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A new diffraction beamline for materials science has been built at the Canadian Light Source synchrotron. The X-ray source is an in-vacuum wiggler with a 2.5 T peak magnetic field at 5.2 mm gap. The optical configuration includes a toroidal mirror, a single side-bounce Bragg monochromator, and a cylindrical mirror, producing a sub-150 µm vertical × 500 µm horizontal focused beam with a photon energy range of 7–22 keV and a flux of 1012 photons per second at the sample position. Three endstations are currently open to general users, and the techniques available include high-resolution powder diffraction, small molecule crystallography, X-ray reflectivity, in situ rapid thermal annealing, and SAXS/WAXS. The beamline design parameters, calculated and measured performance, and initial experimental results are presented to demonstrate the capabilities for materials science.

X-rays are used as a probe in many materials analysis techniques, but they may induce changes in the sample that can invalidate the measurement. Strategies that overcome “radiation damage” are therefore desirable. Tuning the incident photon energy below a core electron excitation edge of a material (where only valence excitation takes place) rather than above it (where primarily core excitation occurs) has been theorized as a way to reduce radiation damage. To investigate this strategy, we used a scanning transmission X-ray microscope to expose thin films of organic polymers to X-rays with photon energies below and above the C 1s excitation edge. The extent of radiation damage was quantified by X-ray absorption spectroscopy and lithography. We found that the amount of radiation damage per unit absorbed dose was the same using incident photons below and above the C 1s excitation edge. We conclude that the turn on of Auger processes when C 1s holes are created does not affect the overall radiation damage outcome.

A cryo scanning transmission X-ray microscope, the cryo-STXM, has been designed and commissioned at the Canadian Light Source synchrotron. The instrument is designed to operate from 100 - 4000 eV (lambda = 12.4 - 0.31 nm). Users can insert a previously frozen sample, through a load lock, and rotate it plus minus 70 degrees in the beam to collect tomographic data sets. The sample can be maintained for extended periods at 92 K primarily to suppress radiation damage, and a pressure on the order of 10-9 Torr to suppress sample contamination. The achieved spatial resolution (30 nm) and spectral resolution (0.1 eV) are similar to other current soft X-ray STXMs, as demonstrated by measurements on known samples and test patterns. The data acquisition efficiency is significantly more favorable for both imaging and tomography. 2D images, 3D tomograms and 4D chemical maps of automotive hydrogen fuel cell thin sections are presented to demonstrate current performance and new capabilities, namely cryo-spectrotomography in the soft X-ray region., 56 pages

A new scanning transmission X-ray microscope (STXM) optimized for cryo-spectro-tomography with soft X-rays has been designed, built and commissioned at Canadian Light Source (CLS) beamline 10ID1 (130-2700 eV). It is controlled via a new python-based software package, pySTXM. A liquid N2 goniometer (Gatan 630, -80° to 80°), mounted on a computer controlled (x,y,Theta) tilt stage allows for spectro-tomographic measurements at cryogenic temperatures (-180°C) which reduces radiation damage. The CLS cryo-STXM is unique among the set of soft X-ray STXMs currently installed around the world. Details of the cryo-STXM design and examples of its performance will be presented.

The sensitivity of organic matter to ionizing radiation is often reported in terms of a G value, or a critical dose value. In several reports which document the radiation sensitivity of organics, the response of a material to absorbed dose is shown to display first-order kinetics (i.e. exponential decay), and subsequently both a G value and a critical dose value are derived from the data. In this report the response of a thin film of polyacrylonitrile to increasing doses of 300 eV soft X-rays was measured in the C 1s near edge X-ray absorption fine structure (NEXAFS) region using a scanning transmission X-ray microscope (STXM). The C 1s(C≡N)→π ⁎ C≡N feature displayed exponential decay. Both a G value(s) and a critical dose value are derived, and the utility of each descriptor is discussed.

Sealed nanofluidic channels with cross-sections as small as 60 nm × 60 nm were created in polymer bilayers using the focused X-rays of a scanning transmission X-ray microscope. These structures were then characterized by near-edge X-ray absorption fine structure spectromicroscopy, atomic force microscopy and scanning electron microscopy. The cross-sectional area of the nanochannels could be tuned by adjusting the area patterned in x and y and/or manipulating the bottom layer thickness. The maximum length was found to be limited by the efficiency of excavation of patterned material out of the channel, and the stability of the polymer overlayer which seals the channel. Schemes toward interfacing these nanochannels with conventional microfluidics are discussed.

The sensitivity of various polymers to radiation damage by soft X-rays has been measured previously with scanning transmission X-ray microscopes. However, the critical dose values reported by different groups for the same material differ by more than 100%. Possible sources of this variability are investigated here for poly(methyl methacrylate) (PMMA) using controlled exposure to monochromatic soft X-rays at 300 eV. Radiation sensitivity, judged by several different criteria, was evaluated as a function of dose rate, pre-exposure thermal treatments and X-ray polarization. Both the measured critical dose and the dose required to initiate negative mode (cross-linking) were observed to depend only on dose, not the other factors explored. A method of determining detector efficiency from the dose required to initiate negative mode in PMMA is outlined. This method was applied to many of the soft X-ray STXMs presently operating to derive the efficiencies of their transmitted X-ray detectors in the C 1s absorption-edge region.

A variable temperature sample holder with an operational range of 15 to 200 °C and an accuracy of ±1 °C has been fabricated for scanning transmission X-ray microscopes (STXM). Here we describe the device, and use it to image the polycrystalline morphology of solid stearic acid and palmitic acid at temperatures near their respective melting points as a means of checking for possible sample heating caused by the focused X-ray beam. The melting points observed in STXM were identical to those observed by conventional methods within measurement uncertainty, even under the most extreme, high dose rate imaging conditions investigated. The beam-induced temperature rise in the sample is inferred to be below 1 °C for dose rates of up to 2.7 GGy/s.

The zone plate focused soft X-rays of a scanning transmission X-ray microscope have been used to pattern poly(methyl methacrylate) and poly(dimethylglutarimide) films by a direct write method which is analogous to lithography with a focused electron beam. The lithographic characteristics of both polymers have been determined for 300 eV X-rays. With low doses (1 MGy), developed lines 40±5 nm wide were created in poly(methyl methacrylate). At higher doses an exposure spreading phenomenon substantially increases the lateral dimensions of the developed patterns. The spreading mechanism has been identified as the point-spread function of the zone plate lens. The performance of focused soft X-ray lithography is compared to other direct write methods. The practicality of a dedicated focused soft X-ray writer instrument is discussed.

Minimal quenching of fluorescence emission was observed when the fluorescent dye AlexaFluor 514 (AF514) was covalently bound to gold monolayer protected clusters (AuMPCs) that have negligible plasmon bands (diameters

We report the synthesis of water-soluble, nearly monodisperse glycine-cysteamine (Gly-CSA) gold monolayer protected clusters (MPCs) via base deprotection of Fmoc-Gly-CSA MPCs. The resulting Gly-CSA MPCs, which have terminal primary amine groups, are fully characterized by (1)H and (13)C NMR, UV-vis spectroscopy, and TEM, and their surface properties were probed by dynamic light scattering and acid-base titrations. The characterization methods indicate that the as-synthesized particles are nearly monodisperse with an average particle size of 1.8 +/- 0.3 nm, but are only stable to aggregation in water at pHs of 4 and below. Acid-base titrations of the Gly-CSA MPCs show that the primary ammonium groups have a pK(a) of approximately 5.5, which is several orders of magnitude lower than the pK(a2) for the ammonium group of glycine (9.6). Thus, the particles are only partially protonated at intermediate pH's, which then drives the aggregation of the nanoparticles via hydrogen-bond formation. Dynamic light scattering results confirm the pH-driven aggregation of the nanoparticles, and studies with ninhydrin confirm that the primary amine groups are reactive and have potential for further functionalization. These results show that amine-terminated MPCs can be synthesized; however, their aggregation at intermediate pH's can limit their utility as building blocks for multifunctional nanoparticle syntheses.

Ag nanoparticles with a diameter of 10 ± 5 nm were generated in the gas phase by using a sputtering/aggregation source and deposited onto NaCl prisms. Internal reflection spectroscopy was utilized ...

HighlightsX-ray lithography was performed in direct write (maskless) geometry using a STXM.Sub-25nm free form features were created in PMMA.The ultimate feature size limitations of this technique are discussed. Sub-25nm continuous, reproducible features of arbitrary geometry were created by X-ray lithography in direct write (maskless) geometry, analogous to conventional electron beam lithography. This was achieved through the use of a laser interferometer-controlled scanning transmission X-ray microscope (STXM) equipped with a zone doubled Fresnel zone plate lens, and a cold development procedure. These features are among the smallest created with photons in direct write geometry.

A new soft X-ray scanning transmission X-ray microscope (STXM) optimized for cryo spectro-tomography was designed and commissioned at the Canadian Light Source (CLS). The instrument was required to achieve ultra high vacuum and be compatible with in-situ plasma cleaning. It also required a scintillator detector, and the design of this detector had to evolve to meet these environmental requirements. The scintillator deposition technique, and the suppression of background by introduction of an edge filter are also presented.

Sealed nanofluidic channels with cross sections of sub-100 nm * 100 nm were created in a polymer bilayer using the focused soft X-rays of a scanning transmission X-ray microscope and the direct write method. The width of the nanochannels can be controlled by the area patterned in X and Y, while the height can be controlled by tuning the layer thicknesses. Formation of the desired structures has been confirmed by near edge X-ray absorption fine structure spectromicroscopy and scanning electron microscopy. The maximum length of the nanochannels fabricated by this method was found to be limited by the efficiency of excavation of patterned material out of the channel, as well as the stability of the polymer over-layer which seals it. Schemes toward interfacing these nanochannels with conventional microfluidics are discussed.

The monochromatic zone plate focused soft X-rays of scanning transmission X-ray microscopes (STXM) can be used to directly write patterns in common photoresists, analogous to lithography with a focused electron or ion beam. A radiation damage spreading phenomenon when patterning with high doses was recently determined to be due to the point spread function of the optical system (Leontowich et al., Applied Physics A: Materials Science and Processing 103, 1 (2011)). We have used this phenomenon to measure the point spread function of three different STXMs by making a series of single pixel exposures in a photoresist at focus over a controlled dose range. Our results suggest this measurement is sensitive to zone plate aberrations; thus, it could be valuable feedback for optimizing zone plate fabrication schemes and STXM performance.

The stability of short period Sc/Cr and Sc/B4C/Cr multilayers was investigated over a large temperature range. The aim was to find a stable reflective coating for an off-axis parabola for focusing x rays from a soft x-ray free-electron laser. Normal incidence reflectivity, surface roughness, and intrinsic stress were investigated as a function of annealing temperature and two samples were also studied with a high-resolution transmission electron microscope (TEM), a scanning TEM, and through electron energy loss spectroscopy (EELS). Interface-engineered Sc/B4C/Cr multilayers showed increased thermal stability and higher reflectivity as compared to pure Sc/Cr multilayers.

Deposition of a carbonaceous contaminant layer on surfaces exposed to radiation exceeding 7–10 eV is ubiquitous in many fields of research. The mechanism of this deposition process is still debated. A scanning transmission x-ray microscope has been used to create and interrogate carbonaceous deposits with photon energies spanning the C 1s ionization edge. For equal fluence, the rate of carbon deposition is proportional to the x-ray absorption spectrum of the deposited material. The results are consistent with a deposition mechanism involving secondary electrons. Implications of this measurement with regard to future generations of high volume photolithography are discussed.