Editing Surface science (section)

==Analysis techniques==
The study and analysis of surfaces involves both physical and chemical analysis techniques.

Several modern methods probe the topmost 1–10&nbsp;nm of [[Interface (matter)|surface]]s exposed to vacuum.  These include [[angle-resolved photoemission spectroscopy]] (ARPES), [[X-ray photoelectron spectroscopy]] (XPS), [[Auger electron spectroscopy]] (AES), [[low-energy electron diffraction]] (LEED), [[electron energy loss spectroscopy]] (EELS), [[thermal desorption spectroscopy]] (TPD), [[ion scattering spectroscopy]] (ISS), [[secondary ion mass spectrometry]], [[dual-polarization interferometry]], and other surface analysis methods included in the [[list of materials analysis methods]]. Many of these techniques require vacuum as they rely on the detection of electrons or ions emitted from the surface under study. Moreover, in general [[ultra-high vacuum]], in the range of 10<sup>−7</sup> [[pascal (unit)|pascal]] pressure or better, it is necessary to reduce surface contamination by residual gas, by reducing the number of molecules reaching the sample over a given time period. At 0.1 mPa (10<sup>−6</sup> torr) partial pressure of a contaminant and [[Standard temperature and pressure|standard temperature]], it only takes on the order of 1 second to cover a surface with a one-to-one monolayer of contaminant to surface atoms, so much lower pressures are needed for measurements. This is found by an order of magnitude estimate for the (number) [[specific surface area]] of materials and the impingement rate formula from the [[kinetic theory of gases]].

Purely optical techniques can be used to study interfaces under a wide variety of conditions.  Reflection-absorption infrared, dual polarisation interferometry, [[surface-enhanced Raman spectroscopy]] and [[sum frequency generation spectroscopy]] can be used to probe solid–vacuum as well as solid–gas, solid–liquid, and liquid–gas surfaces. [[Multi-parametric surface plasmon resonance]] works in solid–gas, solid–liquid, liquid–gas surfaces and can detect even sub-nanometer layers.<ref>{{cite journal|last1=Jussila|first1=Henri|last2=Yang|first2=He|last3=Granqvist|first3=Niko|last4=Sun|first4=Zhipei|title=Surface plasmon resonance for characterization of large-area atomic-layer graphene film|journal=Optica|date=5 February 2016|volume=3|issue=2|pages=151|doi=10.1364/OPTICA.3.000151|bibcode=2016Optic...3..151J|doi-access=free}}</ref> It probes the interaction kinetics as well as dynamic structural changes such as liposome collapse<ref>{{cite journal|last1=Granqvist|first1=Niko|last2=Yliperttula|first2=Marjo|last3=Välimäki|first3=Salla|last4=Pulkkinen|first4=Petri|last5=Tenhu|first5=Heikki|last6=Viitala|first6=Tapani|title=Control of the Morphology of Lipid Layers by Substrate Surface Chemistry|journal=Langmuir|date=18 March 2014|volume=30|issue=10|pages=2799–2809|doi=10.1021/la4046622|pmid=24564782}}</ref> or swelling of layers in different pH. Dual-polarization interferometry is used to quantify the order and disruption in birefringent thin films.<ref>
{{cite journal
 |last1=Mashaghi |first1=A
 |last2=Swann |first2=M
 |last3=Popplewell |first3=J
 |last4=Textor |first4=M
 |last5=Reimhult |first5=E
 |date=2008
 |title=Optical Anisotropy of Supported Lipid Structures Probed by Waveguide Spectroscopy and Its Application to Study of Supported Lipid Bilayer Formation Kinetics
 |journal=[[Analytical Chemistry (journal)|Analytical Chemistry]]
 |volume=80 |issue=10 |pages=3666–76
 |doi=10.1021/ac800027s
 |pmid=18422336
}}</ref> This has been used, for example, to study the formation of lipid bilayers and their interaction with membrane proteins.

Acoustic techniques, such as [[quartz crystal microbalance with dissipation monitoring]], is used for time-resolved measurements of solid–vacuum, solid–gas and solid–liquid interfaces. The method allows for analysis of molecule–surface interactions as well as structural changes and viscoelastic properties of the adlayer.  

X-ray scattering and spectroscopy techniques are also used to characterize surfaces and interfaces. While some of these measurements can be performed using [[X-ray tube|laboratory X-ray sources]], many require the high intensity and energy tunability of [[synchrotron radiation]]. [[X-ray crystal truncation rod]]s (CTR) and [[X-ray standing waves|X-ray standing wave]] (XSW) measurements probe changes in surface and [[Adsorption|adsorbate]] structures with sub-Ångström resolution. [[Surface-extended X-ray absorption fine structure]] (SEXAFS) measurements reveal the coordination structure and chemical state of adsorbates. [[Grazing-incidence small-angle scattering|Grazing-incidence small angle X-ray scattering]] (GISAXS) yields the size, shape, and orientation of [[nanoparticles]] on surfaces.<ref>{{Cite journal | doi=10.1016/j.surfrep.2009.07.002| bibcode=2009SurSR..64..255R| title=Probing surface and interface morphology with Grazing Incidence Small Angle X-Ray Scattering| year=2009| last1=Renaud| first1=Gilles| last2=Lazzari| first2=Rémi| last3=Leroy| first3=Frédéric| journal=Surface Science Reports| volume=64| issue=8| pages=255–380}}</ref> The [[crystal structure]] and [[Texture (crystalline)|texture]] of thin films can be investigated using [[Grazing incidence diffraction|grazing-incidence X-ray diffraction]] (GIXD, GIXRD).

[[X-ray photoelectron spectroscopy]] (XPS) is a standard tool for measuring the chemical states of surface species and for detecting the presence of surface contamination. Surface sensitivity is achieved by detecting [[photoelectrons]] with kinetic energies of about 10–1000 [[Electronvolt|eV]], which have corresponding [[inelastic mean free path]]s of only a few nanometers. This technique has been extended to operate at near-ambient pressures (ambient pressure XPS, AP-XPS) to probe more realistic gas–solid and liquid–solid interfaces.<ref>{{Cite journal |doi = 10.1557/mrs2007.211|title = In Situ X-Ray Photoelectron Spectroscopy Studies of Gas-Solid Interfaces at Near-Ambient Conditions|year = 2007|last1 = Bluhm|first1 = Hendrik|last2 = Hävecker|first2 = Michael|last3 = Knop-Gericke|first3 = Axel|last4 = Kiskinova|first4 = Maya|last5 = Schlögl|first5 = Robert|last6 = Salmeron|first6 = Miquel|journal = MRS Bulletin|volume = 32|issue = 12|pages = 1022–1030| s2cid=55577979 |url = https://digital.library.unt.edu/ark:/67531/metadc900709/}}</ref> Performing XPS with hard X-rays at synchrotron light sources yields photoelectrons with kinetic energies of several keV (hard X-ray photoelectron spectroscopy, HAXPES), enabling access to chemical information from buried interfaces.<ref>{{Cite journal |doi = 10.1103/PhysRevLett.102.176805|pmid = 19518810|arxiv = 0809.1917|bibcode = 2009PhRvL.102q6805S|title = Profiling the Interface Electron Gas ofLaAlO3/SrTiO3Heterostructures with Hard X-Ray Photoelectron Spectroscopy|year = 2009|last1 = Sing|first1 = M.|last2 = Berner|first2 = G.|last3 = Goß|first3 = K.|last4 = Müller|first4 = A.|last5 = Ruff|first5 = A.|last6 = Wetscherek|first6 = A.|last7 = Thiel|first7 = S.|last8 = Mannhart|first8 = J.|last9 = Pauli|first9 = S. A.|last10 = Schneider|first10 = C. W.|last11 = Willmott|first11 = P. R.|last12 = Gorgoi|first12 = M.|last13 = Schäfers|first13 = F.|last14 = Claessen|first14 = R.|journal = Physical Review Letters|volume = 102|issue = 17|pages = 176805|s2cid = 43739895}}</ref>

Modern physical analysis methods include [[scanning tunneling microscope|scanning-tunneling microscopy]] (STM) and a family of methods descended from it, including [[atomic force microscopy]] (AFM). These microscopies have considerably increased the ability of surface scientists to measure the physical structure of many  surfaces. For example, they make it possible to follow reactions at the solid–gas interface in real space, if those proceed on a time scale accessible by the instrument.<ref>{{cite journal | last1 = Wintterlin | first1 = J. | last2 = Völkening | first2 = S. | last3 = Janssens | first3 = T. V. W. | last4 = Zambelli | first4 = T. | last5 = Ertl | first5 = G. | date = 1997 | title = Atomic and Macroscopic Reaction Rates of a Surface-Catalyzed Reaction | journal = [[Science (journal)|Science]] | volume = 278 | issue = 5345 | pages = 1931–4 | doi = 10.1126/science.278.5345.1931 |bibcode = 1997Sci...278.1931W | pmid=9395392}}</ref><ref>{{cite journal | last1 = Waldmann | first1 = T. | display-authors = etal   | date = 2012 | title = Oxidation of an Organic Adlayer: A Bird's Eye View | journal = [[Journal of the American Chemical Society]] | volume = 134 | issue = 21 | pages = 8817–8822 | doi = 10.1021/ja302593v | pmid=22571820}}</ref>