Advanced UV and X-ray Probes

Capabilities / Major Equipment

Small-angle and Wide-angle X-ray Scattering for structural probing on length scales from less than 1 nm to ~ 300 nm in crystals, powders, solutions and soft materials in a controlled environment. The set-up is capable of resonant scattering (7 keV to 20 keV), grazing-incidence measurements (GISAXS and GIXD) on thin films; simultaneous SAXS/WAXS; microbeam SAXS (down to 20 microns); and time-resolved SAXS at up to 30 frames per second, with sample-detector distances of up to 5 m.

Low Energy Electron Microscopy and X-ray Photo-Emission Electron Microscopy
The sample is illuminated by either an electron beam or focused monochromatic soft X-ray radiation with tunable photon energy (15-180eV) and a vertical beam with a 30-50 mm size. Modes of operation include mirror electron microscopy (MEM), bright-field and dark-field LEEM, selected area low-energy electron diffraction (m-LEED), selected-area angle-resolved photoelectron spectroscopy (m-ARPES), X-ray photoelectron spectroscopy (XPS), NSLS ENDSTATIONs and XPEEM. The spatial resolution in the LEEM mode is better than 10 nm, and approximately 50 nm in the XPEEM mode, with an energy resolution of about 0.3 eV. The m-ARPES and m-LEED measurements can be done in an area as small as 2mm. The sample holder allows heating by electron bombardment or cooling with LN2, covering a sample temperature range from 200K to 1800K.

Ambient Pressure X-ray Photoelectron Spectroscopy using an end-station that focuses on surface chemical analysis via core-level photoelectron spectroscopy at gas pressures up to ~ 1 torr and sample temperatures up to 500 °C. The photon energy range of the beamline (~ 200 eV to 800 eV) covers the O 1s, N 1s, C 1s, core levels as well as many transition metal core-levels. Three differential pumping stages allow for gas pressures in the Torr range at the sample while maintaining ultra-high vacuum conditions in the analyzer. Possible sample types include single crystals, foils, powders and some liquids.

Endstation Details

CFN SAXS/GISAXS  Endstation at NSLS

Contact: Kevin Yager

The X9 undulator beamline is a joint venture between the NSLS and the CFN. The endstation is a cutting-edge x-ray scattering instrument, which can probe material structure at the molecular- and nano-scale. Specifically, X9 is capable of performing simultaneous small-angle (SAXS) and wide-angle (WAXS) x-ray scattering measurements, including reflection-mode analysis (GISAXS and GIXD). This wide q-range enables simultaneous quantification of the size, order, and orientation of molecular/crystal packing, and nanostructure. It can study crystals, powders, solutions, and soft materials; with control of sample environment (air, vacuum, liquid, etc.) and temperature. The instrument allows for probing of surfaces, thin films and buried interfaces.

The x-ray energy can be tuned from ~8 to ~18 keV, providing access to a wide range of wave vectors, and thus size-scales, as well as supporting resonant scattering at edges of particular interest to hybrid materials.

The instrument can measure from a q of 0.002 A^-1 (structures as large as 300 nm) to a q of 4 A^-1 (structures as small as 1.6 Angstroms). The instrument provides microbeam SAXS capabilities (beam focus as small as 20 microns) for study of small sample, inside capillaries or microfluidics, or even inside individual micro-droplets. The undulator source provides high flux, enabling experiments that would take days on a lab x-ray instrument to be performed in seconds.

The X9 instrument is currently being actively used to study a variety of materials and challenging scientific problems. The instrument is in heavy demand for x-ray scattering from solutions of proteins and other biomolecules, as well as for characterization of supramolecular structures and nanoparticle lattices in solution. The reflection-mode capabilities are ideal for study of nanostructured thin films, including block-copolymers and lithographic patterns. Hybrid and hierarchical materials can also be studied in detail. For instance, the structure and crystalline orientation of heterogeneous materials used for organic solar-cells can be studied using X9, including probing the effect confining patterns and thermal history in-situ.

CFN LEEM-PEEM Endstation at NSLS

Contact: Peter Sutter

The undulator beamline U5UA hosts a commercial low-energy electron microscope (LEEM III, manufactured by Elmitec) equipped with an electron energy analyzer so that it can also be used as a photoemission electron microscope (PEEM) operating in ultra-high vacuum (UHV). The sample is illuminated either by an electron beam or by monochromatic focused soft x-ray radiation with tunable photon energy (15-150 eV) and a vertical beam size of 30-50 microns. Modes of operation include mirror electron microscopy (MEM), bright-field and dark-field low-energy electron microscopy (LEEM), low-energy electron diffraction (LEED), x-ray photoelectron spectroscopy (XPS), and x-ray photoelectron emission microscopy (XPEEM). In XPEEM pilot experiments, a lateral resolution better than 80 nm with a photoelectron energy resolution of about 0.3 eV has been achieved. For LEEM (lateral resolution 10-20 nm) and LEED, samples must be crystalline (single-crystals are preferred) and conducting (metal or semiconductor). The sample holder allows heating by electron bombardment or can be cooled by LN2, enabling sample temperatures between 200 K and about 1800 K. Current research topics include epitaxial growth of metal and semiconductor nanostructures, and surface chemistry/catalysis on metals and metal oxides under UHV conditions. For in-situ MBE growth experiments in the microscope chamber, up to two evaporators (2.75” outer flange diameter, Omicron style) as provided by the user may be installed.