is a matter of both long-running [4] and topical interest [5,6] in the context of atomic force microscopy, especially in applications such as dip pen lithography [7]. A tip-sample water bridge also plays a critical role in instrument operation in configurations in which tip-sample distance regulation relies on the detection of a shear force between a laterally dithered tip and the sample a scheme that is widely adopted in scanning near-field optical microscopy [8,9]. The detailed mechanism of water bridge formation in SPM has also been addressed though molecular dynamics simulations [10].…”

Section: Introductionmentioning

confidence: 99%

The tip–sample water bridge and light emission from scanning tunnelling microscopy

Boyle¹,

Mitra²,

Dawson³

2009

Nanotechnology

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The light emission spectrum from a scanning tunnelling microscope (LESTM) is investigated as a function of relative humidity and shown to provide a novel and sensitive means for probing the growth and properties of a water meniscus on the nanometre scale. An empirical model of the light emission process is formulated and applied successfully to replicate the decay in light intensity and spectral changes observed with increasing relative humidity. The modelling indicates a progressive water filling of the tip-sample junction with increasing humidity or, more pertinently, of the volume of the localized surface plasmons responsible for light emission; it also accounts for the effect of asymmetry in structuring of the water molecules with respect to the polarity of the applied bias. This is juxtaposed with the case of a non-polar liquid in the tip-sample nanocavity where no polarity dependence of the light emission is observed. In contrast to the discrete detection of the presence/absence of a water bridge in other scanning probe experiments through measurement of the feedback parameter for instrument control, LESTM offers a means of continuously monitoring the development of the water bridge with sub-nanometre sensitivity. The results are relevant to applications such as dip-pen nanolithography and electrochemical scanning probe microscopy.

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“…Ambient air contains a significant amount of water vapor, where the partial pressure of water depends on temperature and relative humidity (RH). If humidity is present, all surfaces (hydrophobic or hydrophilic) exposed to air adsorb a water layer. − The water layer can cause both dissolution and recrystallization of the surface. − The thickness of the water condensation layer is dependent on the exposure time, temperature, RH, and the sample’s hydrophilic or hydrophobic character. ,,,− Depending on the sample, ordered hydration layers can be present. On ionic crystals, the water molecules often form ordered water layers with a characteristic structure on the sample surface. ,, The thickness of single ordered hydration layers on various samples is reported to range from 200 to 345 pm.…”

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Atomic Resolution of Calcium and Oxygen Sublattices of Calcite in Ambient Conditions by Atomic Force Microscopy Using qPlus Sensors with Sapphire Tips

et al. 2015

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Characterization and imaging at the atomic scale with atomic force microscopy in biocompatible environments is an ongoing challenge. We demonstrate atomically resolved imaging of the calcite (101̅4) surface plane using stiff quartz cantilevers ("qPlus sensors", stiffness k = 1280 N/m) equipped with sapphire tips in ambient conditions without any surface preparation. With 10 atoms in one surface unit cell, calcite has a highly complex surface structure comprising three different chemical elements (Ca, C, and O). We obtain true atomic resolution of calcite in air at relative humidity ranging from 20% to 40%, imaging atomic steps and single atomic defects. We observe a great durability of sapphire tips with their Mohs hardness of 9, only one step below diamond. Depending on the state of the sapphire tip, we resolve either the calcium or the oxygen sublattice. We determine the tip termination by comparing the experimental images with simulations and discuss the possibility of chemical tip identification in air. The main challenges for imaging arise from the presence of water layers, which form on almost all surfaces and have the potential to dissolve the crystal surface. Frequency shift versus distance spectra show the presence of at least three ordered hydration layers. The measured height of the first hydration layer corresponds well to X-ray diffraction data and molecular dynamic simulations, namely, ∼220 pm. For the following hydration layers we measure ∼380 pm for the second and third layer, ending up in a total hydration layer thickness of at least 1 nm. Understanding the influence of water layers and their structure is important for surface segregation, surface reactions including reconstructions, healing of defects, and corrosion.

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Effect of the surface water layer on the optical signal in apertureless scanning near field optical microscopy

Cited by 11 publications

References 20 publications

Optimizing atomic resolution of force microscopy in ambient conditions

Optimizing atomic resolution of force microscopy in ambient conditions

The tip–sample water bridge and light emission from scanning tunnelling microscopy

Atomic Resolution of Calcium and Oxygen Sublattices of Calcite in Ambient Conditions by Atomic Force Microscopy Using qPlus Sensors with Sapphire Tips

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