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X-ray Absorption Spectroscopy (XAS) is a synchrotron-based analytical technique used to investigate the electronic and local atomic structures of materials with element-specific precision. By measuring the absorption of X-rays as a function of photon energy across the absorption edge of a target element, XAS provides two key types of structural information:

• X-ray Absorption Near Edge Structure (XANES) – which reveals oxidation states, chemical environments, and electronic configurations; and
• Extended X-ray Absorption Fine Structure (EXAFS) – which identifies coordination numbers, interatomic distances, and the geometric arrangement surrounding the absorbing atom.

Time resolved X-ray Absorption Spectroscopy (TRXAS) measures the X-ray absorption coefficient at specific energy levels over extremely short time intervals. Capturing spectra in the pico- to millisecond range, it allows researchers to track the evolution of local electronic and geometric structures. It is essential for observing transient intermediate states in rapid chemical reactions.

Micro-XAS: This method utilizes sophisticated X-ray optics to focus the beam down to a micrometer scale. It performs X-ray Absorption Spectroscopy on tiny, specific spots within a heterogeneous sample to determine local oxidation states and coordination chemistry. This provides high spatial resolution for complex materials.

GIXAS: X-rays are directed at the sample at a very shallow, “grazing” angle near the critical angle for total reflection. This geometry limits the penetration depth of the X-rays, making the technique exceptionally sensitive to the surface and thin-film layers. It minimizes background noise from the bulk substrate.

X-ray Fluorescence (XRF) is based on the interaction between high-energy X-rays and the atoms in a sample. When the sample is irradiated with primary X-rays, inner-shell electrons are ejected, creating vacancies. Electrons from higher energy levels then fill these vacancies, releasing secondary X-rays (fluorescent X-rays) with energies characteristic of each element. By detecting and analyzing these emitted X-rays, XRF provides qualitative and quantitative elemental composition without destroying the sample.

TXRF is based on the excitation of atoms by an incident X-ray beam under total reflection conditions at very small angles. This geometry minimizes background scattering and enhances the detection of fluorescence signals from trace elements. The emitted characteristic X-rays are analyzed to determine elemental composition. Because the penetration depth is extremely shallow, the technique is highly surface-sensitive.

Synchrotron-based Fourier transform infrared (SR-mFTIR) microspectroscopy redefines the limits of chemical mapping by coupling the analytical power of infrared spectroscopy with the extreme brilliance of synchrotron light. Unlike conventional thermal sources, synchrotron radiation provides a highly collimated photon beam effectively 1,000 times brighter than a standard instrument.

This capability allows researchers to focus light onto microscopic samples with diffraction-limited spatial resolution while maintaining an exceptional Signal-to-Noise Ratio (SNR). The result is high-definition chemical mapping at the micrometer scale, revealing fundamental vibrational transitions and molecular fingerprints with unparalleled clarity.

Photoelectron Emission Spectroscopy is based on the photoelectric effect, where incident photons with sufficient energy strike a material and cause the emission of electrons from its surface. The kinetic energy of these emitted electrons is measured to determine their binding energy within the material. This information provides insight into the electronic structure and chemical composition of the sample. PES is widely used to analyze surface chemistry and electronic states of atoms and molecules.

XPS: This is a specific form of PES that uses X-rays to eject core-level electrons from atoms within the top 1-10 nm of a surface. The energy of the ejected electrons is unique to each element and its chemical environment. This allows for precise identification of elemental composition and oxidation states.

ARXPS: By varying the emission angle at which photoelectrons are detected, this technique changes the effective depth being probed. Steeper angles provide information from deeper layers, while shallow angles focus on the extreme surface. It enables non-destructive depth profiling of ultra-thin films.

UPS: This technique utilizes ultraviolet light to eject electrons specifically from the valence bands and molecular orbitals. Because UV photons have lower energy than X-rays, the kinetic energy of the ejected electrons provides detailed information about the highest occupied electronic states. It is primarily for measuring work functions and band alignments.

ARPES: It measures both the kinetic energy and the emission angle (momentum) of photoelectrons ejected from a crystalline sample. Applying conservation laws directly maps the electronic band structure in momentum space. It is the most powerful tool for studying the electronic properties of quantum materials.

ARXAS: This technique measures X-ray absorption while changing the angle between the X-ray polarization vector and the sample’s orientation. Because X-ray absorption is highly directional, it reveals the preferential orientation of specific bonds. It is commonly used to study ordered molecular films and anisotropic crystals.

NEXAFS: It involves measuring the X-ray absorption spectrum in the region near the absorption edge, typically within 50 eV of the threshold. This region is sensitive to the transition of core electrons to unoccupied molecular orbitals. It provides detailed information on local bonding environments and molecular orientations.

Micro-XPS: A focused X-ray beam is used to perform photoelectron spectroscopy on a micrometer-scale spot. By raster-scanning the beam, the technique can map the chemical states of different elements across a surface. It is critical for analyzing the heterogeneity of microelectronic components and materials.

Micro-ARPES: This technique combines the momentum-resolved capabilities of ARPES with a micro-focused photon beam. It allows researchers to perform band structure mapping on micrometer-sized samples or specific domains. This is particularly useful for studying small flakes of 2D materials or heterogeneous surfaces.

Micro EELS: It measures the energy lost by an electron beam as it interacts with a sample, typically over a microscopic or nanoscopic area. The energy loss corresponds to electronic excitations, plasmons, or core-level transitions. It provides localized chemical and electronic information similar to XAS but with higher spatial resolution.

Micro-NEXAFS: A focused X-ray beam is used to probe near-edge absorption features at the micrometer scale. By scanning the beam across the sample, the technique maps the electronic structure and chemical bonding of specific elements in heterogeneous materials. It is essential for studying chemical variations at small spatial scales.

Auger yield Micro NEXAFS: A focused X-ray beam is used to excite electrons, and Auger electron emission is detected to obtain near-edge absorption information. The technique provides surface-sensitive chemical analysis by collecting signals from the top few nanometers of the material. It is highly effective for investigating surface and interface properties.

Powder X-ray Diffraction (PXRD) is based on the diffraction of X-rays by the crystalline planes of a powdered sample. When X-rays interact with the sample, they are scattered at specific angles according to Bragg’s law, generating a characteristic diffraction pattern. This pattern reflects the crystal structure, phase composition, and lattice parameters of the material. By analyzing the positions and intensities of the diffraction peaks, detailed structural information can be obtained.

Anomalous X-ray Diffraction (AXRD) utilizes the variation in atomic scattering factors near the absorption edge of specific elements. By tuning the X-ray energy close to the absorption edge, the scattering contribution of selected elements changes significantly. This enables element-specific structural analysis and enhances contrast between different atomic species. AXRD is particularly useful for distinguishing similar elements and investigating site occupancy and local structural environments.

Macromolecular Crystallography (MX) technique enables the determination of the atomic structures of biomolecules. When a crystal containing macromolecules is hit by X-rays, the X-rays diffract in many directions, thus creating a unique diffraction recorded on a detector. The resulting X-ray data are mathematically processed to reconstruct an electron density map, thus revealing the precise 3D arrangement of atoms. This is essential for gaining biological insights and understanding the function of complex molecules.

Residue Stress (Sin²Ψ method): This technique measures the change in the distance between atomic planes (d-spacing) as the sample is tilted at various angles (ψ). These shifts in the diffraction peaks indicate lattice strain caused by internal stresses. It provides a non-destructive way to calculate the residual stress within a material.

Low-Energy Electron Diffraction (LEED) uses low-energy electrons (typically 20–200 eV) incident on a crystalline surface to produce diffraction patterns. The diffracted electrons form characteristic spots that reflect the surface atomic arrangement. This allows determination of surface symmetry, periodicity, and reconstruction.

Micro-LEED: It uses a focused beam of low-energy electrons to produce a diffraction pattern from the topmost atomic layers of a surface. The micro-focus allows for the investigation of crystalline symmetry in small domains or individual grains. It is essential for verifying the quality of surface reconstructions.

LEED‑IV extends conventional LEED by measuring the intensity of diffracted electron beams as a function of incident electron energy (I–V curves). These energy-dependent intensity variations arise from multiple scattering interactions within the surface atomic layers. By comparing experimental I–V curves with theoretical simulations, precise atomic positions and surface relaxations can be determined. This approach provides quantitative structural information beyond symmetry analysis.

Small-Angle X-ray Scattering (SAXS) is a technique that measures X-rays scattered at very small angles to investigate structures at larger length scales (typically 1–100 nm). It provides information about the size, shape, and distribution of nanoscale structures such as particles, pores, and macromolecules.

Wide-Angle X-ray Scattering (WAXS) measures X-rays scattered at large angles, corresponding to atomic-scale distances (0.1–1 nm). This technique reveals the degree of crystallinity, crystal size, and lattice parameters, and is widely applied in the study of polymers, nanocomposites, and other crystalline materials.

GIWAXS: This technique combines the surface sensitivity of grazing incidence geometry with wide-angle scattering. By keeping the incident angle very low, the scattering signal comes predominantly from the thin-film surface rather than the substrate. It is ideal for studying the molecular packing and orientation in organic electronics.

XRR: X-rays are directed at a flat sample at very small grazing angles, and the reflected intensity is measured. The resulting interference patterns (Kiessig fringes) depend on the thickness, density, and roughness of the layers. It is a standard tool for characterizing thin films and multi-layer stacks.

PEEM is based on the emission of electrons from a material’s surface when illuminated by ultraviolet or synchrotron radiation. The emitted photoelectrons are collected and magnified through an electron optics system to produce high-resolution surface images. The contrast arises from variations in work function, composition, and electronic structure.

LEEM: Low-energy electrons are reflected off a surface and imaged through an electron microscope lens system. It provides real-time, high-surface-sensitivity images of topography and surface structures. It is often used to watch dynamic processes like crystal growth or phase transitions as they happen.

Low-Energy Electron Microscopy with Intensity–Voltage (LEEM‑IV) analysis measures the variation of reflected electron intensity as a function of incident electron energy. By scanning electron energies typically in the 0–30 eV range, the technique provides insight into surface electronic structure, thickness, and atomic layer interference effects. The oscillatory behavior in IV curves arises from quantum interference of electron waves within thin films. This enables precise, real-time characterization of surface morphology and layered materials at the nanoscale.

Micro-XRF operates by irradiating a sample with a focused beam of X-rays, causing inner-shell ionization of atoms. As electrons from higher energy levels fill the vacancies, characteristic fluorescent X-rays are emitted. These emitted X-rays have element-specific energies, allowing qualitative and quantitative identification of elements. By scanning the beam across the sample, spatially resolved elemental maps can be generated.

XFI is an analytical technique that uses X-ray excitation to map the spatial distribution of elements within a sample. When a sample is irradiated by an X-ray beam, atoms in the sample emit characteristic fluorescence X-rays. These emitted X-rays are detected and analyzed to determine the elemental composition at different positions, creating an image that shows how elements are distributed across the sample.

Two main approaches:

• Micro-beam XFI (mXI) – Uses a focused X-ray beam and scans the sample pixel by pixel.
• Full-field XFI (FXI) – Uses a large, unfocused X-ray beam and a position-sensitive detector (e.g., pnCCD), capturing the entire field simultaneously.

Synchrotron Radiation X-ray Tomographic Microscopy (SRXTM) is an advanced imaging technique that enables non-destructive, three-dimensional visualization of internal structures within a sample. It works by acquiring multiple X-ray projections at different angles and reconstructing them into cross-sectional slices, forming a detailed 3D image.

X-ray 2D Imaging: This is a high-resolution transmission technique where X-rays pass through a sample to create a projection image on a detector. Due to the high flux of synchrotron light, these images can be captured very quickly and with high contrast. It is used for real-time monitoring of internal structural changes.

Imaging NEXAFS: This technique generates a spatial map of the absorption characteristics near the X-ray edge. By imaging at specific photon energies, it can distinguish between different chemical bonds or molecular orientations across a sample. It is a key tool for studying organic thin films and biological samples.

Imaging X-ray Photoelectron Spectroscopy is based on the photoelectric effect, where X-rays irradiate a sample and induce the emission of core-level electrons. The kinetic energy of these electrons is analyzed to determine their binding energies, providing information about elemental composition and chemical states. By combining this measurement with spatially resolved detection, Imaging XPS generates detailed chemical maps of the sample surface. This technique enables visualization of the distribution of elements and compounds with high surface sensitivity.

Work Function Mapping measures the spatial variation of the work function across a material surface by analyzing the energy distribution of emitted or reflected electrons. The work function reflects the local electronic properties and surface potential. This technique provides high-resolution mapping of surface inhomogeneities at the microscale.

Deep X-ray Lithography (DXL) uses high-energy synchrotron X-rays to create precise microstructures in thick photoresist materials. Its deep penetration enables high aspect ratio structures with smooth vertical sidewalls, forming the foundation of LIGA-based fabrication. The MES Laboratory and Beamline 6 provide advanced facilities supporting microfabrication technologies such as photolithography, thin-film deposition, and etching for various high-tech applications.