Compendium of Surface and Interface Analysis

Biological ultrasonic microscopy, also known as biological scanning acoustic microscope, provides quantitative acoustic parameters like sound speed and characteristic acoustic impedance that are relevant to elastic properties.

STM-AS is a spectroscopic method capable of vibrational analysis of individual adsorbates on surfaces.

X-ray photoelectron spectroscopy (XPS) is one of most thoroughly used surface science techniques, which provides information on chemical states of both adsorbates and substrates on the basis of core-level shifts of photoelectrons excited primarily with X-rays.

ARUPS enables us to determine experimentally the electronic band structure and Fermi surface of crystals.

A high electric field of greater than 0.5 V/Å can be generated over the apex of a sharpened metallic needle (tip) with a radius of less than 100 nm, by application of a voltage of higher than a few kV to the tip.

AFM was developed to overcome a drawback of scanning tunneling microscopy (STM), which can only image conducting surfaces.

As each element carries unique values of core-level binding energies, E_C, this has enabled the development of numerous elemental composition analysis methods based on core electron excitation.

Cathodoluminescence is a light emission according to an electron beam injection.

In CAFM mode as shown in Fig. 9.1, which is based on contact mode, a bias voltage is applied during scanning between the probe and the sample, the current that flows is detected, and images of the in-plane distribution are created at the same time as images of the shape. Moreover, this system can evaluate electrical properties of the sample surface by I/V measurement function which can measure the current between the probe and the sample while sweeping the sample bias voltage.

A specimen that has an even magnitude of reflectivity all over the surface is called a phase object.

Ion beam bombardment with energy of less than a few tens of kiloelectron volts (primary ion bombardment) onto the sample surface causes sputtering phenomena following cascade mixing in the near-surface of the sample.

ERDA is a complementary method to RBS. While RBS is a way sensitive to heavy elements, ERDA is effective to quantify light elements, particularly for hydrogen.

Atomic force microscopy (AFM) can image the surfaces of flat materials, irrespective of their conductivity. The sample is usually imaged in air, but can be in liquid environments and under vacuum, as described in other chapters (Chaps. 6, and 55). AFM has also been applied to the electrode/electrolyte interfaces, since its invention.

As an application of infrared reflection absorption spectroscopy (IRAS) in the electrochemistry, electrochemical infrared spectroscopy (EC-IR) is becoming a routing technique to study the chemical structures on the electrode and solution interface during the electrochemical reactions.

EC-STM directly visualizes atomic structures of solid surfaces and a variety of adsorbates thereon in electrolyte solutions. The working principle is based on electron tunneling, being the same as STM: the tunneling current flowing between the sample surface and atomically sharp tip is probed.

EC-SHG is an application of SHG to electrochemical interfaces. As has been described, SHG is a photon-in-photon-out process and can be applied to any kind of interfaces: liquid/solid, liquid/liquid, and solid/solid. The phenomenon is known as the conversion of two photons with the fundamental frequency, ω, in one photon with the second harmonic (SH) frequency, 2ω. Since the SH signal generated from both the several atomic or molecular layers at usual centrosymmetric electrode/electrolyte interfaces, the SH signal is inherently sensitive to interfacial parameters, such as charge density, adsorbate coverage, atomic orientation, and electronic structure around Fermi level. At electrochemical interfaces, electrolyte solution covering the electrode surfaces limits the application of electron spectroscopy, such as UPS and EELS.

Since the surface is buried in liquid, electrochemical surface science is complicated. Therefore, one cannot benefit from the electron-based techniques mainly used in ultra-high vacuum (UHV) to study the structure and composition of surfaces since the mean free path of the electrons in dense media, i.e., water, is rather limited.

Electrochemical surface X-ray scattering (EC-SXS) is an application of surface X-ray scattering (SXS) technique, one of the surface analysis methods, to electrochemical interfaces, i.e., electrode/electrolyte solution interfaces.

Electrochemical transmission electron microscopy (ECTEM) is one of in-situ TEM observation methods. It enables us to visualize local structure and/or composition change at the interface between a solid electrode and a liquid electrolyte during the electrochemical process.

In the present chapter, utilization of XAFS to the electrochemical interfaces is briefly introduced.

Although X-ray photoelectron spectroscopy (XPS) requires a vacuum (Chap. 132 X-ray Photoelectron Spectroscopy), in situ electrochemical (EC-) XPS has been a long-standing dream not only for fundamental science, but also for a wide range of applications including fuel cells, rechargeable batteries, photocatalysts, and biological processes. In the present chapter, various in situ EC-XPS systems are introduced.

Electron backscatter diffraction patterns (EBSD patterns) can be used to determine the orientation of the crystal lattice. Principle of EBSD pattern is similar to Kikuchi pattern observed in transmission electron microscope (TEM). In the case of scanning electron microscope (SEM), when an electron beam enters a highly tilted crystalline material, it is inelastically scattered in all directions.

Fast electrons traveling with kinetic energy in the range from tens to hundreds of kilo-electron volts penetrate nanometer-scale objects and can probe both interior and surface portions of the nanomaterials. The traveling electrons interact with ion cores and electrons in the material and are scattered out from the sample with or without changing their kinetic energies.

When an accelerated electron strikes a substance, it sometimes ejects the inner shell electron of the atom existing in the substance and creates a vacancy. This phenomenon is called electron beam excitation.

Bonding states between adsorbates and a solid surface are electronically excited by irradiation of photons or electrons to the surface, and subsequently, as a result of the relaxation processes, adsorbates are released as ions or neutral particles having kinetic energy of a few eV. Such particle release is generally referred to as desorption-induced electronic transition (DIET).

If we irradiate an electron beam onto a semiconductor, electrons and holes are generated within the volume where e-beam reaches. The generated carriers undergo diffusion and recombination to reach a new equilibrium. If there exists an electric field such as Schottky contact or p-n junction, the excess electrons and holes are collected by this field.

In general, since the amplitude and phase are different between the p- and s-polarizations of the reflected light, the reflected light is elliptically polarized. Ellipsometry precisely measures the shape of reflection ellipse by irradiating totally polarized light to a planer bulk surface, a thin film, and a multilayer.

Conventional SEM normally has vacuum environment between electron optic column and specimen chamber so that electron beam-emitted electron source travels to specimen without being scattered by gas molecular.

ETEM is a dynamic observation technique based on transmission electron microscopy (TEM).

Extended X-ray absorption fine structure (EXAFS) is a part of X-ray absorption spectroscopy methods to observe local structures of elements of interest.

Focused ion beam is rather a new type of ion beam. Its prominent feature is fine focusing ability around 100–10 nm.

The basis of the force curve measurement is the measurement performed at one point of the sample.

Using atomic force microscopy (AFM) in force spectroscopy (FS) mode is a powerful tool to study the fundamental surface, physicochemical and biological forces between an AFM tip and a surface, molecule or living cell of interest.

Frequency-Modulation atomic force microscopy (FM-AFM), one of the AFM modes, can image surface single atoms and molecules. Different from scanning tunneling microscopy (STM) that has also atomic resolution, FM-AFM can be operated on the insulator surface. Force spectroscopy using FM-AFM measures chemical bonding force between atoms of the AFM tip and sample surface.

Proximity of a metal nanoparticle to a planar metal surface can induce SERS effect through excitation of gap-mode plasmons. This allows us to observe atomically defined metal surfaces, which is never expected in conventional SERS.

Glow discharge mass spectrometry (GDMS) is a very sensitive technique to analyze elements in solid samples using glow discharge plasma. Samples serve as the cathode, and discharge cells serve as the anode.

GDOES [1] is a spectrochemical technique that allows direct in-depth determination of major and trace elements. In GDOES a pulsed radio frequency

Hard X-ray photoelectron spectroscopy (HAXPES) is a kind of X-ray photoelectron spectroscopy (XPS), photoelectron spectroscopy by use of a higher-energy excitation (from synchrotron radiation, in most cases) than a conventional

HAS provides information about the outermost surface structure, phonon dispersion curve, and lattice dynamics of a material by measuring the angular intensity distribution and/or energy of helium beam scattered from the sample surface.

HERDA is an advanced type of Elastic Recoil Detection Analysis (ERDA), depth resolution of which is improved. Figure 40.1 shows a schematic illustration of HERDA. In HERDA, as in a conventional ERDA, a well-collimated beam of monoenergetic He or heavier ions is incident on a solid sample.Fig. 40.1Schematic illustration of HERDA

High-resolution electron energy loss spectroscopy (HREELS) is used to study normal vibrational modes of molecules on the surface or vibrations of the surface (surface phonon) under ultra-high vacuum conditions.

High-resolution Rutherford backscattering spectrometry (HRBS) is an advanced type of Rutherford backscattering spectrometry (RBS), depth resolution of which is improved to sub-nm.

The basic principle of high-speed atomic force microscopy (HS-AFM) is similar to a conventional AFM in which force interactions between a sharp needle at the end of a cantilever and a solid surface is detected through the deflection of the cantilever (Binnig et al. Phys Rev Let 56:930–933, 1986 [1]).

The measured signals in imaging ellipsometry are the change in polarization as the incident radiation interacts with the material structure of interest at each point on the surface.

Ion scattering spectroscopy (ISS) (Smith in J Appl Phys 38:340–347, 1967 [1]) is a real-space method that enables simultaneous analysis of the composition and structure of solid surfaces by utilizing elastic scattering of ions at the surfaces.

Inelastic electron tunneling spectroscopy (IETS) is a vibrational spectroscopy method.

Infrared (IR) spectrometry is a representative un-destructive spectroscopic analytical technique, which provides rich molecular information such as molecular conformation, polymorph, packing and orientation. Another significant benefit of using IR spectroscopy is the sensitivity, which is good enough for analyzing monolayer-level thin films. Considering the great quantitative reproducibility, IR spectroscopy is one of the first choices to analyze an ultrathin film particularly of an organic compound. Here, IR reflection spectrometry on a nonmetallic surface, which is called “external reflection,” is described.

Infrared reflection–absorption spectroscopy (IRAS) is a spectroscopic method for measuring an infrared reflection absorption spectrum due to vibrations of adsorbed atoms and molecules (Hoffmann in Surf. Sci. Rep. 3: 107, 1983 [1]; Chabal in Surf. Sci. Rep. 8: 21, 1988 [2]; Bradshaw and Schweizer in Adv. Spectrosc. 16: 413, 1988 [3]; Madey and Yates (ed.) in Vibrational Spectroscopy of Molecules on Surfaces (Methods of Surface Characterization). Springer, 1987. [4]), where infrared light is incident to an optically flat metal surface at a grazing angle and reflected light is detected.

The displacement measurement using optical interferometry is based on the observation of an interferogram caused by interfering two reflected lights from a sample surface and a reference mirror surface.

Inverse photoemission spectroscopy (IPES) is a technique that probes unoccupied electronic states between the Fermi level (E_F) and the vacuum level of a material Woodruff et al. (J. Vac. Sci. Technol., A 1:1104–1110, 1983 [1]).

KPFM mode as shown in Fig. 51.1 generates images based on the electric potential of the sample surface. Applying an AC voltage to a conductive cantilever and detecting the resulting electric force makes it possible to observe the surface profile and, at the same time, the surface potential distribution.

Laser SNMS is a mass-selective surface imaging technique based on photo-ionization of sputtered neutrals originated in an ion beam irradiation on a solid sample. Atoms, occasionally molecules, are promoted and ionized through photon absorption.

Photoemission spectroscopy is an extensively used technique to investigate the electronic characteristics of solid surfaces. In this decade, laser photoemission spectroscopy [1], in which a laser is used as the excitation light source instead of a helium discharge lamp and/or synchrotron light source, has been developed. Lasers offer many advantages over these conventional light sources, such as strong intensity, coherency, ultranarrow linewidth (or ultrashort pulse duration), and high tunability of polarization.

In lateral force microscopy, not only the topographic image of the sample surface but also the distribution image of the lateral force in the same area can be gotten simultaneously.

The principle of liquid SPM/AFM is the same as atmospheric AFM (Fig. 55.1). When a probe is near or in contact with a sample surface, an image of the probe–sample interaction with atomic resolution can be obtained. The difference between atmospheric observations and liquid SPM/AFM is that the probe and sample are immersed in a solution.

Low-energy ions scattering (less than 5 keV) is a powerful tool for the analysis of “first monolayer”.

Low-energy electron diffraction (LEED) [1] is one of the diffraction techniques utilizing low-energy electrons and a powerful method for surface structural analysis.

Low-energy electron microscopy (LEEM) is a projection-type microscopy technique collecting low-energy (typically 1–100 eV) electrons backscattered from the samples for imaging [1].

Magnetic force microscope (MFM) is one of the SPM families which can visualize the leakage magnetic field by detecting the magnetic force between a probe and a sample.

Matrix-assisted laser desorption/ionization (MALDI) is a “soft” ionization technique commonly used in mass spectrometry (Fig. 60.1). It uses organic compounds (typically an organic acid) called “matrix” as a means of facilitating desorption and ionization efficiency.

Medium-energy ion scattering is a method to analyze energy of large-angle scattered ions from a sample using hydrogen or helium ion beam accelerated to about several hundred keV. Fast ions gradually lose their energy mainly due to interaction with electrons in the solid, and only a small portion of the incident ions are scattered in large angle by close collisions between the nuclei.

Raman scattering is an inelastic light scattering, with which molecular or lattice vibration is excited by accepting a part of light energy incident to a material. Since the molecule/lattice vibration is determined by the molecular/lattice structure in the material, measuring the energy loss of light (photon) provides the information of the molecule/lattice vibration excited.

Microprobe reflection high-energy electron diffraction (μ-RHEED) is a reflection high-energy electron diffraction (RHEED) that uses focused electron beams with about 10 nm diameter. The focused electron beams with higher than 10 keV kinetic energy are irradiated on sample surfaces at grazing angles less than 5° to get RHEED patterns from the sample surface nanoareas and analyze their crystallinities.

Multiple-probe scanning probe microscope (MP-SPM) was developed to overcome difficulties in characterizing physical properties of nanoscale structures and materials with conventional SPM families, such as a scanning tunneling microscope (STM), an atomic force microscope (AFM), and the related proximal probe microscopes.

Photoelectron spectroscopy or electron spectroscopy for chemical analysis (ESCA) is a powerful technique for investigating the electronic structure of solid surfaces. From the angular distribution of valence band photoelectron spectra, we can obtain the dispersion of valence bands in the reciprocal space of solids. This technique is called angle-resolved photoemission spectroscopy (ARPES). On the other hand, the angular distribution of core-level photoelectron spectra corresponds to the probing depth dependence of the photoelectron spectra and can be converted into the depth profiling information.

Various techniques of nonlinear spectroscopy are now applied to surface and interface analyses. They include sum frequency generation (SFG) and second-harmonic generation (SHG) that are detailed in other sections. SFG provides rich information on molecular structure at an interface by virtue of vibrational spectra, but it is not applicable to buried interfaces sandwiched by dense media absorbing IR light strongly. SHG has wider applicability because it does not use IR but just UV or visible light, but it does not allow for recording vibrational spectra. This section introduces fourth-order nonlinear Raman (FR) spectroscopy that has the advantages of SFG and SHG simultaneously.

Nuclear reaction analysis is a method to quantitatively determine the concentration versus depth distribution of light elements in the near-surface region of solids. To detect a specific nucleus A, the analyzed material is bombarded with a beam of projectile ions (a) at a high energy (100 keV–20 MeV) that is sufficient to overcome the Coulomb repulsion barrier to fuse the nuclei of a and A. Conserving the total energy, the resulting nuclear reaction A(a,b)B forms a new nucleus B and emits secondary particles (b: protons (p), neutrons (n), 4He ions (‘α particles’) and/or γ-photons) with well-defined high (keV-MeV) energies. The presence of nucleus A in the target is then proven by registering such secondary particles (b) or the reaction product (B) with a suitable detector.

Major types of optical microscopes include bright field microscopes, dark field microscopes, fluorescence microscopes, phase-contrast microscopes, and differential interference microscopes. Such microscopes have characteristics and features that are unique in terms of the light emitted or absorbed by an object to be observed. For example, a fluorescence microscope distinguishes differences in structure by detecting the concentration distribution of a fluorescent substance or in the fluorescence spectrum when the object emits fluorescence. Bright and dark field microscopes distinguish the target of observation from other objects based on the absorption/reflection and scattering of light, respectively. All of these microscopes have to condense the light from the objects with lenses.

When the incident light irradiates the surface or interface of a material, two photons with the same photon energy ћω interact with the material together and generate one new photon with the doubled photon energy of 2ћω, as shown in Fig. 69.1a.

PIXE was first proposed by Sven Johansson in 1970 [1]. This method of analysis is based on the emission of characteristic X-rays from a sample after inner-shell ionization with ions from accelerators. In comparison to other analytical techniques based on X-ray spectrometry, such as EPMA and XRF, the ion beams generate fewer continuous X-rays, which dwarf the trace element peaks. Thus, it has an excellent sensitivity down to the ppm level for solids and the ppb level for liquids.

Penning ionization electron spectroscopy (PIES) is based on the Penning ionization (PI) phenomenon caused by the interaction between excited metastable atoms and semiconducting or insulating surfaces (Fig. 71.1) [1]. When the excited metastable atoms, typically excited helium atoms in the triplet state [He*(23S; 19.82 eV)], approach the material surface, the valence band electron of the materials (Φ_A, Φ_B, …) transfers to the 1s level of the metastable atom (χ_a) via tunneling. According to the energy conservation law, the energy loss of the transferred valence electron is subsequently used for the electron emission from the 2s level (χ_b) in the He* atoms, providing the information of spatial distribution and binding energy of the targeted atomic orbitals (AOs) or molecular orbitals (MOs).

If the cantilever is vibrated at a constant amplitude and frequency (near the resonance frequency of the cantilever) and lightly pressed against the sample, the amplitude and phase will change with a correlation with the shape and physical properties of the sample surface [1]. The method of detecting and imaging the amplitude and phase change of the cantilever at this time is called Phase Mode. Especially in the phase image, images that are not mere surface shapes can be obtained.

The discontinuity of bulk properties at material surfaces and interfaces can give rise to various useful functionalities. The visualization of the three-dimensional atomic arrangement of such structures is essential in materials science and engineering. Photoelectron diffraction (PED) is an element-selective method for local surface structure analysis [1].

Optical holograms are widely used in our daily life. Three-dimensional structural information is recorded in an optical hologram based on the wave nature of light, and we can see the 3D image on the hologram. Similarly, 3D atomic arrangements can be recorded using the electron wave. When an atom is excited with an X-ray, a photoelectron is emitted. The photoelectron from a localized core level is an excellent element-specific probe for the analysis of atomic structure. Information on the photoelectron-emitting atom and the surrounding atomic configuration is recorded as a photoelectron hologram in the photoelectron intensity angular distribution (Szöke et al. in AIP Conf Proc 147, 361–367 1986 [1]). Photoelectron holography is a technique for deriving real-space atomic structures from photoelectron diffraction.

PYS is a method to measure the ionization energy of materials (work function in the case of metals) by using photoemission process. A sample surface is irradiated by tunable UV light, and the number of emitted photoelectrons is measured. The quantum yield of photoelectron (Y), which is the number of emitted photoelectrons per photon absorbed, is detected as a function of incident photon energy (hν). The principle is shown in Fig. 75.1 for the case of a material with an energy gap. When hν becomes greater than the threshold ionization energy (I_th) during incremental hν scan, the value of Y starts to increase. Thus, by determining the threshold of the spectrum, the value of I_th can be evaluated. In the case of metal sample, the work function of the sample can be deduced in the similar way.

PEEM is one of the imaging type photoelectron microscopy (Kinoshita et al. in J Phys Soc Jpn 82 2013 [1]). The apparatus is equipped with some electrostatic lens systems, a microchannel plate (MCP) and a fluorescent screen. When excitation photons are injected onto a sample, photoelectrons including secondary electrons are emitted. The lens systems magnify and focus the images of spatial distributions of these electrons from the sample onto the MCP. Then the screen is illuminated by these amplified electrons. By using a charge coupled device (CCD) camera, a magnified image of the emitted electron distributions from the sample surface can be obtained. When a mercury lamp or a deuterium lamp is used as an excitation source, the distribution of the local work function of the surface becomes visible, since the photon energy is about 4 eV.

Spontaneous emission (radiation) of light from an electronically excited material (except for thermal radiation) is called “luminescence.” In particular, photoluminescence (PL) is light emission occurring after absorption of shorter-wavelength light (higher-energy photons) (Fox in Optical properties of solids. Oxford University Press Inc 2001 [1]). In a typical direct-gap semiconductor, electrons (solid circles) and holes (open circles) that are optically excited into conduction and valence bands, respectively, first relax to lower available energy levels by emitting multiple low-energy phonons and then relax to the ground state by recombination and emission of a photon (Fig. 77.1, E_Laser and E_PL are the excitation and emission photon energies, respectively). Since the photoexcited electron and hole are oppositely charged, they can attract each other through mutual Coulomb interaction and form a hydrogen-like electron–hole pair called an “exciton.”

Photon emission from a scanning tunneling microscope (STM) is based on photon creation due to inelastic scattering of electrons tunneling from a STM tip through the tunneling gap under the application of bias voltage.

Photo-stimulated desorption (PSD) is desorption of adsorbed molecules from surfaces induced by photon irradiation. PSD occurs either in thermal or nonthermal ways. In the former case, the energy of light absorbed by solid surfaces is converted to heat, leading to the thermally activated desorption, where the desorbed molecules are in thermal equilibrium with the surface at a certain temperature. In the latter case, on the other hand, the photo-excitation is classified into two regimes, phonon excitation and electronic excitation of the adsorbate-surface complex depending on the photon energy. The absorbed light energy is transferred to the adsorbate through phonon–phonon or electron–phonon interaction, which eventually leads to breaking of the adsorbate-surface bond. In the case of electronic excitation, the excitation is further classified into either core electron or valence electron excitation.

Ferroelectric material generates an electric charge when pressure is applied. Also, it will expand and contract when a voltage is applied. In Piezoresponse Force Microscope (PFM), a conductive cantilever is used to apply a voltage to a local region of a ferroelectric material, and distortion caused by the piezoelectric effect of the ferroelectric material is detected as a deflection of the cantilever and imaged (Gruverman in Appl Phys Lett 69:3191–3193, 1996 [1]). In the measurement, the polarized state of the sample is measured with respect to the AC voltage applied between the sample and the probe by whether the relationship between expansion and contraction of the sample strain is in-phase or reversed (Fig. 80.1). Piezoelectric response of ferroelectric material of nm order can be detected. PFM is a useful technique for local polarization/phase transition of ferroelectric material, observation of domain boundary, and so on.

PAID refers to ion desorption from solid surfaces initiated by ionization of surface atoms via electron–positron pair annihilation. It occurs even if the kinetic energy of incident positrons is lower than the threshold energies for electron-stimulated desorption (ESD) of ions initiated by electron-impact excitation of surface atoms.

Multiple-angle incidence resolution spectrometry (MAIRS) is a unique technique built on a chemometric idea to simultaneously reveal the TO and LO energy-loss function spectra (see Chapter 47) of an identical thin film sample deposited on an infrared (IR) transparent substrate (Hasegawa in J Phys Chem B 16:4112–4115 2002 [1]). To prevent the polarization dependence of FT-IR, an improved technique of pMAIRS is developed, which employs only p-polarization. pMAIRS is now becoming a promising technique for quantitative molecular orientation analysis in a thin film (Hasegawa in Anal Chem 79:4385–4389 2007 [2]). Here, only the pMAIRS technique is described.

A quartz crystal microbalance (QCM) is an acoustic transducer that converts mass changes on the sensor surface of an oscillating quartz-crystal resonator into an electronic signal.

Reflectance difference spectroscopy (RDS) is a linear optical method capable of performing highly sensitive measurements to the reflectance anisotropy (RA) of solid surfaces, providing information on the surface structure and electronic states near the surface (Shudo et al. in Frontiers in optical methods: nano-characterization and coherent control. Springer-Verlag GmbH, Berlin/Heidelberg, 2013, Weightman et al. in Rep Prog Phys 68:1251, 2005 [1, 2]).

Reflection High-Energy Electron Diffraction (RHEED) (Ichimiya and Cohen in Reflection high-energy electron diffraction, Cambridge University Press, Cambridge, 2004 [1]) is one of the powerful methods for surface structural analysis.

In the RIXS process, a core electron of a particular element is resonantly excited to an unoccupied state by a monochromatized incident X-ray, which is a process called X-ray absorption (XAS).

RBS is a method to determine the absolute elemental composition, usually of thin films (t ~ several tens or hundreds nm) deposited on substrates.

As shown in Fig. 88.1, a very small MOS (metal–oxide–silicon) structure is formed by contacting the metallic tip of the AFM (Atomic Force Microscopy) to the oxide surface of the silicon sample.

Scanning electrochemical microscopy (SECM) is a probe microscopy technique in which an ultramicroelectrode (UME) is used as a probe.

SEM-EDS performs an elemental analysis on a material’s surface. The high-energy electron beam of the scanning electron microscope (SEM) interacts with the sample material and a characteristic X-ray is generated. Energy-dispersive X-ray spectrometer (EDS, EDXS) then detects the characteristic X-ray.

Scanning electron microscope (SEM) is an instrument that can image and analyze specimens using a focused electron beam. When the focused electron beam irradiates a specimen, various signals are generated in consequence of the interaction of the incident electron with atoms in the specimen (Fig. 91.1) (Reimer in Scanning electron microscopy: physics of image formation and microanalysis. Springer Verlag, 1998 [1]). Among the signals generated from the surface of the specimen, secondary electrons (SEs) and backscattered electrons (BSEs) can be detected for observation of shape and composition (material contrast).

Scanning helium ion microscope (SHIM) is based on the similar principle with field emission scanning electron microscope (FE-SEM) (Guo in Scanning Helium Ion Microscopy, Characterization of Materials. Wiley, pp. 1–9, 2012 [1]). The difference between them is that scanning beam of SHIM is a positively charged helium ion (He+) beam from a gas field ion source (GFIS), but not a negatively charged electron beam. An enlarged image of the sample surface is obtained like FE-SEM. Helium gas is field-ionized almost only from the top-most atoms by applying a high voltage to a sharp tip made of monocrystalline refractory metals in a diluted helium gas. Only the He+ beam emitted from a single atom is focused by the ion optical system and is scanned over the sample surfaces. If a backscattered ion detector is equipped, the secondary electrons (SE) and backscattered ions (BSI) can be acquired simultaneously. SHIM can observe the sample image with less current than FE-SEM. If the neutralizing flood gun is equipped, it is easier to observe insulating materials than FE-SEM. SHIM can also be used for direct nanofabrication like focused ion beam (FIB) systems. Since He+ beam does not have such a sputtering capability as a gallium ion beam, it cannot process on the micron-scale, but nanoscale ultrafine modification utilizing the nanoscale-focused He+ beam is possible. If a gas introduction system is installed, deposition of gas-decomposition microstructures by a precisely controlled He+ beam is possible

Scanning near-field optical microscopy (SNOM)/near-field scanning optical microscopy (NSOM) is one of the scanning probe microscopies, especially for investigation of optical properties and phenomena in nanometer scale. SNOM/NSOM observation provides high spatial resolution of 10–100 nm that conventional optical microscopes do not achieve, in principle.

Scanning probe microscopy (SPM) is a kind of microscopy that generates images of surface features by mechanically scanning a physical probe over the specimen under study, in which the concomitant response of a detector is measured. This generic term encompasses STM, SFM, SNOM, SCM, SKPM, SICM, etc., where “X” of SXM denotes interactions between the probe and the specimen. For instance, “T” of STM expresses “tunneling current” and “F” of SFM “force.” Depending on the detail of interaction force, SFM has more specific commonly used names such as AFM (atomic force), MFM (magnetic force), and FFM (friction force). The resolution of each SPM varies somewhat with a kind of interaction, but some reach an atomic resolution. The nature of an SPM probe depends on the type of SPM being used. However, certain characteristics are common to all SPMs: the probe must have a very sharp apex to realize high-resolution feature.

Scanning transmission electron microscopy (STEM) (Pennycook, Nellist in Scanning Transmission Electron Microscopy, Imaging and Analysis. Springer, New York, 2011 [1]; Tanaka in Scanning Transmission Electron Microscopy of Nanomaterials. Imperial College Press, London, 2015 [2]) is a method of observing a small area using an incident electron probe, which is scanned on a thin specimen (Fig. 95.1). Various electron signals from the specimen, including transmitted electrons, diffracted electrons, thermal diffuse scattered electrons, and secondary electrons, are simultaneously measured as a function of the position of the incident electron probe, resulting in two-dimensional STEM images. Bright-field (BF), annular BF, and annular dark-field (ADF) imaging are normally applied. The spatial resolution of STEM images basically depends on the size of the incident probe, and atomic resolution has already been realized. STEM combined with analytical techniques, such as energy-dispersive X-ray spectroscopy (EDX) and electron energy-loss spectroscopy (EELS), allows us to perform chemical analyses with a high spatial resolution.

Scanning transmission X-ray microscopy (STXM) is a method to obtain a microscopic image of the raster-scanned sample by detecting the transmission intensity of the focused X-rays. As drawn in Fig. 96.1, a Fresnel zone plate (FZP) is often used to focus the soft X-rays from the synchrotron radiation sources (Attwood in Soft X-rays and Extreme Ultraviolet Radiation: Principles and Applications. Cambridge University Press, 1999 [1]). An order-sorting aperture (OSA) is used to omit the zeroth and higher order diffractions. The photon energy can be tuned around the absorption edge of a specific element. The spatial resolution, i.e. the focusing size of the X-rays in the soft X-ray STXM is typically 20–100 nm. It is in principle determined by the diffraction limit of the lithographically fabricated FZPs (Attwood in Soft X-rays and Extreme Ultraviolet Radiation: Principles and Applications. Cambridge University Press, 1999 [1]). The most important measurement mode in the STXM is an “image stack,” that is, a number of images at different photon energy points to obtain a dataset with space (XY) plus energy (E) dimensions. From the dataset, one can obtain a local spectrum to analyze the near-edge X-ray absorption fine structure (NEXAFS).

STM is a surface microscope with extremely high spatial resolution, which enables us to see atoms on surfaces. When a sharp metal needle is located at a very proximate distance (~1 nm) from the sample surface (left panel in Fig. 97.1), tiny amount of electrical flow, called a tunneling current, is induced between them. Since the current is so sensitive to the variation in the tip-sample gap distance, atomic-scale surface corrugation can be detected by monitoring the current during the lateral scanning of the tip over the surface.

Spectroscopic measurement performed with STM, referred to as scanning tunneling spectroscopy (STS), provides information proportional to the local density of states (LDOS), the number of states per unit energy, of the sample surface. The STS measurement is usually made by positioning the STM tip over a target feature of a surface, deactivating the feedback loop to fix the STM tip height, applying a sample bias ramp, and recording tunneling current (I) or differential conductance (dI/dV).

Soft X-ray absorption fine structure (SXAFS) is based on the excitation of core-level electrons to the unoccupied states around the vacuum level, which is accompanied with soft X-ray absorption. Since each element has its own core-level energy, the SXAFS provides with element-specific information.

When the linearly polarized light is reflected from a clean surface or a surface covered by a thin film, its polarization changes and the light becomes elliptically polarized. Ellipsometry measures this change in the polarization state of light upon reflection from a surface (Azzam, Bashara in Ellipsometry and Polarized Light. North Holland, Amsterdam, 1987 [1]; Tompkins, Irene in Handbook of Ellipsometre. New York, 2005 [2]). As a result of the measurement, ellipsometric angles Ψ & Δ are obtained.

SARPES is a method in which the feature of spin resolution is added to normal ARPES measurement (see Sec. Angle-Resolved UPS). By SARPES measurement, one can obtain all the information of quantum states of electrons, i.e., energy, momentum, and spin, and thus, the measurement is sometimes called as “complete experiment.” SARPES is, therefore, one of the most powerful tools to investigate the complete electronic structure (band structure with spin resolution) of solids.

Spin-polarized scanning electron microscopy (spin SEM) is a method to visualize magnetization distribution at the surface of a ferromagnetic sample [1–4], whose principle is summarized in Fig. 102.1.Fig. 102.1Principle of spin SEM

Spin-polarized scanning tunneling microscopy (SP-STM) is a powerful tool to visualize spin-polarization vectors of sample surface atoms.

When the order of magnetic spins is locally different, it is the so-called magnetic domains. Domain structures can be randomly formed, or it can be also formed by the competition of magnetic energies such as magnetic dipole, exchange, anisotropy, and Zeeman energies.

The term “super-resolution microscopy” (SRM) includes all the optical methodologies featuring spatial resolutions exceeding the diffraction limits of optical microscopes.

The amplitude of a surface acoustic wave has the maximum value A at the surface, and it attenuates exponentially as it goes inside.

SERS is based on plasmonic enhancement of Raman scattered signals near a metal surface.

Surface magneto-optic Kerr effect (SMOKE) is based on magnetic circular dichroism (MCD), where the absorption for right and left circular polarized light is different because electronic states are split due to exchange interaction and spin–orbit coupling (Qui and Bader in Rev Sci Instrum 71:1243, 2000 [1]).

Surface Plasmon resonance (SPR) is widely utilized as a surface sensitive detection method, especially for label-free detection of biomolecules via refractive index change at metal–dielectric interface.

Surface profilometer can measure profile of surface roughness, surface texture, surface waviness, surface step height, deposited thin film thickness, and so on by means of contacting and scanning a sharp stylus with a very small measurement force less than mN.

Secondary electron (SE) emission reflects the topmost structure and chemical state of the sample surface. However, surface contaminants deposited during SEM observation hinder obtaining information of the topmost surface in a conventional SEM instrument. To obtain information of topmost surfaces, an ultrahigh vacuum environment (10−8 Pa or lower) as well a clean sample is necessary.

Surface X-ray diffraction (SXRD) is a method to observe the atomic configuration or molecular orientation at surfaces or interfaces (Robinson in Handbook on synchrotron radiation, pp 221–266, 1991; Fuoss et al. in Synchrotron radiation research: advances in surface and interface science. Plenum Press, New York, 1992; Sakata and Nakamura in Surface science techniques, pp. 165–190, 2013 [1–3]). Due to the finiteness of the material perpendicular to a surface, periodic structures at the surface in real space are Fourier-transformed to elongated rods in reciprocal lattice space.

Surface-enhanced infrared absorption (SEIRA) is an effect in which infrared absorption of molecules adsorbed on metal surfaces is significantly enhanced (10–1000 times compared to normal measurements without the metal) and has characteristic features as follows:(Osawa in Dynamic processes in electrochemical reactions studied by surface-enhanced infrared absorption spectroscopy (SEIRAS). Bull Chem Soc Jpn 70:2861–2880, 1997 [1]).

Making use of synchrotron radiation (SR) as a source of photoelectron spectroscopy (PES) has number of advantages compared to using ordinary laboratory light sources like laser, UV discharge lamps, and X-ray tubes. The light sources of most PES stations in modern synchrotron facilities are undulators followed by monochromators, both of which are designed for required photon energy ranges.

Scanning tunneling microscopy (STM) can achieve an atomic resolution easily and is nowadays a quite popular tool to reveal atomically resolved surface topography. Since, however, STM basically probes electronic states near the Fermi energy, which often contribute to the bonding with the neighboring atoms and thus are strongly affected by chemical environments, it is quite difficult to obtain chemical information.

TDS is a method for the study of adsorption, desorption, and reaction of adsorbed atoms or molecules on surfaces by measuring the desorption rate of desorbing gas from surfaces as a function of sample temperature. The basic concept of this method is that adsorbates with a higher desorption barrier desorb at higher temperature.

Time-of-flight secondary ion mass spectrometry (TOF-SIMS) is one of the most powerful surface analysis methods in terms of high sensitivity, high spatial resolution imaging, and detailed chemical information.

Events of matters in nature change with time, and it has been highly demanded to trace temporal variation of geometric and electronic structures of a sample in real time.

Time-resolved photoemission electron microscopy (TR-PEEM) has been developed based on techniques of time-resolved two-photon photoemission spectroscopy (TR-2PP).

Since the invention of scanning tunneling microscopy (STM) in 1982, the addition of high time resolution to STM has been the most challenging issue, and various time-resolved STM (TR-STM) methods have been considered and developed (Terada et al. in J Phys Condens Matter 22:264008–264015, 2010, Loth et al. in Science 329:1628–1630, 2010 [1, 2]).

TERS is the combination of scanning probe microscope (SPM) and optical spectroscopy in which the spatial resolution is as high as the one attainable by SPM while the chemical sensitivity is as high as the one in optical spectroscopy.

Monochromatic or non-monochromatic X-rays from an X-ray tube or a synchrotron radiation beamline impinge on a flat surface at a glancing angle less than the critical angle of X-ray total reflection (usually around 0.1°), and the incident X-rays are totally reflected by the flat surface. The electric field of the incident X-rays exists at the surface from the top layer to a few nanometer depth. This electric field is called an evanescent wave. This electric field of X-rays ionizes an inner-shell electron, and consequently, X-ray fluorescence is emitted. The X-ray fluorescence (XRF) is a term refers to the characteristic X-ray emission due to X-ray excitation.

According to the de Broglie’s theory, electron (with mass m and velocity v) has a wave nature with wavelength λ = h/mv (h: Planck constant), which is 0.0037 nm, if accelerated at 100 kV, and is quite small compared with λ of visible light (= 500 nm) or even X-ray (= 0.1 nm). This indicates that electron can be a source of diffraction experiments with smaller λ. Nowadays, reflection type of diffraction as illustrated in red ray-diagram of Fig. 123.1a is mostly used for surface analysis using low-energy beam (LEED), while the transmission electron diffraction (TED), as illustrated by green ray-diagram in Fig. 123.1a, is applied mainly for inner structure of thin crystals by using TEM (transmission electron microscope) with relatively higher energy.Fig. 123.1a Ray diagrams for both “transmission” and “reflection” type of electron diffraction modes are illustrated with green and red arrows, respectively. b Principle of diffraction condition in transmission case is shown schematically

TEM is an observation technique in which a high coherent electron wave (a plane wave) illuminates a thin specimen, and a transmitted electron wave is collected by magnetic lenses to make high-resolution images and transmission electron diffraction patterns. A basic principle for TEM is very similar to that for an optical microscope, and thus, it can be noticed that a light wave in the optical microscope is replaced with an electron wave in TEM.

UPS is a photoelectron spectroscopy technique using photons in the ultraviolet region (typically from 10 to 150 eV) as an excitation source. The technique is used to study valence electronic structures of solid surfaces, molecular orbital energies of adsorbed species and work functions of the surfaces and their changes induced by the adsorption of atoms and molecules. Shallow (low binding energy) core levels of composite atoms of the surfaces are also accessible by UPS so that the chemical state analysis is possible like X-ray photoelectron spectroscopy (XPS).

UV–Vis spectrophotometry is routinely used in the quantitative chemical analysis of solutions. In this article, applications to solid-state spectroscopy are described. This method detects optical transmittance/reflectance, i.e., intensity ratios of the transmitted/reflected light from a sample to the incident monochromatic light in the visible and adjacent (near-, mid-UV, and near-infrared) ranges, viz., 190–2500 nm (0.5–6.5 eV). The spectra are usually detected by scanning the monochromator (Fig. 126.1) and provide information about electronic excitation states in solids/molecules.

Sum frequency generation (SFG) is one of the second-order nonlinear optical processes in which two incident photons are up-converted to one photon having the energy (frequency) of the sum of these two inputs (Shen in The Principles of Nonlinear Optics. John Wiley & Sons, Inc, 1984[1]). Because this optical process is forbidden in the region having inversion symmetry under the dipole approximation, the SFG signal is not generated in the bulk media but arises only from the interface region. Therefore, SFG provides interface-selective information.

X-ray absorption near edge structure (XANES) is a part of X-ray absorption spectroscopy methods to observe electronic structures of elements of interest. XANES spectra contain information typically on electronic structures, chemical states, and local symmetries with element specificity (Bunker in Introduction to XAFS: A Practical Guide to X-ray Absorption Fine Structure Spectroscopy. Cambridge University Press, 2010[1]).

X-ray-aided noncontact atomic force microscopy (XANAM) is a spectroscopic and imaging technique in the combination of noncontact atomic force microscopy (NC-AFM) and synchrotron radiation (SR) X-ray, providing chemical imaging of sample surface beneath the AFM tip (Suzuki in J Phys: Conf Ser 61:1117–1121, 2007; Suzuki in Bull. Chem Soc Jpn 88:240–250, 2015[1]).

X-ray CTR scattering is a rod-shaped X-ray scattering appearing in the direction perpendicular to a crystalline surface (Fig. 130.1a) (Feidenhans’l in Surf Sci Rep 10:105–188, 1989[1]). Sharp truncation of the electron density of crystalline materials at the surface results in the CTRs.

XMCD is the difference in the X-ray absorption intensities between the right- and left-hand circular polarizations.

When an X-ray is irradiated to a solid sample, electrons are emitted by photoelectric and Auger effects.

X-ray reflectivity (XRR) is widely used for observing the structure of surfaces, thin films, and multilayers on the scale of nanometers.

Under the Bragg condition of X-rays in a crystal, the interference of incident and diffracted beams produces X-ray standing wave (XSW) field.

In Chapter “Challenges of Real-Scale Production with Smart Dynamic Casting”, low-resolution Figure 4 is replaced with high resolution, Figure 5 is replaced with new figure and Figure 6 and the graph near are positioned as per the standard.