A new X-ray transmission-reflection scheme for the study of deeply buried interfaces using high-energy microbeams

Reichert, H.; Honkimäki, V.; Snigirev, A.; Engemann, S.; Dosch, H.

doi:10.1016/s0921-4526(03)00268-0

Cited by 73 publications

(53 citation statements)

References 14 publications

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“…x-ray reflectivity measurements were performed at the high-energy beamline ID15A, European Synchrotron Radiation Facility, using the surface and interface scattering instrument HEMD for high-energy microdiffraction (30). A sketch of the experimental setup is shown in Fig.…”

Section: Methodsmentioning

confidence: 99%

High-resolution in situ x-ray study of the hydrophobic gap at the water–octadecyl-trichlorosilane interface

Mezger

Reichert

Schöder

et al. 2006

Proc. Natl. Acad. Sci. U.S.A.

261

231

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The knowledge of the microscopic structure of water at interfaces is essential for the understanding of interfacial phenomena in numerous natural and technological environments. To study deeply buried liquid water-solid interfaces, high-energy x-ray reflectivity measurements have been performed. Silicon wafers, functionalized by a self-assembled monolayer of octadecyltrichlorosilane, provide strongly hydrophobic substrates. We show interfacial density profiles with angstrom resolution near the solid-liquid interface of water in contact with an octadecyltrichlorosilane layer. The experimental data provide clear evidence for the existence of a hydrophobic gap on the molecular scale with an integrated density deficit d ‫؍‬ 1.1 Å g cm ؊3 at the solid-water interface. In addition, measurements on the influence of gases (Ar, Xe, Kr, N2, O2, CO, and CO2) and HCl, dissolved in the water, have been performed. No effect on the hydrophobic water gap was found.hydrophobicity ͉ interfacial water ͉ x-ray reflectivity H ydrophobicity, i.e., the repulsion of water, is a well known phenomenon in our environment (1). The generic hydrophobic interaction occurs between a nonpolar molecule and the water molecule. In bulk water, the hydrophobic interaction leads to the so-called hydrophobic hydration of unpolar solvents which generically results in a reduced density and an increased heat capacity. The seminal study on the thermodynamics of nonpolar solvation goes back to Frank and Evans in the mid-1940s (2). While of course the details of structural ordering remained unclear, it became evident that nonpolar solvation is a negentropic process which appeared later to become a key element to understand protein folding and stability (3). The microscopic details of how the nonpolar molecules interact with each other in water is a key information to understand how proteins and biological membranes maintain their structural integrity. Today we know that hydrophobic bonds are a major force driving proper protein folding, and that the interplay between hydrophobic and hydrophilic interactions is important to stabilize the shape of biological structures, such as proteins and cell membranes (4).Hydrophobic surfaces are of particular interest, since they control many interfacial phenomena in biology and technology. However, the microscopic details of how water meets a hydrophobic interface are still not settled and in fact rather controversial. A basic missing piece of information is the size of the hydrophobic gap between the water phase and the hydrophobic surface. Wetting studies on mesoporous silica (5) indicate that water is separated from the hydrophobic walls by a vapor gap of thickness 3-4 Å. Molecular dynamics simulations carried out for liquid water between f lat hydrophobic surfaces predict density oscillations extending up to 10 Å into the adjacent water accompanied by a molecular orientational order affecting a water layer of 7 Å. The simulations, as well as the results from surface vibrational spectroscopy, show that the water mole...

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Section: Methodsmentioning

confidence: 99%

High-resolution in situ x-ray study of the hydrophobic gap at the water–octadecyl-trichlorosilane interface

Mezger

Reichert

Schöder

et al. 2006

Proc. Natl. Acad. Sci. U.S.A.

261

231

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“…This technique measures the Fourier transform of the laterally averaged electron density distribution in the surface normal direction. For a direct observation of the molecular structure of the buried interface, penetrating, high-energy x-ray beams are necessary (22). We have used beamline X-22A at the National Synchrotron Light Source of the Brookhaven National Laboratory, with an energy of 32 keV and a beam cross section of 0.1 ϫ 0.5 mm 2 .…”

Section: Resultsmentioning

confidence: 99%

Direct structural observation of a molecular junction by high-energy x-ray reflectometry

Lefenfeld

Baumert

Sloutskin

et al. 2006

Proc. Natl. Acad. Sci. U.S.A.

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We report a direct angstrom resolution measurement of the structure of a molecular-size electronic junction comprising a single (or a double) layer of alkyl-thiol and alkyl-silane molecules at the buried interface between solid silicon and liquid mercury. The high-energy synchrotron x-ray measurements reveal densely packed layers comprising roughly interface-normal molecules. The monolayer's thickness is found to be 3-4 Å larger than that of similar layers at the free surfaces of both mercury and silicon. The origins of this and the other unusual features detected are discussed in this article. Measurements of the bilayer junction with an applied potential did not show visible changes in the surface normal structure.monolayers ͉ structure ͉ x-ray reflectivity ͉ molecular electronics

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“…The chamber is developed for use on the high energy micro diffraction (HEMD) stage [5,6] at the high energy beamline (ID15) of the European Synchrotron Radiation Facility (ESRF). The HEMD setup is presented in figure 1.…”

Section: The Beamlinementioning

confidence: 99%

“…an MOCVD GaN buffer layer on 1 inch sapphire, or an ammonothermally grown 1 inch wafer) which is placed on the top heater in the chamber can act as a smooth surface on which to perform surface diffraction. A well collimated 70 keV X-ray micro-beam can then impinge the crystal from one side (see figure 5) and penetrate unrefracted down to the buried interface [5]. The reflected beam which carries information from the buried interface leaves the crystal on the other side after a full transmission and may be detected in a standard way.…”

Section: The Chambermentioning

confidence: 99%

“…However, the structure at the interface is difficult to investigate with conventional x-ray energies (E ≈10 keV) due to the attenuation by the material to be penetrated. The last two decades however, the creation of proper instrumentation [5,6] at high brilliance high-energy x-ray sources allowed scientists to start exploring these more realistic systems and more complex interfacial phenomena [7][8][9][10]. Many interfaces in crystal growth are formed in harsh conditions often combining high pressure, high temperature and dangerous gasses or liquids to form the required material.…”

Section: Introductionmentioning

confidence: 99%

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A sample chamber for in situ high-energy X-ray studies of crystal growth at deeply buried interfaces in harsh environments

Jong

Vonk

Honkimäki

et al. 2015

Journal of Crystal Growth

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We introduce a high pressure high temperature chamber for in situ synchrotron x-ray studies. The chamber design allows for in situ studies of thin film growth from solution at deeply buried interfaces in harsh environments. The temperature can be controlled between room temperature and 1073K while the pressure can be set as high as 50 bar using a variety of gases including N 2 and NH 3 . The formation of GaN on the surface of a Ga 13 Na 7 melt at 1073K and 50 bar of N 2 is presented as a performance test.

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A new X-ray transmission-reflection scheme for the study of deeply buried interfaces using high-energy microbeams

Cited by 73 publications

References 14 publications

High-resolution in situ x-ray study of the hydrophobic gap at the water–octadecyl-trichlorosilane interface

High-resolution in situ x-ray study of the hydrophobic gap at the water–octadecyl-trichlorosilane interface

Direct structural observation of a molecular junction by high-energy x-ray reflectometry

A sample chamber for in situ high-energy X-ray studies of crystal growth at deeply buried interfaces in harsh environments

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