The Effect of Illumination on the Contact Angles of Pure Water on Amorphous Silicon

Vera‐Graziano, Ricardo; Mühl, S.; Rivera-Torres, Filiberto

doi:10.1006/jcis.1993.1047

Cited by 4 publications

(4 citation statements)

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“…Note that the bulk refractive indices are still applicable until the coating thickness exceeds ten nm 23 , 24 . We can assume that the thickness of the PDMS layer is 1–2 nm for all the tips in this experiment because the three tip materials have a similar hydrophobicity 16 , 25 , 26 . Since the PtSi-coated tip has the highest refractive index and a relatively small tip radius compared to the other tips, the PiFM spectrum measured with a PtSi-coated tip shows the strongest signal, as expected.…”

Section: Resultsmentioning

confidence: 99%

Substructure imaging of heterogeneous nanomaterials with enhanced refractive index contrast by using a functionalized tip in photoinduced force microscopy

Jahng

Lee

2018

Light Sci Appl

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The opto-mechanical force response from light-illuminated nanoscale materials has been exploited in many tip-based imaging applications to characterize various heterogeneous nanostructures. Such a force can have two origins: thermal expansion and induced dipoles. The thermal expansion reflects the absorption of the material, which enables one to chemically characterize a material at the absorption resonance. The induced dipole interaction reflects the local refractive indices of the material underneath the tip, which is useful to characterize a material in the spectral region where no absorption resonance occurs, as in the infrared (IR)-inactive region. Unfortunately, the dipole force is relatively small, and the contrast is rarely discernible for most organic materials and biomaterials, which only show a small difference in refractive indices for their components. In this letter, we demonstrate that refractive index contrast can be greatly enhanced with the assistance of a functionalized tip. With the enhanced contrast, we can visualize the substructure of heterogeneous biomaterials, such as a polyacrylonitrile-nanocrystalline cellulose (PAN-NCC) nanofiber. From substructural visualization, we address the issue of the tensile strength of PAN-NCC fibers fabricated by several different mixing methods. Our understanding from the present study will open up a new opportunity to provide enhanced sensitivity for substructure mapping of nanobiomaterials, as well as local field mapping of photonic devices, such as surface polaritons on semiconductors, metals and van der Waals materials.

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Section: Resultsmentioning

confidence: 99%

Substructure imaging of heterogeneous nanomaterials with enhanced refractive index contrast by using a functionalized tip in photoinduced force microscopy

Jahng

Lee

2018

Light Sci Appl

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“…The literature contains many studies concerning the static wetting of smooth silicon surfaces − and physically modified (e.g., patterned and structured) silicon surfaces; − in contrast, the literature is somewhat sparse in terms of dynamic wetting on silicon. A very thin silicon oxide layer is known to play a key role in wetting, as is a hydrogen-terminated silicon surface resulting from the exposure of crystalline silicon to hydrofluoric acid (HF) solutions .…”

Section: Introductionmentioning

confidence: 99%

“…Hermansson et al and Backlund et al showed that the static wetting contact angle of a droplet depends on the specific chemical treatment of the silicon. Vera-Graziano et al demonstrated that the wetting of bare silicon surfaces is dependent on illumination. Sata and Maeda showed that the wetting of pure water on crystalline silicon is dependent on the impurity doping density and orientation.…”

Section: Introductionmentioning

confidence: 99%

Dynamic Chemically Driven Dewetting, Spreading, and Self-Running of Sessile Droplets on Crystalline Silicon

Arscott

2016

Langmuir

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A chemically driven dewetting effect is demonstrated using sessile droplets of dilute hydrofluoric acid on chemically oxidized silicon wafers. The dewetting occurs as the thin oxide is slowly etched by the droplet and replaced by a hydrogen-terminated surface; the result of this is a gradual increase in the contact angle of the droplet with time. The time-varying work of adhesion is calculated from the time-varying contact angle; this corresponds to the changing chemical nature of the surface during dewetting and can be modeled by the well-known logistic (sigmoid) function often used for the modeling of restricted growth, in this case, the transition from an oxidized surface to a hydrogen-terminated silicon surface. The observation of the time-varying contact angle allows one to both measure the etch rate of the silicon oxide and estimate the hydrogenation rate as a function of HF concentration and wafer type. In addition to this, at a certain HF concentration, a self-running droplet effect is observed. In contrast, on hydrogen-terminated silicon wafers, a chemically induced spreading effect is observed using sessile droplets of nitric acid. The droplet spreading can also be modeled using a logistical function, where the restricted growth is the transition from hydrogen-terminated to a chemically induced oxidized silicon surface. The chemically driven dewetting and spreading observed here add to the methods available to study dynamic wetting (e.g., the moving three-phase contact line) of sessile droplets on surfaces. By slowing down chemical kinetics of the wetting, one is able to record the changing profile of the sessile droplet with time and gather information concerning the time-varying surface chemistry. The data also indicates a chemical interface hysteresis (CIH) that is compared to contact angle hysteresis (CAH). The approach can also be used to study the chemical etching and deposition behavior of thin films using liquids by monitoring the macroscopic droplet profile and relating this to the time-varying physical and chemical interface phenomena.

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“…Furthermore, contact angles are easily measured and a good reproducibility has been obtained in different studies with a variety of materials and systems. in the contact angles can be related to electromagnetically active non-uniformities in the solid surface [2]. Semiconductor materials present an additional parameter which can modify the contact angle: the so-called photovoltaic effect.…”

Section: Introductionmentioning

confidence: 99%

Illumination-induced surface charges on thin diamond films at different wavelengths

Apátiga

Alba

Castaño

et al. 1996

J Mater Sci: Mater Electron

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Contact angle studies of pure water droplets were carried out on thin diamond films. The films were deposited on a fresh Si <1 1 1) wafer by plasma assisted chemical vapour deposition (PACVD) and confirmed to be diamond by Raman spectroscopy and scanning electron microscopy. Advancing and receding contact angles were measured as a function of droplet volume by using different incident wavelengths: red, green and violet. Large differences in the contact angles were observed, depending on the wavelength of the incident light. These differences are usually related to the existence of illumination-induced surface charges or electromagnetically active inhomogeneities in the diamond films. The results show that this technique is sufficiently sensitive to correlate changes in the contact angle with changes in the wavelength used.

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The Effect of Illumination on the Contact Angles of Pure Water on Amorphous Silicon

Cited by 4 publications

References 0 publications

Substructure imaging of heterogeneous nanomaterials with enhanced refractive index contrast by using a functionalized tip in photoinduced force microscopy

Substructure imaging of heterogeneous nanomaterials with enhanced refractive index contrast by using a functionalized tip in photoinduced force microscopy

Dynamic Chemically Driven Dewetting, Spreading, and Self-Running of Sessile Droplets on Crystalline Silicon

Illumination-induced surface charges on thin diamond films at different wavelengths

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