Bio

Paul H. Fuoss is Head of Experimental Design for the Linac Coherent Light Source where he focuses on the development of new x-ray instrumentation and techniques that exploit the capabilities of the world's first hard x-ray free electron laser.

As a graduate student at Stanford, Fuoss did his research at SLAC, using X-rays from what later became the Stanford Synchrotron Radiation Lightsource (SSRL) to investigate chalcogenide glasses. During that research, he created and developed "differential anomalous scattering" to solve important problems that required detailed understanding of the local atomic structure in liquids and glasses. The experimental and analysis approach he developed is still in wide use.

Moving on to a post-doc at Bell Labs, Fuoss worked with Peter Eisenberger and Bill Marra to create techniques to bring the power and simplicity of x-ray scattering to the study of surface structures. As a young scientist at Bell in the 1980’s, he collaborated with Ian Robinson to design and build beamline X16A at the National Synchrotron Light Source. The X16A ultra-high vacuum (UHV) diffractometer, the first in the world, was used to determine surface structures with unprecedented clarity. Fuoss explored such varied topics as fundamental aspects of melting, the nature of the technologically important Si-SiO2 interface, and optical phase-change materials.

In the course of this work, Fuoss realized that these x-ray techniques offered the opportunity for real-time studies of important materials science processes at near-atmospheric pressure and above. Partnering with David Kisker, a crystal grower at Bell Labs, and Sean Brennan at SSRL, he built a chemical vapor deposition (CVD) system adapted for real-time x-ray measurements. Installed on the PEP storage ring undulator line 5B, this system produced spectacular results revealing atomically sharp surfaces despite the complex CVD chemical environment. After the PEP program was cut short by the Loma Prieta earthquake, the team moved the system to SSRL and performed a series of experiments revealing mechanisms of CVD crystal growth that were both unexpected and which confirmed a solid connection with classic crystal growth literature.

Amid the rapid development of information technology in the late 90's, Fuoss took a six-year detour into AT&T Laboratories. Exploring approaches to merge AT&T's existing telephone network with rapidly emerging internet and cellular capabilities, he developed several novel services and led the effort to move them from Research into the business units. That experience, focused on making complex systems user friendly, has proven very useful as x-ray experiments become increasingly complicated.

In 2002, Fuoss moved to the Materials Science Division at Argonne and renewed his research in x-ray science. His work at Argonne focused on exploring time-dependent processes in crystal growth, ferroelectric materials, and ionic conduction in materials for energy applications. His work integrated advances in detectors, optics, and high brightness x-ray sources to study the evolution of materials on time scales ranging from femtoseconds to hours.

After fifteen years of research using both the Advanced Photon Source and LCLS, Fuoss moved to SLAC in 2017 to focus on the development of robust experimental facilities that exploit development of the scientific opportunities enabled by the next generation LCLS-II.

Througout his career, Fuoss has been active as a leader in the broader x-ray science community. Among other things, he has been Chair of the SSRL Users Organization, Chair of the APS Users Organization Steering Committee, and Chair of the LCLS-II Facility Advisory Committee. His contributions have been recognized at Argonne with The University of Chicago Medal for Distinguished Performance at Argonne National Laboratory in 2013, and at SLAC with the Farrel W. Lytle Award in 2015.

Current Role at Stanford

Head of Experimental Design, LCLS

Honors & Awards

  • Farrel W. Lytle Award, SSRL, SLAC National Accelerator Laboratory (2015)
  • Distinguished Performance Award At Argonne National Laboratory, The University of Chicago (2013)
  • Fellow, American Physical Society (1999)
  • NSF Post-Doctoral Fellowship (declined), National Science Foundation (1980)
  • IBM Pre-Doctoral Fellow (at Stanford University), IBM (1976-1977)
  • University Honors Fellowship, Stanford University (1975-1976)

Education & Certifications

  • PhD, Stanford University, Materials Science and Engineering (1980)
  • M.S., Stanford University, Materials Science and Engineering (1976)
  • B.S., South Dakota School of Mines and Technology, Physics (1975)

Patents

  • Paul Fuoss, Stephan Hruszkewycz, Ashish Tripathi, Andrew Ulvestad, Stefan Wild. "United States Patent 10078305 Method for phase retrieval to reduce a sampling requirement when imaging a dynamic process", UChicago Argonne, LLC, Apr 19, 2018
  • Paul Fuoss. "United States Patent 8220766 Table Guard Assembly", Jul 17, 2012
  • Paul Fuoss, Howard Katseff, Bethany Robinson. "United States Patent 7894836 Method and System for Handwritten Electronic Messaging", AT&T, Feb 22, 2011
  • Paul Fuoss, Howard Katseff, Bethany Robinson. "United States Patent 7224,991 Method and System for Handwritten Electronic Messaging", AT&T, May 29, 2007
  • Paul Fuoss, Howard Katseff, Bethany Robinson. "United States Patent 7120241 Method and Apparatus for Controlling a Network Device", AT&T, Oct 10, 2006
  • Paul Fuoss, Howard Katseff, Bethany Robinson. "United States Patent 7003308 Method and System for Handwritten Electronic Messaging", AT&T, Feb 21, 2006
  • Paul Fuoss, Howard Katseff, Bethany Robinson. "United States Patent 6970696 Method and Apparatus for Controlling a Network Device", AT&T, Nov 29, 2005

Contact

  • Work
    fuoss@SLAC.Stanford.EDU
    University - Staff Department: SLAC National Accelerator Laboratory Position: Distinguished Staff Scientist
    • 2575 Sand Hill Rd
    • Mailstop 0019
    • Menlo Park,  California  94025 

Additional Info

Links

All Publications

  • A multi-scale cognitive interaction model of instrument operations at the Linac Coherent Light Source. The Review of scientific instruments Segal, J. I., Hu, W. L., Fuoss, P. H., Ritter, F. E., Shrager, J. 2025; 96 (1)

    Abstract

    The Linac Coherent Light Source (LCLS) is the world's first x-ray free electron laser. It is a scientific user facility operated by the SLAC National Accelerator Laboratory, at Stanford, for the U.S. Department of Energy. As beam time at LCLS is extremely valuable and limited, experimental efficiency-getting the most high quality data in the least time-is critical. Our overall project employs cognitive engineering methodologies with the goal of improving experimental efficiency and increasing scientific productivity at LCLS by refining experimental interfaces and workflows, simplifying tasks, reducing errors, and improving operator safety and stress. Here, we describe a multi-agent, multi-scale computational cognitive interaction model of instrument operations at LCLS. Our model simulates the aspects of human cognition at multiple cognitive and temporal scales, ranging from seconds to hours, and among agents playing multiple roles, including instrument operator, real time data analyst, and experiment manager. The model can roughly predict impacts stemming from proposed changes to operational interfaces and workflows. Example results demonstrate the model's potential in guiding modifications to improve operational efficiency. We discuss the implications of our effort for cognitive engineering in complex experimental settings and outline future directions for research. The model is open source, and the videos of the supplementary material provide extensive detail.

    View details for DOI 10.1063/5.0239302

    View details for PubMedID 39878576

  • Structural changes across thermodynamic maxima in supercooled liquid tellurium: A water-like scenario. Proceedings of the National Academy of Sciences of the United States of America Sun, P., Monaco, G., Zalden, P., Sokolowski-Tinten, K., Antonowicz, J., Sobierajski, R., Kajihara, Y., Baron, A. Q., Fuoss, P., Chuang, A. C., Park, J., Almer, J., Hastings, J. B. 2022; 119 (28): e2202044119

    Abstract

    Liquid polymorphism is an intriguing phenomenon that has been found in a few single-component systems, the most famous being water. By supercooling liquid Te to more than 130 K below its melting point and performing simultaneous small-angle and wide-angle X-ray scattering measurements, we observe clear maxima in its thermodynamic response functions around 615 K, suggesting the possible existence of liquid polymorphism. A close look at the underlying structural evolution shows the development of intermediate-range order upon cooling, most strongly around the thermodynamic maxima, which we attribute to bond-orientational ordering. The striking similarities between our results and those of water, despite the lack of hydrogen-bonding and tetrahedrality in Te, indicate that water-like anomalies may be a general phenomenon among liquid systems with competing bond- and density-ordering.

    View details for DOI 10.1073/pnas.2202044119

    View details for PubMedID 35867742

  • A Contrast Calibration Protocol for X-ray Speckle Visibility Spectroscopy APPLIED SCIENCES-BASEL Sun, Y., Esposito, V., Hart, P., Hansson, C., Li, H., Nakahara, K., MacArthur, J., Nelson, S., Sato, T., Song, S., Sun, P., Fuoss, P., Sutton, M., Zhu, D. 2021; 11 (21)

    View details for DOI 10.3390/app112110041

    View details for Web of Science ID 000726897500001

  • Generation of highly mutually coherent hard-x-ray pulse pairs with an amplitude-splitting delay line PHYSICAL REVIEW RESEARCH Li, H., Sun, Y., Vila-Comamala, J., Sato, T., Song, S., Sun, P., Seaberg, M. H., Wang, N., Hastings, J. B., Dunne, M., Fuoss, P., David, C., Sutton, M., Zhu, D. 2021; 3 (4)

    View details for DOI 10.1103/PhysRevResearch.3.043050

    View details for Web of Science ID 000708677100006

  • Nonuniform Flow Dynamics Probed by Nanosecond X-Ray Speckle Visibility Spectroscopy. Physical review letters Sun, Y., Carini, G., Chollet, M., Decker, F. J., Dunne, M., Fuoss, P., Hruszkewycz, S. O., Lane, T. J., Nakahara, K., Nelson, S., Robert, A., Sato, T., Song, S., Stephenson, G. B., Sutton, M., Van Driel, T. B., Weninger, C., Zhu, D. 2021; 127 (5): 058001

    Abstract

    We report observations of nanosecond nonuniform colloidal dynamics in a free flowing liquid jet using ultrafast x-ray speckle visibility spectroscopy. Utilizing a nanosecond double-bunch mode, the Linac Coherent Light Source free electron laser produced pairs of femtosecond coherent hard x-ray pulses. By exploring anisotropy in the visibility of summed speckle patterns which relates to the correlation functions, we evaluate not only the average particle flow rate in a colloidal nanoparticle jet, but also the nonuniform flow field within. The methodology presented here establishes the foundation for the study of nano- and atomic-scale inhomogeneous fluctuations in complex matter using x-ray free electron laser sources.

    View details for DOI 10.1103/PhysRevLett.127.058001

    View details for PubMedID 34397240

  • Nonuniform Flow Dynamics Probed by Nanosecond X-Ray Speckle Visibility Spectroscopy PHYSICAL REVIEW LETTERS Sun, Y., Carini, G., Chollet, M., Decker, F., Dunne, M., Fuoss, P., Hruszkewycz, S. O., Lane, T. J., Nakahara, K., Nelson, S., Robert, A., Sato, T., Song, S., Stephenson, G., Sutton, M., Van Driel, T. B., Weninger, C., Zhu, D. 2021; 127 (5)

    View details for DOI 10.1103/PhysRevLett.127.058001

    View details for Web of Science ID 000679183300006

  • Accurate contrast determination for X-ray speckle visibility spectroscopy JOURNAL OF SYNCHROTRON RADIATION Sun, Y., Montana-Lopez, J., Fuoss, P., Sutton, M., Zhu, D. 2020; 27: 999–1007

    View details for DOI 10.1107/S1600577520006773

    View details for Web of Science ID 000546241000016

  • Accurate contrast determination for X-ray speckle visibility spectroscopy. Journal of synchrotron radiation Sun, Y., Montana-Lopez, J., Fuoss, P., Sutton, M., Zhu, D. 2020; 27 (Pt 4): 999-1007

    Abstract

    X-ray speckle visibility spectroscopy using X-ray free-electron lasers has long been proposed as a probe of fast dynamics in noncrystalline materials. In this paper, numerical modeling is presented to show how the data interpretation of visibility spectroscopy can be impacted by the nonidealities of real-life X-ray detectors. Using simulated detector data, this work provides a detailed analysis of the systematic errors of several contrast extraction algorithms in the context of low-count-rate X-ray speckle visibility spectroscopy and their origins are discussed. Here, it was found that the finite detector charge cloud and pixel size lead to an unavoidable `degeneracy' in photon position determination, and that the contrasts extracted using different algorithms can all be corrected by a simple linear model. The results suggest that experimental calibration of the correction coefficient at the count rate of interest is possible and essential. This allows computationally lightweight algorithms to be implemented for on-the-fly analysis.

    View details for DOI 10.1107/S1600577520006773

    View details for PubMedID 33566009

    View details for PubMedCentralID PMC7336177

  • Foreword to the special virtual issue on <i>X</i>-<i>ray free</i>-<i>electron lasers</i> JOURNAL OF SYNCHROTRON RADIATION Fuoss, P. H., Schlichting, I., Tschentscher, T., Yabashi, M. 2020; 27: 576

    Abstract

    A virtual special issue of Journal of Synchrotron Radiation advances in the field of X-ray free-electron lasers.

    View details for DOI 10.1107/S1600577520002799

    View details for Web of Science ID 000531472900001

    View details for PubMedID 32381755

    View details for PubMedCentralID PMC7285675

  • Realizing split-pulse x-ray photon correlation spectroscopy to measure ultrafast dynamics in complex matter PHYSICAL REVIEW RESEARCH Sun, Y., Dunne, M., Fuoss, P., Robert, A., Zhu, D., Osaka, T., Yabashi, M., Sutton, M. 2020; 2 (2)

    View details for DOI 10.1103/PhysRevResearch.2.023099

    View details for Web of Science ID 000602777500004

  • Design of an amplitude-splitting hard x-ray delay line with subnanoradian stability OPTICS LETTERS Li, H., Sun, Y., Sutton, M., Fuoss, P., Zhu, A. 2020; 45 (7): 2086–89

    Abstract

    We present the design and analysis of a hard x-ray split-delay optical arrangement that combines diffractive and crystal optics. Transmission gratings are employed to achieve the much-desired amplitude splitting and recombination of the beam. Asymmetric channel-cut crystals are utilized to tune the relative delay time. The use of a dispersion-compensation arrangement of the crystals allows the system to achieve subnanoradian pointing stability during a delay scan. It also minimizes wavefront distortion and preserves the pulse front and pulse duration. We analyze the performance of a prototype design that can cover a delay time range of 15 ps with a sub-20 fs time resolution at 10 keV. We anticipate that this system can fully satisfy the very demanding stability requirements for performing split-pulse x-ray photon correlation spectroscopy measurements for the investigation of fast atomic scale dynamics in complex disordered matter.

    View details for DOI 10.1364/OL.389977

    View details for Web of Science ID 000522794100124

    View details for PubMedID 32236074

  • Speckle correlation as a monitor of X-ray free-electron laser induced crystal lattice deformation. Journal of synchrotron radiation Plumley, R. n., Sun, Y. n., Teitelbaum, S. n., Song, S. n., Sato, T. n., Chollet, M. n., Nelson, S. n., Wang, N. n., Sun, P. n., Robert, A. n., Fuoss, P. n., Sutton, M. n., Zhu, D. n. 2020; 27 (Pt 6): 1470–76

    Abstract

    X-ray free-electron lasers (X-FELs) present new opportunities to study ultrafast lattice dynamics in complex materials. While the unprecedented source brilliance enables high fidelity measurement of structural dynamics, it also raises experimental challenges related to the understanding and control of beam-induced irreversible structural changes in samples that can ultimately impact the interpretation of experimental results. This is also important for designing reliable high performance X-ray optical components. In this work, X-FEL beam-induced lattice alterations are investigated by measuring the shot-to-shot evolution of near-Bragg coherent scattering from a single crystalline germanium sample. It is shown that X-ray photon correlation analysis of sequential speckle patterns measurements can be used to monitor the nature and extent of lattice rearrangements. Abrupt, irreversible changes are observed following intermittent high-fluence monochromatic X-ray pulses, thus revealing the existence of a threshold response to X-FEL pulse intensity.

    View details for DOI 10.1107/S1600577520011509

    View details for PubMedID 33147171

  • Double-pulse speckle contrast correlations with near Fourier transform limited free-electron laser light using hard X-ray split-and-delay. Scientific reports Roseker, W. n., Lee, S. n., Walther, M. n., Lehmkühler, F. n., Hankiewicz, B. n., Rysov, R. n., Hruszkewycz, S. O., Stephenson, G. B., Sutton, M. n., Fuoss, P. H., Sikorski, M. n., Robert, A. n., Song, S. n., Grübel, G. n. 2020; 10 (1): 5054

    Abstract

    The ability to deliver two coherent X-ray pulses with precise time-delays ranging from a few femtoseconds to nanoseconds enables critical capabilities of probing ultra-fast phenomena in condensed matter systems at X-ray free electron laser (FEL) sources. Recent progress made in the hard X-ray split-and-delay optics developments now brings a very promising prospect for resolving atomic-scale motions that were not accessible by previous time-resolved techniques. Here, we report on characterizing the spatial and temporal coherence properties of the hard X-ray FEL beam after propagating through split-and-delay optics. Speckle contrast analysis of small-angle scattering measurements from nanoparticles reveals well-preserved transverse coherence of the beam. Measuring intensity fluctuations from successive X-ray pulses also reveals that only single or double temporal modes remain in the transmitted beam, corresponding to nearly Fourier transform limited pulses.

    View details for DOI 10.1038/s41598-020-61926-y

    View details for PubMedID 32193442

  • Coherent X-ray spectroscopy reveals the persistence of island arrangements during layer-by-layer growth NATURE PHYSICS Ju, G., Xu, D., Highland, M., Thompson, C., Zhou, H., Eastman, J. A., Fuoss, P. H., Zapol, P., Kim, H., Stephenson, G. 2019; 15 (6): 589-+

    View details for DOI 10.1038/s41567-019-0448-1

    View details for Web of Science ID 000470086800023

  • Compact hard x-ray split-delay system based on variable-gap channel-cut crystals OPTICS LETTERS Sun, Y., Wang, N., Song, S., Sun, P., Chollet, M., Sato, T., van Driel, T. B., Nelson, S., Plumley, R., Montana-Lopez, J., Teitelbaum, S. W., Haber, J., Hastings, J. B., Baron, A. R., Sutton, M., Fuoss, P. H., Robert, A., Zhu, D. 2019; 44 (10): 2582–85

    Abstract

    We present the concept and a prototypical implementation of a compact x-ray split-delay system that is capable of performing continuous on-the-fly delay scans over a range of ∼10  ps with sub-100 nanoradian pointing stability. The system consists of four channel-cut silicon crystals, two of which have gradually varying gap sizes from intentional 5 deg asymmetric cuts. The delay adjustment is realized by linear motions of these two monolithic varying-gap channel cuts, where the x-ray beam experiences pairs of anti-parallel reflections, and thus becomes less sensitive in output beam pointing to motion imperfections of the translation stages. The beam splitting is accomplished by polished crystal edges. A high degree of mutual coherence between the two branches at the focus is observed by analyzing small-angle coherent x-ray scattering patterns. We envision a wide range of applications including single-shot x-ray pulse temporal diagnostics, studies of high-intensity x-ray-matter interactions, as well as measurement of dynamics in disordered material systems using split-pulse x-ray photon correlation spectroscopy.

    View details for DOI 10.1364/OL.44.002582

    View details for Web of Science ID 000467906400050

    View details for PubMedID 31090737

  • Characterization of the X-ray coherence properties of an undulator beamline at the Advanced Photon Source JOURNAL OF SYNCHROTRON RADIATION Ju, G., Highland, M. J., Thompson, C., Eastman, J. A., Fuoss, P. H., Zhou, H., Dejus, R., Stephenson, G. 2018; 25: 1036-1047

    Abstract

    In anticipation of the increased use of coherent X-ray methods and the need to upgrade beamlines to match improved source quality, here the coherence properties of the X-rays delivered by beamline 12ID-D at the Advanced Photon Source have been characterized. The measured X-ray divergence, beam size, brightness and coherent flux at energies up to 26 keV are compared with the calculated values from the undulator source, and the effects of beamline optics such as a mirror, monochromator and compound refractive lenses are evaluated. Diffraction patterns from slits as a function of slit width are analyzed using wave propagation theory to obtain the beam divergence and thus coherence length. Imaging of the source using a compound refractive lens was found to be the most accurate method for determining the vertical divergence. While the brightness and coherent flux obtained without a monochromator (`pink beam') agree well with those calculated for the source, those measured with the monochromator were a factor of three to six lower than the source, primarily because of vertical divergence introduced by the monochromator. The methods described herein should be widely applicable for measuring the X-ray coherence properties of synchrotron beamlines.

    View details for DOI 10.1107/S1600577518006501

    View details for Web of Science ID 000437744600015

    View details for PubMedID 29979165

    View details for PubMedCentralID PMC6038611

  • Towards ultrafast dynamics with split-pulse X-ray photon correlation spectroscopy at free electron laser sources NATURE COMMUNICATIONS Roseker, W., Hruszkewycz, S. O., Lehmkuehler, F., Walther, M., Schulte-Schrepping, H., Lee, S., Osaka, T., Struder, L., Hartmann, R., Sikorski, M., Song, S., Robert, A., Fuoss, P. H., Sutton, M., Stephenson, G. B., Gruebel, G. 2018; 9: 1704

    Abstract

    One of the important challenges in condensed matter science is to understand ultrafast, atomic-scale fluctuations that dictate dynamic processes in equilibrium and non-equilibrium materials. Here, we report an important step towards reaching that goal by using a state-of-the-art perfect crystal based split-and-delay system, capable of splitting individual X-ray pulses and introducing femtosecond to nanosecond time delays. We show the results of an ultrafast hard X-ray photon correlation spectroscopy experiment at LCLS where split X-ray pulses were used to measure the dynamics of gold nanoparticles suspended in hexane. We show how reliable speckle contrast values can be extracted even from very low intensity free electron laser (FEL) speckle patterns by applying maximum likelihood fitting, thus demonstrating the potential of a split-and-delay approach for dynamics measurements at FEL sources. This will enable the characterization of equilibrium and, importantly also reversible non-equilibrium processes in atomically disordered materials.

    View details for DOI 10.1038/s41467-018-04178-9

    View details for Web of Science ID 000431008800001

    View details for PubMedID 29703980

    View details for PubMedCentralID PMC5923200

  • An instrument for <i>in situ</i> coherent x-ray studies of metal-organic vapor phase epitaxy of III-nitrides REVIEW OF SCIENTIFIC INSTRUMENTS Ju, G., Highland, M. J., Yanguas-Gil, A., Thompson, C., Eastman, J. A., Zhou, H., Brennan, S. M., Stephenson, G., Fuoss, P. H. 2017; 88 (3): 035113

    Abstract

    We describe an instrument that exploits the ongoing revolution in synchrotron sources, optics, and detectors to enable in situ studies of metal-organic vapor phase epitaxy (MOVPE) growth of III-nitride materials using coherent x-ray methods. The system includes high-resolution positioning of the sample and detector including full rotations, an x-ray transparent chamber wall for incident and diffracted beam access over a wide angular range, and minimal thermal sample motion, giving the sub-micron positional stability and reproducibility needed for coherent x-ray studies. The instrument enables surface x-ray photon correlation spectroscopy, microbeam diffraction, and coherent diffraction imaging of atomic-scale surface and film structure and dynamics during growth, to provide fundamental understanding of MOVPE processes.

    View details for DOI 10.1063/1.4978656

    View details for Web of Science ID 000397871400072

    View details for PubMedID 28372371

  • High-resolution three-dimensional structural microscopy by single-angle Bragg ptychography NATURE MATERIALS Hruszkewycz, S. O., Allain, M., Holt, M. V., Murray, C. E., Holt, J. R., Fuoss, P. H., Chamard, V. 2017; 16 (2): 244-251

    Abstract

    Coherent X-ray microscopy by phase retrieval of Bragg diffraction intensities enables lattice distortions within a crystal to be imaged at nanometre-scale spatial resolutions in three dimensions. While this capability can be used to resolve structure-property relationships at the nanoscale under working conditions, strict data measurement requirements can limit the application of current approaches. Here, we introduce an efficient method of imaging three-dimensional (3D) nanoscale lattice behaviour and strain fields in crystalline materials with a methodology that we call 3D Bragg projection ptychography (3DBPP). This method enables 3D image reconstruction of a crystal volume from a series of two-dimensional X-ray Bragg coherent intensity diffraction patterns measured at a single incident beam angle. Structural information about the sample is encoded along two reciprocal-space directions normal to the Bragg diffracted exit beam, and along the third dimension in real space by the scanning beam. We present our approach with an analytical derivation, a numerical demonstration, and an experimental reconstruction of lattice distortions in a component of a nanoelectronic prototype device.

    View details for DOI 10.1038/NMAT4798

    View details for Web of Science ID 000393349800019

    View details for PubMedID 27869823

  • Three Dimensional Variable-Wavelength X-Ray Bragg Coherent Diffraction Imaging PHYSICAL REVIEW LETTERS Cha, W., Ulvestad, A., Allain, M., Chamard, V., Harder, R., Leake, S. J., Maser, J., Fuoss, P. H., Hruszkewycz, S. O. 2016; 117 (22): 225501

    Abstract

    We present and demonstrate a formalism by which three-dimensional (3D) Bragg x-ray coherent diffraction imaging (BCDI) can be implemented without moving the sample by scanning the energy of the incident x-ray beam. This capability is made possible by introducing a 3D Fourier transform that accounts for x-ray wavelength variability. We demonstrate the approach by inverting coherent Bragg diffraction patterns from a gold nanocrystal measured with an x-ray energy scan. Variable-wavelength BCDI will expand the breadth of feasible in situ 3D strain imaging experiments towards more diverse materials environments, especially where sample manipulation is difficult.

    View details for DOI 10.1103/PhysRevLett.117.225501

    View details for Web of Science ID 000388630000021

    View details for PubMedID 27925753

  • Utilizing broadband X-rays in a Bragg coherent X-ray diffraction imaging experiment JOURNAL OF SYNCHROTRON RADIATION Cha, W., Liu, W., Harder, R., Xu, R., Fuoss, P. H., Hruszkewycz, S. O. 2016; 23: 1241-1244

    Abstract

    A method is presented to simplify Bragg coherent X-ray diffraction imaging studies of complex heterogeneous crystalline materials with a two-stage screening/imaging process that utilizes polychromatic and monochromatic coherent X-rays and is compatible with in situ sample environments. Coherent white-beam diffraction is used to identify an individual crystal particle or grain that displays desired properties within a larger population. A three-dimensional reciprocal-space map suitable for diffraction imaging is then measured for the Bragg peak of interest using a monochromatic beam energy scan that requires no sample motion, thus simplifying in situ chamber design. This approach was demonstrated with Au nanoparticles and will enable, for example, individual grains in a polycrystalline material of specific orientation to be selected, then imaged in three dimensions while under load.

    View details for DOI 10.1107/S1600577516010523

    View details for Web of Science ID 000382299500027

    View details for PubMedID 27577782

  • A liquid jet setup for x-ray scattering experiments on complex liquids at free-electron laser sources REVIEW OF SCIENTIFIC INSTRUMENTS Steinke, I., Walther, M., Lehmkuehler, F., Wochner, P., Valerio, J., Mager, R., Schroer, M. A., Lee, S., Roseker, W., Jain, A., Sikorski, M., Song, S., Hartmann, R., Huth, M., Strueder, L., Sprung, M., Robert, A., Fuoss, P. H., Stephenson, G. B., Gruebel, G. 2016; 87 (6): 063905

    Abstract

    In this paper we describe a setup for x-ray scattering experiments on complex fluids using a liquid jet. The setup supports Small and Wide Angle X-ray Scattering (SAXS/WAXS) geometries. The jet is formed by a gas-dynamic virtual nozzle (GDVN) allowing for diameters ranging between 1 μm and 20 μm at a jet length of several hundred μm. To control jet properties such as jet length, diameter, or flow rate, the instrument is equipped with several diagnostic tools. Three microscopes are installed to quantify jet dimensions and stability in situ. The setup has been used at several beamlines performing both SAXS and WAXS experiments. As a typical example we show an experiment on a colloidal dispersion in a liquid jet at the X-ray Correlation Spectroscopy instrument at the Linac Coherent Light Source free-electron laser.

    View details for DOI 10.1063/1.4953921

    View details for Web of Science ID 000379177000052

    View details for PubMedID 27370468

  • Strain Imaging of Nanoscale Semiconductor Heterostructures with X-Ray Bragg Projection Ptychography PHYSICAL REVIEW LETTERS Holt, M. V., Hruszkewycz, S. O., Murray, C. E., Holt, J. R., Paskiewicz, D. M., Fuoss, P. H. 2014; 112 (16): 165502

    Abstract

    We report the imaging of nanoscale distributions of lattice strain and rotation in complementary components of lithographically engineered epitaxial thin film semiconductor heterostructures using synchrotron x-ray Bragg projection ptychography (BPP). We introduce a new analysis method that enables lattice rotation and out-of-plane strain to be determined independently from a single BPP phase reconstruction, and we apply it to two laterally adjacent, multiaxially stressed materials in a prototype channel device. These results quantitatively agree with mechanical modeling and demonstrate the ability of BPP to map out-of-plane lattice dilatation, a parameter critical to the performance of electronic materials.

    View details for DOI 10.1103/PhysRevLett.112.165502

    View details for Web of Science ID 000335325900007

    View details for PubMedID 24815657

  • Coherent Bragg nanodiffraction at the hard X-ray Nanoprobe beamline PHILOSOPHICAL TRANSACTIONS OF THE ROYAL SOCIETY A-MATHEMATICAL PHYSICAL AND ENGINEERING SCIENCES Hruszkewycz, S. O., Holt, M. V., Maser, J., Murray, C. E., Highland, M. J., Folkman, C. M., Fuoss, P. H. 2014; 372 (2010): 20130118

    Abstract

    Bragg coherent diffraction with nanofocused hard X-ray beams provides unique opportunities for quantitative in situ studies of crystalline structure in nanoscale regions of complex materials and devices by a variety of diffraction-based techniques. In the case of coherent diffraction imaging, a major experimental challenge in using nanoscale coherent beams is maintaining a constant scattering volume such that coherent fringe visibility is maximized and maintained over the course of an exposure lasting several seconds. Here, we present coherent Bragg diffraction patterns measured from different nanostructured thin films at the Sector 26 Nanoprobe beamline at the Advanced Photon Source and demonstrate that with nanoscale positional control, coherent diffraction patterns can be measured with source-limited fringe visibilities more than 50% suitable for imaging by coherent Bragg ptychography techniques.

    View details for DOI 10.1098/rsta.2013.0118

    View details for Web of Science ID 000332379600011

    View details for PubMedID 24470418

    View details for PubMedCentralID PMC3900036

  • Imaging Local Polarization in Ferroelectric Thin Films by Coherent X-Ray Bragg Projection Ptychography PHYSICAL REVIEW LETTERS Hruszkewycz, S. O., Highland, M. J., Holt, M. V., Kim, D., Folkman, C. M., Thompson, C., Tripathi, A., Stephenson, G. B., Hong, S., Fuoss, P. H. 2013; 110 (17): 177601

    Abstract

    We used x-ray Bragg projection ptychography (BPP) to map spatial variations of ferroelectric polarization in thin film PbTiO3, which exhibited a striped nanoscale domain pattern on a high-miscut (001) SrTiO3 substrate. By converting the reconstructed BPP phase image to picometer-scale ionic displacements in the polar unit cell, a quantitative polarization map was made that was consistent with other characterization. The spatial resolution of 5.7 nm demonstrated here establishes BPP as an important tool for nanoscale ferroelectric domain imaging, especially in complex environments accessible with hard x rays.

    View details for DOI 10.1103/PhysRevLett.110.177601

    View details for Web of Science ID 000318188100019

    View details for PubMedID 23679778

  • Modular instrument mounting system for variable environment <i>in operando</i> X-ray experiments REVIEW OF SCIENTIFIC INSTRUMENTS Folkman, C. M., Highland, M. J., Perret, E., Kim, S. K., Fister, T. T., Zhou, H., Baldo, P. M., Seifert, S., Eastman, J. A., Fuoss, P. H., Fong, D. D. 2013; 84 (2): 025111

    Abstract

    In the growing field of in operando and in situ X-ray experiments, there exists a large disparity in the types of environments and equipment to control them. This situation makes it challenging to conduct multiple experiments with a single mechanical interface to the diffractometer. Here, we describe the design and implementation of a modular instrument mounting system that can be installed on a standard six-circle diffractometer (e.g., 5021 Huber GmbH). This new system allows for the rapid changeover of different chambers and sample heaters and permits accurate sample positioning (x, y, z, and azimuthal rotation) without rigid coupling to the chamber body. Isolation of the sample motion from the chamber enclosure is accomplished through a combination of custom rotary seals and bellows. Control of the pressure and temperature has been demonstrated in the ranges of 10(-6)-10(3) Torr and 25°C-900°C, respectively. We have utilized the system with several different modular instruments. As an example, we provide in situ sputtering results, where the growth dynamics of epitaxial LaGaO3 thin films on (001) SrTiO3 substrates were investigated.

    View details for DOI 10.1063/1.4791799

    View details for Web of Science ID 000316954600075

    View details for PubMedID 23464255

  • High Contrast X-ray Speckle from Atomic-Scale Order in Liquids and Glasses PHYSICAL REVIEW LETTERS Hruszkewycz, S. O., Sutton, M., Fuoss, P. H., Adams, B., Rosenkranz, S., Ludwig, K. F., Roseker, W., Fritz, D., Cammarata, M., Zhu, D., Lee, S., Lemke, H., Gutt, C., Robert, A., Gruebel, G., Stephenson, G. B. 2012; 109 (18): 185502

    Abstract

    The availability of ultrafast pulses of coherent hard x rays from the Linac Coherent Light Source opens new opportunities for studies of atomic-scale dynamics in amorphous materials. Here, we show that single ultrafast coherent x-ray pulses can be used to observe the speckle contrast in the high-angle diffraction from liquid Ga and glassy Ni(2)Pd(2)P and B(2)O(3). We determine the thresholds above which the x-ray pulses disturb the atomic arrangements. Furthermore, high contrast speckle is observed in scattering patterns from the glasses integrated over many pulses, demonstrating that the source and optics are sufficiently stable for x-ray photon correlation spectroscopy studies of dynamics over a wide range of time scales.

    View details for DOI 10.1103/PhysRevLett.109.185502

    View details for Web of Science ID 000310612000020

    View details for PubMedID 23215295

  • Quantitative Nanoscale Imaging of Lattice Distortions in Epitaxial Semiconductor Heterostructures Using Nanofocused X-ray Bragg Projection Ptychography NANO LETTERS Hruszkewycz, S. O., Holt, M. V., Murray, C. E., Bruley, J., Holt, J., Tripathi, A., Shpyrko, O. G., McNulty, I., Highland, M. J., Fuoss, P. H. 2012; 12 (10): 5148-5154

    Abstract

    We imaged nanoscale lattice strain in a multilayer semiconductor device prototype with a new X-ray technique, nanofocused Bragg projection ptychography. Applying this technique to the epitaxial stressor layer of a SiGe-on-SOI structure, we measured the internal lattice behavior in a targeted region of a single device and demonstrated that its internal strain profile consisted of two competing lattice distortions. These results provide the strongest nondestructive test to date of continuum modeling predictions of nanoscale strain distributions.

    View details for DOI 10.1021/nl303201w

    View details for Web of Science ID 000309615000014

    View details for PubMedID 22998744

  • Ultrafast Photovoltaic Response in Ferroelectric Nanolayers PHYSICAL REVIEW LETTERS Daranciang, D., Highland, M. J., Wen, H., Young, S. M., Brandt, N. C., Hwang, H. Y., Vattilana, M., Nicoul, M., Quirin, F., Goodfellow, J., Qi, T., Grinberg, I., Fritz, D. M., Cammarata, M., Zhu, D., Lemke, H. T., Walko, D. A., Dufresne, E. M., Li, Y., Larsson, J., Reis, D. A., Sokolowski-Tinten, K., Nelson, K. A., Rappe, A. M., Fuoss, P. H., Stephenson, G. B., Lindenberg, A. M. 2012; 108 (8)

    Abstract

    We show that light drives large-amplitude structural changes in thin films of the prototypical ferroelectric PbTiO3 via direct coupling to its intrinsic photovoltaic response. Using time-resolved x-ray scattering to visualize atomic displacements on femtosecond time scales, photoinduced changes in the unit-cell tetragonality are observed. These are driven by the motion of photogenerated free charges within the ferroelectric and can be simply explained by a model including both shift and screening currents, associated with the displacement of electrons first antiparallel to and then parallel to the ferroelectric polarization direction.

    View details for DOI 10.1103/PhysRevLett.108.087601

    View details for Web of Science ID 000300669600033

    View details for PubMedID 22463572

  • Equilibrium Polarization of Ultrathin PbTiO<sub>3</sub> with Surface Compensation Controlled by Oxygen Partial Pressure PHYSICAL REVIEW LETTERS Highland, M. J., Fister, T. T., Fong, D. D., Fuoss, P. H., Thompson, C., Eastman, J. A., Streiffer, S. K., Stephenson, G. B. 2011; 107 (18): 187602

    Abstract

    We present a synchrotron x-ray study of the equilibrium polarization structure of ultrathin PbTiO(3) films on SrRuO(3) electrodes epitaxially grown on SrTiO(3) (001) substrates, as a function of temperature and the external oxygen partial pressure (pO(2)) controlling their surface charge compensation. We find that the ferroelectric Curie temperature (T(C)) varies with pO(2) and has a minimum at the intermediate pO(2), where the polarization below T(C) changes sign. The experiments are in qualitative agreement with a model based on Landau theory that takes into account the interaction of the phase transition with the electrochemical equilibria for charged surface species. The paraelectric phase is stabilized at intermediate pO(2) when the concentrations of surface species are insufficient to compensate either polar orientation.

    View details for DOI 10.1103/PhysRevLett.107.187602

    View details for Web of Science ID 000296985900024

    View details for PubMedID 22107673

  • Framework for three-dimensional coherent diffraction imaging by focused beam x-ray Bragg ptychography OPTICS LETTERS Hruszkewycz, S. O., Holt, M. V., Tripathi, A., Maser, J., Fuoss, P. H. 2011; 36 (12): 2227-2229

    Abstract

    We present the framework for convergent beam Bragg ptychography, and, using simulations, we demonstrate that nanocrystals can be ptychographically reconstructed from highly convergent x-ray Bragg diffraction. The ptychographic iterative engine is extended to three dimensions and shown to successfully reconstruct a simulated nanocrystal using overlapping raster scans with a defocused curved beam, the diameter of which matches the crystal size. This object reconstruction strategy can serve as the basis for coherent diffraction imaging experiments at coherent scanning nanoprobe x-ray sources.

    View details for DOI 10.1364/OL.36.002227

    View details for Web of Science ID 000291722100018

    View details for PubMedID 21685975

  • Total-Reflection Inelastic X-Ray Scattering from a 10-nm Thick La<sub>0.6</sub>Sr<sub>0.4</sub>CoO<sub>3</sub> Thin Film PHYSICAL REVIEW LETTERS Fister, T. T., Fong, D. D., Eastman, J. A., Iddir, H., Zapol, P., Fuoss, P. H., Balasubramanian, M., Gordon, R. A., Balasubramaniam, K. R., Salvador, P. A. 2011; 106 (3): 037401

    Abstract

    To study equilibrium changes in composition, valence, and electronic structure near the surface and into the bulk, we demonstrate the use of a new approach, total-reflection inelastic x-ray scattering, as a sub-keV spectroscopy capable of depth profiling chemical changes in thin films with nanometer resolution. By comparing data acquired under total x-ray reflection and penetrating conditions, we are able to separate the O K-edge spectra from a 10 nm La0.6Sr0.4CoO3 thin film from that of the underlying SrTiO3 substrate. With a smaller wavelength probe than comparable soft x-ray absorption measurements, we also describe the ability to easily access dipole-forbidden final states, using the dramatic evolution of the La N4,5 edge with momentum transfer as an example.

    View details for DOI 10.1103/PhysRevLett.106.037401

    View details for Web of Science ID 000286742200019

    View details for PubMedID 21405295

  • The effect of exit beam phase aberrations on parallel beam coherent x-ray reconstructions REVIEW OF SCIENTIFIC INSTRUMENTS Hruszkewycz, S. O., Harder, R., Xiao, X., Fuoss, P. H. 2010; 81 (12): 123706

    Abstract

    Diffraction artifacts from imperfect x-ray windows near the sample are an important consideration in the design of coherent x-ray diffraction measurements. In this study, we used simulated and experimental diffraction patterns in two and three dimensions to explore the effect of phase imperfections in a beryllium window (such as a void or inclusion) on the convergence behavior of phasing algorithms and on the ultimate reconstruction. A predictive relationship between beam wavelength, sample size, and window position was derived to explain the dependence of reconstruction quality on beryllium defect size. Defects corresponding to this prediction cause the most damage to the sample exit wave and induce signature error oscillations during phasing that can be used as a fingerprint of experimental x-ray window artifacts. The relationship between x-ray window imperfection size and coherent x-ray diffractive imaging reconstruction quality explored in this work can play an important role in designing high-resolution in situ coherent imaging instrumentation and will help interpret the phasing behavior of coherent diffraction measured in these in situ environments.

    View details for DOI 10.1063/1.3514085

    View details for Web of Science ID 000285770800025

    View details for PubMedID 21198031

  • Polarization Switching without Domain Formation at the Intrinsic Coercive Field in Ultrathin Ferroelectric PbTiO<sub>3</sub> PHYSICAL REVIEW LETTERS Highland, M. J., Fister, T. T., Richard, M., Fong, D. D., Fuoss, P. H., Thompson, C., Eastman, J. A., Streiffer, S. K., Stephenson, G. 2010; 105 (16): 167601

    Abstract

    Polarization switching in ferroelectrics has been thought to occur only through the nucleation and growth of new domains. Here we use in situ synchrotron x-ray scattering to monitor switching controlled by applied chemical potential. In sufficiently thin PbTiO₃ films, nucleation is suppressed and switching occurs by a continuous mechanism, i.e., by uniform decrease and inversion of the polarization without domain formation. The observed lattice parameter shows that the electric field in the film during switching reaches the theoretical intrinsic coercive field.

    View details for DOI 10.1103/PhysRevLett.105.167601

    View details for Web of Science ID 000282816300023

    View details for PubMedID 21231014

  • Synchrotron x-ray diffraction measurements of strain in metallic nanoparticles with oxide shells JOURNAL OF PHYSICS D-APPLIED PHYSICS Ingham, B., Hendy, S. C., Fong, D. D., Fuoss, P. H., Eastman, J. A., Lassesson, A., Tee, K. C., Convers, P. Y., Brown, S. A., Ryan, M. P., Toney, M. F. 2010; 43 (7)

    View details for DOI 10.1088/0022-3727/43/7/075301

    View details for Web of Science ID 000274318200016

  • Reversible Chemical Switching of a Ferroelectric Film PHYSICAL REVIEW LETTERS Wang, R. V., Fong, D. D., Jiang, F., Highland, M. J., Fuoss, P. H., Thompson, C., Kolpak, A. M., Eastman, J. A., Streiffer, S. K., Rappe, A. M., Stephenson, G. B. 2009; 102 (4): 047601

    Abstract

    According to recent experiments and predictions, the orientation of the polarization at the surface of a ferroelectric material can affect its surface chemistry. Here we demonstrate the converse effect: the chemical environment can control the polarization orientation in a ferroelectric film. In situ synchrotron x-ray scattering measurements show that high or low oxygen partial pressure induces outward or inward polarization, respectively, in an ultrathin PbTiO3 film. Ab initio calculations provide insight into surface structure changes observed during chemical switching.

    View details for DOI 10.1103/PhysRevLett.102.047601

    View details for Web of Science ID 000262978600072

    View details for PubMedID 19257476

  • Particle size effect of hydrogen-induced lattice expansion of palladium nanoclusters PHYSICAL REVIEW B Ingham, B., Toney, M. F., Hendy, S. C., Cox, T., Fong, D. D., Eastman, J. A., Fuoss, P. H., Stevens, K. J., Lassesson, A., Brown, S. A., Ryan, M. P. 2008; 78 (24)

    View details for DOI 10.1103/PhysRevB.78.245408

    View details for Web of Science ID 000262246400075

  • Spontaneous oscillations and waves during chemical vapor deposition of InN PHYSICAL REVIEW LETTERS Jiang, F., Munkholm, A., Wang, R., Streiffer, S. K., Thompson, C., Fuoss, P. H., Latifi, K., Elder, K. R., Stephenson, G. B. 2008; 101 (8): 086102

    Abstract

    We report observations of self-sustaining spatiotemporal chemical oscillations during metal-organic chemical vapor deposition of InN onto GaN. Under constant supply of vapor precursors trimethylindium and NH3, the condensed-phase cycles between crystalline islands of InN and elemental In droplets. Propagating fronts between regions of InN and In occur with linear, circular, and spiral geometries. The results are described by a model in which the nitrogen activity produced by surface-catalyzed NH3 decomposition varies with the exposed surface areas of GaN, InN, and In.

    View details for DOI 10.1103/PhysRevLett.101.086102

    View details for Web of Science ID 000258643600049

    View details for PubMedID 18764640

  • X-ray diffuse scattering measurements of nucleation dynamics at femtosecond resolution PHYSICAL REVIEW LETTERS Lindenberg, A. M., Engemann, S., Gaffney, K. J., Sokolowski-Tinten, K., Larsson, J., Hillyard, P. B., Reis, D. A., Fritz, D. M., ARTHUR, J., Akre, R. A., George, M. J., Deb, A., Bucksbaum, P. H., Hajdu, J., Meyer, D. A., Nicoul, M., Blome, C., Tschentscher, T., Cavalieri, A. L., Falcone, R. W., Lee, S. H., Pahl, R., Rudati, J., Fuoss, P. H., Nelson, A. J., Krejcik, P., Siddons, D. P., Lorazo, P., Hastings, J. B. 2008; 100 (13)

    Abstract

    Femtosecond time-resolved small and wide angle x-ray diffuse scattering techniques are applied to investigate the ultrafast nucleation processes that occur during the ablation process in semiconducting materials. Following intense optical excitation, a transient liquid state of high compressibility characterized by large-amplitude density fluctuations is observed and the buildup of these fluctuations is measured in real time. Small-angle scattering measurements reveal snapshots of the spontaneous nucleation of nanoscale voids within a metastable liquid and support theoretical predictions of the ablation process.

    View details for DOI 10.1103/PhysRevLett.100.135502

    View details for Web of Science ID 000254670300046

    View details for PubMedID 18517965

  • Carrier-density-dependent lattice stability in InSb PHYSICAL REVIEW LETTERS Hillyard, P. B., Gaffney, K. J., Lindenberg, A. M., Engemann, S., Akre, R. A., ARTHUR, J., Blome, C., Bucksbaum, P. H., Cavalieri, A. L., Deb, A., Falcone, R. W., Fritz, D. M., Fuoss, P. H., Hajdu, J., Krejcik, P., Larsson, J., Lee, S. H., Meyer, D. A., Nelson, A. J., Pahl, R., Reis, D. A., Rudati, J., Siddons, D. P., Sokolowski-Tinten, K., von der Linde, D., Hastings, J. B. 2007; 98 (12)

    Abstract

    The ultrafast decay of the x-ray diffraction intensity following laser excitation of an InSb crystal has been utilized to observe carrier dependent changes in the potential energy surface. For the first time, an abrupt carrier dependent onset for potential energy surface softening and the appearance of accelerated atomic disordering for a very high average carrier density have been observed. Inertial dynamics dominate the early stages of crystal disordering for a wide range of carrier densities between the onset of crystal softening and the appearance of accelerated atomic disordering.

    View details for DOI 10.1103/PhysRevLett.98.125501

    View details for PubMedID 17501133

  • Ultrafast bond softening in bismuth: Mapping a solid's interatomic potential with X-rays SCIENCE Fritz, D. M., Reis, D. A., Adams, B., Akre, R. A., ARTHUR, J., Blome, C., Bucksbaum, P. H., Cavalieri, A. L., Engemann, S., Fahy, S., Falcone, R. W., Fuoss, P. H., Gaffney, K. J., George, M. J., Hajdu, J., Hertlein, M. P., Hillyard, P. B., Hoegen, M. H., Kammler, M., Kaspar, J., Kienberger, R., Krejcik, P., Lee, S. H., Lindenberg, A. M., McFarland, B., Meyer, D., Montagne, T., Murray, E. D., Nelson, A. J., Nicoul, M., Pahl, R., Rudati, J., Schlarb, H., Siddons, D. P., Sokolowski-Tinten, K., Tschentscher, T., von der Linde, D., Hastings, J. B. 2007; 315 (5812): 633-636

    Abstract

    Intense femtosecond laser excitation can produce transient states of matter that would otherwise be inaccessible to laboratory investigation. At high excitation densities, the interatomic forces that bind solids and determine many of their properties can be substantially altered. Here, we present the detailed mapping of the carrier density-dependent interatomic potential of bismuth approaching a solid-solid phase transition. Our experiments combine stroboscopic techniques that use a high-brightness linear electron accelerator-based x-ray source with pulse-by-pulse timing reconstruction for femtosecond resolution, allowing quantitative characterization of the interatomic potential energy surface of the highly excited solid.

    View details for DOI 10.1126/science.1135009

    View details for Web of Science ID 000243909400039

    View details for PubMedID 17272718

  • Detectors for ultrafast X-ray experiments at SPPS SYNCHROTRON RADIATION INSTRUMENTATION, PTS 1 AND 2 Siddons, D. P., Kuczewski, A. J., Yu, B., Warren, J., Rudati, J., Fuoss, P., Hastings, J. B., Kaspar, J. D., Meyer, D. A. 2007; 879: 1176-?

    View details for Web of Science ID 000244647900282

  • Stabilization of monodomain polarization in ultrathin PbTiO<sub>3</sub> films PHYSICAL REVIEW LETTERS Fong, D. D., Kolpak, A. M., Eastman, J. A., Streiffer, S. K., Fuoss, P. H., Stephenson, G. B., Thompson, C., Kim, D. M., Choi, K. J., Eom, C. B., Grinberg, Rappe, A. M. 2006; 96 (12): 127601

    Abstract

    Using in situ high-resolution synchrotron x-ray scattering, the Curie temperature TC has been determined for ultrathin c-axis epitaxial PbTiO3 films on conducting substrates (SrRuO3 on SrTiO3), with surfaces exposed to a controlled vapor environment. The suppression of TC was relatively small, even for the thinnest film (1.2 nm). We observe that 180 degrees stripe domains do not form, indicating that the depolarizing field is compensated by free charge at both interfaces. This is confirmed by ab initio calculations that find polar ground states in the presence of ionic adsorbates.

    View details for DOI 10.1103/PhysRevLett.96.127601

    View details for Web of Science ID 000236467000075

    View details for PubMedID 16605959

  • Observation of structural anisotropy and the onset of liquidlike motion during the nonthermal melting of InSb PHYSICAL REVIEW LETTERS Gaffney, K. J., Lindenberg, A. M., Larsson, J., Sokolowski-Tinten, K., Blome, C., Synnergren, O., Sheppard, J., Caleman, C., MacPhee, A. G., Weinstein, D., Lowney, D. P., Allison, T., Matthews, T., Falcone, R. W., Cavalieri, A. L., Fritz, D. M., Lee, S. H., Bucksbaum, P. H., Reis, D. A., Rudati, J., Macrander, A. T., Fuoss, P. H., Kao, C. C., Siddons, D. P., Pahl, R., Moffat, K., Als-Nielsen, J., Duesterer, S., Ischebeck, R., Schlarb, H., Schulte-Schrepping, H., Schneider, J., von der Linde, D., Hignette, O., Sette, F., Chapman, H. N., Lee, R. W., Hansen, T. N., Wark, J. S., Bergh, M., Huldt, G., van der Spoel, D., Timneanu, N., Hajdu, J., Akre, R. A., Bong, E., Krejcik, P., ARTHUR, J., Brennan, S., Luening, K., Hastings, J. B. 2005; 95 (12)

    Abstract

    The melting dynamics of laser excited InSb have been studied with femtosecond x-ray diffraction. These measurements observe the delayed onset of diffusive atomic motion, signaling the appearance of liquidlike dynamics. They also demonstrate that the root-mean-squared displacement in the [111] direction increases faster than in the [110] direction after the first 500 fs. This structural anisotropy indicates that the initially generated fluid differs significantly from the equilibrium liquid.

    View details for DOI 10.1103/PhysRevLett.95.125701

    View details for Web of Science ID 000231908200033

    View details for PubMedID 16197085

  • Atomic-scale visualization of inertial dynamics SCIENCE Lindenberg, A. M., Larsson, J., Sokolowski-Tinten, K., Gaffney, K. J., Blome, C., Synnergren, O., Sheppard, J., Caleman, C., MacPhee, A. G., Weinstein, D., Lowney, D. P., Allison, T. K., Matthews, T., Falcone, R. W., Cavalieri, A. L., Fritz, D. M., Lee, S. H., Bucksbaum, P. H., Reis, D. A., Rudati, J., Fuoss, P. H., Kao, C. C., Siddons, D. P., Pahl, R., Als-Nielsen, J., Duesterer, S., Ischebeck, R., Schlarb, H., Schulte-Schrepping, H., Tschentscher, T., Schneider, J., von der Linde, D., Hignette, O., Sette, F., Chapman, H. N., Lee, R. W., Hansen, T. N., Techert, S., Wark, J. S., Bergh, M., Huldt, G., van der Spoel, D., Timneanu, N., Hajdu, J., Akre, R. A., Bong, E., Krejcik, P., ARTHUR, J., Brennan, S., Luening, K., Hastings, J. B. 2005; 308 (5720): 392-395

    Abstract

    The motion of atoms on interatomic potential energy surfaces is fundamental to the dynamics of liquids and solids. An accelerator-based source of femtosecond x-ray pulses allowed us to follow directly atomic displacements on an optically modified energy landscape, leading eventually to the transition from crystalline solid to disordered liquid. We show that, to first order in time, the dynamics are inertial, and we place constraints on the shape and curvature of the transition-state potential energy surface. Our measurements point toward analogies between this nonequilibrium phase transition and the short-time dynamics intrinsic to equilibrium liquids.

    View details for DOI 10.1126/science.1107996

    View details for Web of Science ID 000228492000046

    View details for PubMedID 15831753

  • Clocking femtosecond x rays PHYSICAL REVIEW LETTERS Cavalieri, A. L., Fritz, D. M., Lee, S. H., Bucksbaum, P. H., Reis, D. A., Rudati, J., Mills, D. M., Fuoss, P. H., Stephenson, G. B., Kao, C. C., Siddons, D. P., Lowney, D. P., MacPhee, A. G., Weinstein, D., Falcone, R. W., Pahl, R., Als-Nielsen, J., Blome, C., Dusterer, S., Ischebeck, R., Schlarb, H., Schulte-Schrepping, H., Tschentscher, T., Schneider, J., Hignette, O., Sette, F., Sokolowski-Tinten, K., Chapman, H. N., Lee, R. W., Hansen, T. N., Synnergren, O., Larsson, J., Techert, S., Sheppard, J., Wark, J. S., Bergh, M., Caleman, C., Huldt, G., van der Spoel, D., Timneanu, N., Hajdu, J., Akre, R. A., Bong, E., Emma, P., Krejcik, P., ARTHUR, J., Brennan, S., Gaffney, K. J., Lindenberg, A. M., Luening, K., Hastings, J. B. 2005; 94 (11)

    Abstract

    Linear-accelerator-based sources will revolutionize ultrafast x-ray science due to their unprecedented brightness and short pulse duration. However, time-resolved studies at the resolution of the x-ray pulse duration are hampered by the inability to precisely synchronize an external laser to the accelerator. At the Sub-Picosecond Pulse Source at the Stanford Linear-Accelerator Center we solved this problem by measuring the arrival time of each high energy electron bunch with electro-optic sampling. This measurement indirectly determined the arrival time of each x-ray pulse relative to an external pump laser pulse with a time resolution of better than 60 fs rms.

    View details for DOI 10.1103/PhysRevLett.94.114801

    View details for Web of Science ID 000227923200034

    View details for PubMedID 15903864

  • <i>In situ</i> synchrotron X-ray studies of ferroelectric thin films Fong, D. D., Eastman, J. A., Stephenson, G. B., Fuoss, P. H., Streiffer, S. K., Thompson, C., Auciello, O. INT UNION CRYSTALLOGRAPHY. 2005: 163-167

    Abstract

    In situ synchrotron X-ray scattering was used to observe both the growth of PbTiO3 films by metal-organic chemical vapour deposition and the behaviour of the ferroelectric phase transition as a function of film thickness. The dependences of growth mode and deposition rate on gas flows and substrate temperature were determined by homoepitaxial growth studies on thick films (>50 nm). These studies facilitated the growth of thin coherently strained PbTiO3 films on SrTiO3 (001) substrates, with thicknesses ranging from 2 to 42 nm. Experiments on the ferroelectric phase transition as a function of film thickness were carried out in these films under controlled mechanical and electrical boundary conditions.

    View details for DOI 10.1107/S0909049504025816

    View details for Web of Science ID 000227377200006

    View details for PubMedID 15728968

  • Ferroelectricity in ultrathin perovskite films SCIENCE Fong, D. D., Stephenson, G. B., Streiffer, S. K., Eastman, J. A., Auciello, O., Fuoss, P. H., Thompson, C. 2004; 304 (5677): 1650-1653

    Abstract

    Understanding the suppression of ferroelectricity in perovskite thin films is a fundamental issue that has remained unresolved for decades. We report a synchrotron x-ray study of lead titanate as a function of temperature and film thickness for films as thin as a single unit cell. At room temperature, the ferroelectric phase is stable for thicknesses down to 3 unit cells (1.2 nanometers). Our results imply that no thickness limit is imposed on practical devices by an intrinsic ferroelectric size effect.

    View details for DOI 10.1126/science.1098252

    View details for Web of Science ID 000221934300044

    View details for PubMedID 15192223

  • Silicon-induced faceting of vicinal GaAs(001) JOURNAL OF APPLIED PHYSICS Brennan, S., Stephenson, G. B., Fuoss, P. H., Kisker, D. W., Lavoie, C., Evans-Lutterodt, K. L. 2000; 88 (6): 3367-3376

    View details for Web of Science ID 000089034700033

  • Optical characterization of surfaces during epitaxial growth using RDS and GIXS JOURNAL OF CRYSTAL GROWTH Kamiya, I., Mantese, L., Aspnes, D. E., Kisker, D. W., Fuoss, P. H., Stephenson, G. B., Brennan, S. 1996; 163 (1-2): 67-77

    View details for Web of Science ID A1996UQ84600010

  • Atomic scale studies of epitaxial growth processes using X-ray techniques Kisker, D. W., Stephenson, G. B., Tersoff, J., Fuoss, P. H., Brennan, S. ELSEVIER SCIENCE BV. 1996: 54-59

    View details for DOI 10.1016/0022-0248(95)01049-1

    View details for Web of Science ID A1996UQ84600008

  • Investigation of the relationship between reflectance difference spectroscopy and surface structure using grazing incidence X-ray scattering Kisker, D. W., Stephenson, G. B., Kamiya, Fuoss, P. H., Aspnes, D. E., Mantese, L., Brennan, S. AKADEMIE VERLAG GMBH. 1995: 9-21

    View details for DOI 10.1002/pssa.2211520102

    View details for Web of Science ID A1995TN96700001

  • IN-SITU X-RAY STUDIES OF ORGANOMETALLIC VAPOR-PHASE EPITAXY GROWTH MATERIALS SCIENCE AND ENGINEERING B-SOLID STATE MATERIALS FOR ADVANCED TECHNOLOGY Fuoss, P. H., Kisker, D. W., Stephenson, G. B., Brennan, S. 1995; 30 (2-3): 99-108

    View details for Web of Science ID A1995QQ69000005

  • CHARACTERIZATION OF VAPOR-PHASE GROWTH USING X-RAY TECHNIQUES KISKER, D. W., STEPHENSON, G. B., FUOSS, P. H., BRENNAN, S. ELSEVIER SCIENCE BV. 1995: 104-111

    View details for DOI 10.1016/0022-0248(94)00588-5

    View details for Web of Science ID A1995QD18700019

  • GAAS C(4X4) SURFACE-STRUCTURE IN ORGANOMETALLIC VAPOR-PHASE EPITAXY PHYSICAL REVIEW B Payne, A. P., Fuoss, P. H., Kisker, D. W., Stephenson, G. B., Brennan, S. 1994; 49 (20): 14427-14434

    View details for Web of Science ID A1994NR42300038

    View details for PubMedID 10010525

  • X-RAY-SCATTERING ANALYSIS OF SURFACE-STRUCTURES PRODUCED BY VAPOR-PHASE EPITAXY OF GAAS PHYSICAL REVIEW B Lamelas, F. J., Fuoss, P. H., Kisker, D. W., Stephenson, G. B., Imperatori, P., Brennan, S. 1994; 49 (3): 1957-1965

    View details for Web of Science ID A1994MW69400055

    View details for PubMedID 10010997

  • TIME-RESOLVED X-RAY-SCATTERING STUDIES OF LAYER-BY-LAYER EPITAXIAL-GROWTH PHYSICAL REVIEW LETTERS Fuoss, P. H., Kisker, D. W., Lamelas, F. J., Stephenson, G. B., Imperatori, P., Brennan, S. 1992; 69 (19): 2791-2794

    View details for Web of Science ID A1992JX24500015

    View details for PubMedID 10046590

  • ATOMIC SCALE CHARACTERIZATION OF ORGANOMETALLIC VAPOR-PHASE EPITAXIAL-GROWTH USING INSITU GRAZING-INCIDENCE X-RAY-SCATTERING KISKER, D. W., STEPHENSON, G. B., FUOSS, P. H., LAMELAS, F. J., BRENNAN, S., IMPERATORI, P. ELSEVIER SCIENCE BV. 1992: 1-9

    View details for DOI 10.1016/0022-0248(92)90429-M

    View details for Web of Science ID A1992KB90500002

  • GALLIUM-ARSENIDE SURFACE RECONSTRUCTIONS DURING ORGANOMETALLIC VAPOR-PHASE EPITAXY APPLIED PHYSICS LETTERS Lamelas, F. J., Fuoss, P. H., Imperatori, P., Kisker, D. W., Stephenson, G. B., Brennan, S. 1992; 60 (21): 2610-2612

    View details for Web of Science ID A1992HV49100012

  • X-RAY-SCATTERING STUDIES OF INTERMEDIATE-RANGE ORDER IN AMORPHOUS GESE2 JOURNAL OF NON-CRYSTALLINE SOLIDS FISCHERCOLBRIE, A., FUOSS, P. H. 1990; 126 (1-2): 1-34

    View details for DOI 10.1016/0022-3093(90)91020-R

    View details for Web of Science ID A1990EM81800001

  • EXPERIMENTAL CONSIDERATIONS FOR INSITU X-RAY-SCATTERING ANALYSIS OF OMVPE GROWTH 6TH NATIONAL CONF ON SYNCHROTRON RADIATION INSTRUMENTATION Brennan, S., Fuoss, P. H., Kahn, J. L., Kisker, D. W. ELSEVIER SCIENCE BV. 1990: 86–92

    View details for Web of Science ID A1990DL89700016

  • X-RAY-ANALYSIS OF GAAS SURFACE RECONSTRUCTIONS IN H2 AND N2 ATMOSPHERES APPLIED PHYSICS LETTERS Kisker, D. W., Fuoss, P. H., TOKUDA, K. L., Renaud, G., Brennan, S., Kahn, J. L. 1990; 56 (20): 2025-2027

    View details for Web of Science ID A1990DC93500033

  • INSITU CHARACTERIZATION OF ORGANOMETALLIC GROWTH OF ZNSE USING GRAZING-INCIDENCE X-RAY-SCATTERING 4TH INTERNATIONAL CONF ON II-VI COMPOUNDS ( II-VI-89 ) Kisker, D. W., Fuoss, P. H., Brennan, S., Renaud, G., TOKUDA, K. L., Kahn, J. L. ELSEVIER SCIENCE BV. 1990: 42–47

    View details for Web of Science ID A1990DP34300008

  • SURFACE SENSITIVE X-RAY-SCATTERING ANNUAL REVIEW OF MATERIALS SCIENCE Fuoss, P. H., Brennan, S. 1990; 20: 365-390

    View details for Web of Science ID A1990DR86400015

  • ATOMIC NATURE OF ORGANOMETALLIC-VAPOR-PHASE-EPITAXIAL GROWTH PHYSICAL REVIEW LETTERS Fuoss, P. H., Kisker, D. W., Renaud, G., TOKUDA, K. L., Brennan, S., Kahn, J. L. 1989; 63 (21): 2389-2392

    View details for Web of Science ID A1989AZ86600019

  • THE SI(001)/SIO2 INTERFACE APPLIED SURFACE SCIENCE OURMAZD, A., FUOSS, P. H., BEVK, J., MORAR, J. F. 1989; 41-2: 365-371

    View details for DOI 10.1016/0169-4332(89)90086-X

    View details for Web of Science ID A1989CE22000060

  • HG1-XCDXTE/HG1-XZNXTE SUPERLATTICES WITH CONSTANT HG CONTENT APPLIED PHYSICS LETTERS Feldman, R. D., Fuoss, P. H., Austin, R. F., Kahn, J. L., Norton, L. J., Brennan, S. 1989; 54 (15): 1466-1468

    View details for Web of Science ID A1989U019400029

  • STRUCTURE AND BONDING IN PHOTODIFFUSED AMORPHOUS AG-GESE2 THIN-FILMS PHYSICAL REVIEW B FISCHERCOLBRIE, A., Bienenstock, A., Fuoss, P. H., Marcus, M. A. 1988; 38 (17): 12388-12403

    View details for Web of Science ID A1988R366800040

  • STRUCTURE OF ALPHA-GESE2 FROM X-RAY-SCATTERING MEASUREMENTS PHYSICAL REVIEW B FUOSS, P. H., FISCHERCOLBRIE, A. 1988; 38 (3): 1875-1878

    View details for DOI 10.1103/PhysRevB.38.1875

    View details for Web of Science ID A1988P463800032

    View details for PubMedID 9946472

  • X-RAY-SCATTERING STUDIES OF THE MELTING OF LEAD SURFACES PHYSICAL REVIEW LETTERS Fuoss, P. H., Norton, L. J., Brennan, S. 1988; 60 (20): 2046-2049

    View details for Web of Science ID A1988N387300015

    View details for PubMedID 10038243

  • X-RAY-SCATTERING STUDIES OF THE SI-SIO2 INTERFACE PHYSICAL REVIEW LETTERS Fuoss, P. H., Norton, L. J., Brennan, S., FISCHERCOLBRIE, A. 1988; 60 (7): 600-603

    View details for Web of Science ID A1988M021900014

    View details for PubMedID 10038594

  • PHASE-SEPARATION IN CD1-XZNXTE GROWN BY MOLECULAR-BEAM EPITAXY JOURNAL OF VACUUM SCIENCE & TECHNOLOGY B Feldman, R. D., Austin, R. F., Fuoss, P. H., DAYEM, A. H., WESTERWICK, E. H., Nakahara, S., Boone, T., Menendez, J., Pinczuk, A., Valladares, J. P., Brennan, S. 1987; 5 (3): 690-693

    View details for Web of Science ID A1987H664400015

  • STRUCTURAL STUDIES OF AMORPHOUS MATERIALS USING SYNCHROTRON RADIATION AND ANOMALOUS SCATTERING Bienenstock, A., FISCHERCOLBRJE, A., Kortright, J., Lorentz, R., Ludwig, K., Warburton, W., Wilson, L., Fuoss, P. WILEY-BLACKWELL. 1984: C399–C399

    View details for Web of Science ID A1984TK54501152

  • X-RAY RDF ANALYSIS OF 1500 A THICK AMORPHOUS FILMS JOURNAL OF NON-CRYSTALLINE SOLIDS FISCHERCOLBRIE, A., FUOSS, P. H. 1983; 59-6 (DEC): 859-862

    View details for Web of Science ID A1983RZ94400049

  • APPLICATION OF DIFFERENTIAL ANOMALOUS X-RAY-SCATTERING TO STRUCTURAL STUDIES OF AMORPHOUS MATERIALS PHYSICAL REVIEW LETTERS Fuoss, P. H., Eisenberger, P., Warburton, W. K., Bienenstock, A. 1981; 46 (23): 1537-1540

    View details for Web of Science ID A1981LT17900012

  • A PHASE-DIFFERENCE APPROACH TO EXAFS ANALYSIS OF GERMANIUM POLYMORPHS ACTA CRYSTALLOGRAPHICA SECTION A KAWAMURA, T., SHIMOMURA, O., FUKAMACHI, T., FUOSS, P. H. 1981; 37 (SEP): 653-658

    View details for DOI 10.1107/S0567739481001496

    View details for Web of Science ID A1981MG96900009

  • ANOMALOUS SCATTERING DETERMINATIONS OF THE PAIR DISTRIBUTION-FUNCTIONS IN AMORPHOUS GESE JOURNAL OF NON-CRYSTALLINE SOLIDS Fuoss, P. H., Warburton, W. K., Bienenstock, A. 1980; 35-6 (JAN-): 1233-1238

    View details for Web of Science ID A1980JD13100093

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