@article{burnette_kiesel_sayers_nemanich_2008, title={Titanium Interlayer Mediated Epitaxy of CoSi2 on Si1-xGex}, volume={516}, ISSN={["0040-6090"]}, DOI={10.1016/j.tsf.2007.08.045}, abstractNote={Abstract Titanium Interlayer Mediated Epitaxy (TIME) has been shown to promote the formation of epitaxial CoSi2 on Si (100). Similarities between Si and Si1−xGex alloys have motivated a study of whether the TIME process could be successful in forming epitaxial CoSi2 on Si1−xGex. Titanium layers of varying thickness were deposited as interlayers between a Co layer and c-Si/Si0.8Ge0.2 grown epitaxially onto Si (100) to investigate their role in the formation of epitaxial CoSi2 on Si1−xGex alloys. The effect of Ti interlayer thickness on the orientation of CoSi2 to the Si1−xGex substrate, and the conditions under which a polycrystalline CoSi2 film has been formed have been studied. It was found that Ti was beneficial in promoting epitaxy to the substrate in all cases. The experimental results indicate that with a Ti interlayer thickness of ∼ 50 A, the formation of epitaxial CoSi2 adjacent to the substrate was achieved, and pinhole formation was minimized. It was also observed that for increased interlayer thickness, Ti reacted with Si to form a titanium silicide.}, number={8}, journal={THIN SOLID FILMS}, author={Burnette, James E. and Kiesel, Sharon and Sayers, Dale E. and Nemanich, Robert J.}, year={2008}, month={Feb}, pages={1809–1817} }
 @misc{bazin_sayers_lynch_guczi_treglia_mottet_2006, title={Combining solid state physics concepts and X-ray absorption Spectroscopy to understand DeNO(x) catalysis}, volume={61}, number={5}, journal={Oil & Gas Science and Technology}, author={Bazin, D. and Sayers, D. and Lynch, J. and Guczi, L. and Treglia, G. and Mottet, C.}, year={2006}, pages={677–689} }
 @article{connor_sayers_sumner_zhong_2006, title={Diffraction enhanced imaging of controlled defects within bone, including bone-metal gaps}, volume={51}, number={12}, journal={Physics in Medicine & Biology}, author={Connor, D. M. and Sayers, D. and Sumner, D. R. and Zhong, Z.}, year={2006}, pages={3283–3300} }
 @article{burnette_nemanich_sayers_2005, title={Formation of stable titanium germanosilicide thin films on Si1-xGex}, volume={97}, ISSN={["1089-7550"]}, DOI={10.1063/1.1923164}, abstractNote={The sequential deposition of strained Si1−xGex with concentrations x=0.20 and 0.30, amorphous silicon, and titanium on Si (100) after annealing at 700°C leads to the formation of a C54 Ti(Si1−yGey)2∕Si1−xGex bilayer, the phase formation and interface stability of which are studied. The use of an amorphous layer of Si is employed to eliminate or decrease the formation of germanium-rich Si1−zGez alloy precipitates found in the solid-phase reaction of Ti and Si1−xGex. It has been proposed that the precipitation phenomenon was driven by differences in the enthalpy of formation as a function of concentration in the Ti(Si1−yGey)2 layer, resulting from the enthalpy difference between TiSi2 and TiGe2 compounds, both of which are assumed to be completely miscible with one another. Layers of amorphous silicon of varying thicknesses were incorporated between a 300-A Ti layer and the strained Si1−xGex substrate layer to achieve Ti(Si1−yGey)2 films that are in equilibrium with the Si1−xGex substrate. The use of amorph...}, number={11}, journal={JOURNAL OF APPLIED PHYSICS}, author={Burnette, JE and Nemanich, RJ and Sayers, DE}, year={2005}, month={Jun} }
 @article{connor_sayers_sumner_zhong_2005, title={Identification of fatigue damage in cortical bone by diffraction enhanced imaging}, volume={548}, ISSN={["1872-9576"]}, DOI={10.1016/j.nima.2005.03.095}, abstractNote={In an effort to explore Diffraction Enhanced Imaging of bone tissue, experiments were performed to determine if it was possible to use Diffraction Enhanced Imaging to detect microdamage in bovine cortical bone. Measurements were made at the National Synchrotron Light Source where pre- and post-fatigue rocking curve widths of the bone were studied. The rocking curve widths were then compared. Since no consistent pattern of narrowing or broadening of the rocking curve emerged, it is likely that the ultra-small-angle X-ray scattering present in the bone overshadowed any additional changes to rocking curve caused by microdamage of the bone. Larger bone structures were able to be visualized which suggests that microdamage may be visualized with a higher resolution detector.}, number={1-2}, journal={NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS AND ASSOCIATED EQUIPMENT}, author={Connor, DM and Sayers, D and Sumner, DR and Zhong, Z}, year={2005}, month={Aug}, pages={234–239} }
 @article{kiss_sayers_zhong_parham_pisano_2004, title={Improved image contrast of calcifications in breast tissue specimens using diffraction enhanced imaging}, volume={49}, number={15}, journal={Physics in Medicine & Biology}, author={Kiss, M. Z. and Sayers, D. E. and Zhong, Z. and Parham, C. and Pisano, E. D.}, year={2004}, pages={3427–3439} }
 @misc{chapman_hasnah_oltulu_zhong_mollenhauer_c._k._m._e. d._r. e._et al._2003, title={Diffraction enhanced x-ray imaging of articular cartilage}, volume={6577708}, publisher={Washington, DC: U.S. Patent and Trademark Office}, author={Chapman, L. D. and Hasnah, M. O. and Oltulu, O. and Zhong, Z. and Mollenhauer, J. Muehleman and C., Kuettner and K., Aurich and M., Pisano and E. D., Johnston and R. E., Thomlinson and et al.}, year={2003} }
 @article{kiss_sayers_zhong_2003, title={Measurement of image contrast using diffraction enhanced imaging}, volume={48}, number={3}, journal={Physics in Medicine & Biology}, author={Kiss, M. Z. and Sayers, D. E. and Zhong, Z.}, year={2003}, pages={325–340} }
 @article{beauchemin_hesterberg_chou_beauchemin_simard_sayers_2003, title={Speciation of phosphorus in phosphorus-enriched agricultural soils using X-ray absorption near-edge structure spectroscopy and chemical fractionation}, volume={32}, ISSN={["0047-2425"]}, DOI={10.2134/jeq2003.1809}, abstractNote={Knowledge of phosphorus (P) species in P-rich soils is useful for assessing P mobility and potential transfer to ground water and surface waters. Soil P was studied using synchrotron X-ray absorption near-edge structure (XANES) spectroscopy (a nondestructive chemical-speciation technique) and sequential chemical fractionation. The objective was to determine the chemical speciation of P in long-term-fertilized, P-rich soils differing in pH, clay, and organic matter contents. Samples of three slightly acidic (pH 5.5-6.2) and two slightly alkaline (pH 7.4-7.6) soils were collected from A or B horizons in two distinct agrosystems in the province of Québec, Canada. The soils contained between 800 and 2100 mg total P kg(-1). Distinct XANES features for Ca-phosphate mineral standards and for standards of adsorbed phosphate made it possible to differentiate these forms of P in the soil samples. The XANES results indicated that phosphate adsorbed on Fe- or Al-oxide minerals was present in all soils, with a higher proportion in acidic than in slightly alkaline samples. Calcium phosphate also occurred in all soils, regardless of pH. In agreement with chemical fractionation results, XANES data showed that Ca-phosphates were the dominant P forms in one acidic (pH 5.5) and in the two slightly alkaline (pH 7.4-7.6) soil samples. X-ray absorption near-edge structure spectroscopy directly identified certain forms of soil P, while chemical fractionation provided indirect supporting data and gave insights on additional forms of P such as organic pools that were not accounted for by the XANES analyses.}, number={5}, journal={JOURNAL OF ENVIRONMENTAL QUALITY}, author={Beauchemin, S and Hesterberg, D and Chou, J and Beauchemin, M and Simard, RR and Sayers, DE}, year={2003}, pages={1809–1819} }
 @article{kiss_sayers_zhong_2002, title={Comparison of X-ray detectors for a diffraction enhanced imaging system}, volume={491}, ISSN={["1872-9576"]}, DOI={10.1016/S0168-9002(02)01125-7}, abstractNote={Three digital detector systems—a Fuji BAS2500 Image Plate Reader, a prototype charge-coupled device (CCD) from Mar USA and the MicroPhotonics XQUIS 1000 were compared with respect to format, dynamic range, dark noise, and spatial resolution. Experiments were conducted using highly collimated monochromatic X-rays at 20 keV, produced at the National Synchrotron Light Source. This study characterized digital detectors being considered for integration into a synchrotron-based diffraction enhanced imaging (DEI) apparatus used for medical imaging research, particularly mammography. These detectors are also being considered for integration into a proposed clinical prototype for DEI-based mammography. While all three systems had comparable image quality, the CCDs had faster readout time than the image plate system. However, the Fuji system had the largest dynamic range (∼10 5 compared to 10 4 for CCDs) and the largest active area. The MicroPhotonics XQUIS 1000 had the best spatial resolution as characterized by the point spread function.}, number={1-2}, journal={NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS AND ASSOCIATED EQUIPMENT}, author={Kiss, MZ and Sayers, DE and Zhong, Z}, year={2002}, month={Sep}, pages={280–290} }
 @article{hasnah_zhong_oltulu_pisano_johnston_sayers_thomlinson_chapman_2002, title={Diffraction enhanced imaging contrast mechanisms in breast cancer specimens}, volume={29}, ISSN={["0094-2405"]}, DOI={10.1118/1.1507782}, abstractNote={We have investigated the contrast mechanisms of the refraction angle, and the apparent absorption images obtained from the diffraction enhanced imaging technique (DEI) and have correlated them with the absorption contrast of conventional radiography. The contrast of both the DEI refraction angle image and the radiograph have the same dependence on density differences of the tissues in the visualization of cancer; in radiography these differences directly relate to the contrast while in the DEI refraction angle image it is the density difference and thickness gradient that gives the refraction angle. We show that the density difference of fibrils in breast cancer as measured by absorption images correlate well with the density difference derived from refraction angle images of DEI. In addition we find that the DEI apparent absorption image and the image obtained with the DEI system at the top of the reflectivity curve have much greater contrast than that of the normal radiograph (x8 to 33-fold higher). This is due to the rejection of small angle scattering (extinction) from the fibrils enhancing the contrast.}, number={10}, journal={MEDICAL PHYSICS}, author={Hasnah, MO and Zhong, Z and Oltulu, O and Pisano, E and Johnston, RE and Sayers, D and Thomlinson, W and Chapman, D}, year={2002}, month={Oct}, pages={2216–2221} }
 @article{platow_oh_nemanich_sayers_hartman_davis_2002, title={TiC nanoisland formation on 6H-SiC(0001)(Si)}, volume={91}, ISSN={["0021-8979"]}, DOI={10.1063/1.1465121}, abstractNote={Spontaneous formation of titanium carbide nanoislands on silicon carbide substrates has been studied with scanning tunneling microscopy and x-ray absorption near-edge spectroscopy. Scratch-free and atomically flat 6H–SiC(0001)Si substrates were prepared by high temperature hydrogen etching. The surfaces were subsequently cleaned by in situ ultrahigh vacuum annealing. Titanium carbide nanoislands were formed by titanium deposition and annealing at 950 °C. The average width (10–50 nm) and separation of the Ti islands was controlled by varying the titanium coverage (0.1–0.3 nm) and the annealing time (1–20 min). At the lowest coverage, the islands were uniformly distributed over the surface, while at higher coverage the islands tended to collect at the substrate step edges.}, number={9}, journal={JOURNAL OF APPLIED PHYSICS}, author={Platow, W and Oh, J and Nemanich, RJ and Sayers, DE and Hartman, JD and Davis, RF}, year={2002}, month={May}, pages={6081–6084} }
 @article{hesterberg_chou_hutchison_sayers_2001, title={Bonding of Hg(II) to reduced organic, sulfur in humic acid as affected by S/Hg ratio}, volume={35}, ISSN={["1520-5851"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-0035387905&partnerID=MN8TOARS}, DOI={10.1021/es001960o}, abstractNote={Organic matter is an important sorbent of heavy metals in soils and sediments. The heterogeneity of organic matter, including the presence of various reactive O-, N-, and S-bearing ligands, makes it difficult to precisely characterize the nature of metal-ligand binding sites. The objective of this research was to characterize the extent and nature of Hg(II) bonding with reduced organic S in soil organic matter. Sulfur-rich humic acid (0.7 +/- 0.1 mol of S kg-1) was extracted from samples of surface soil from a marine wetland. Synchrotron X-ray absorption near-edge structure (XANES) analysis at the S K edge indicated that 70 +/- 3 mol % of the organic S was in a reduced oxidation state. Aqueous solutions containing 2 mmol of Hg kg-1, 0.1 M NaNO3, and humic acid added at various S/Hg molar ratios at pH 5.60 +/- 0.02 were characterized using extended X-ray absorption fine structure (EXAFS) spectroscopy at the Hg LIII edge. Spectral fitting showed that as the total S/Hg ratio increased from 0.6 to 5.6 (reduced S/Hg of 0.4-4.0), the fraction of Hg-S bonding relative to Hg-O (or Hg-N) bonding increased from 0.4 to 0.9. Results demonstrated preferential bonding of Hg(II) to reduced organic S sites and indicated that multiple sulfur ligands were coordinated with Hg2+ ions at high S/Hg ratios, which corresponded to low levels of complexed Hg(II).}, number={13}, journal={ENVIRONMENTAL SCIENCE & TECHNOLOGY}, author={Hesterberg, D and Chou, JW and Hutchison, KJ and Sayers, DE}, year={2001}, month={Jul}, pages={2741–2745} }
 @article{lucovsky_rayner_kang_appel_johnson_zhang_sayers_ade_whitten_2001, title={Electronic structure of noncrystalline transition metal silicate and aluminate alloys}, volume={79}, ISSN={["0003-6951"]}, DOI={10.1063/1.1404997}, abstractNote={A localized molecular orbital description ~LMO! for the electronic states of transition metal ~TM! noncrystalline silicate and aluminate alloys establishes that the lowest conduction band states are derived from d states of TM atoms. The relative energies of these states are in agreement with the LMO approach, and have been measured by x-ray absorption spectroscopy for ZrO2 ‐ SiO2 alloys, and deduced from an interpretation of capacitance‐voltage and current‐voltage data for capacitors with Al2O3 ‐T a 2O5 alloy dielectrics. The LMO model yields a scaling relationship for band offset energies providing a guideline for selection of gate dielectrics for advanced Si devices. © 2001 American Institute of Physics. @DOI: 10.1063/1.1404997# Noncrystalline alloys of group IIIB, IVB, and VB transition metal ~TM! oxides with SiO 2 and Al 2 O 3 , have been proposed as alternative gate dielectrics for advanced Si devices. 1 Interest in these alloys derives from their high dielectric constants, k, relative to SiO2, as well as their good thermal stability. Higher values of k allow use of physically thicker films to obtain the same effective capacitance as in SiO2 devices, and thus provides potential for significantly reduced direct tunneling. However, decreases in tunneling are mitigated in part by lower conduction band offset energies that define the barrier between thec-Si substrate and the dielectric. 2 This letter identifies a relationship between conduction band offset energies with respect to c-Si, 2,3 and the energy difference between the TM atomic n11 s and nd states providing a useful guideline for selection of alternative gate dielectrics. The calculations in Ref. 2 demonstrated that the lowest conduction bands in crystalline TM oxides are derived from atomic d states of TM atoms. The experimental results of Ref. 3 and this letter, and the localized molecular orbital ~LMO! model results presented below show that this assignment is not restricted to crystalline oxides, but applies more generally to noncrystalline TM oxides as well. In the LMO model, orbital energies of the lowest antibonding TM d states are determined predominantly by the coordination and symmetry of the TM atom, and are at energies approximately equal to the normalized TM atom d states. 4,5 Figure 1 displays x-ray absorption spectra ~XAS! for a series of Zr silicate alloys, (ZrO 2) x(SiO2) 12x , as obtained at beam line U4B at the National Synchrotron Light Source. Based on dipole selection rules, spectral features are assigned to transitions between M 2,3 p-core states of the Zr atoms, and conduction band states derived from 4d ~a and b, and a8 and b8! and 5s ~c and c8! Zr atomic states. The local bonding of Zr and Si atoms in these alloys has been addressed in Refs. 6 and 7. Plasma-deposited films prepared at 300 °C are noncrystalline alloys with Si‐O and Zr‐O bonds, but no detectable Zr‐Si bonds. 8 After annealing at 1000 °C, the x50.5 alloy separates into amorphous SiO2 and crystalline ZrO2, and the x51.0 end member, ZrO2, also crystallizes. The energies of features highlighted in the XAS spectra of Fig. 1 are independent of alloy composition and crystallinity to within an experimental uncertainty of 60.1 eV. Figure 2 is a schematic energy level diagram for a group IV TM atom bonded octahedrally to six O atoms. The top of the valence band is derived from nonbonding p orbitals of O 2p states. The lowest conduction bands are associated with TM nd states with t 2g (p*) and e g (s*) symmetries. The next conduction band with a1g(s*) symmetry is derived from TM n11 s states. Three distinct conduction bands have been previously reported in XAS studies of crystalline TiO2, 8 and TiS2 ~Ref. 9! in which the Ti atoms are octahedrally}, number={12}, journal={APPLIED PHYSICS LETTERS}, author={Lucovsky, G and Rayner, GB and Kang, D and Appel, G and Johnson, RS and Zhang, Y and Sayers, DE and Ade, H and Whitten, JL}, year={2001}, month={Sep}, pages={1775–1777} }
 @article{ryan_zhang_hesterberg_chou_sayers_2001, title={Formation of chloropyromorphite in a lead-contaminated soil amended with hydroxyapatite}, volume={35}, ISSN={["0013-936X"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-0035884175&partnerID=MN8TOARS}, DOI={10.1021/es010634l}, abstractNote={Conversion of soil Pb to pyromorphite [Pb5(PO4)3Cl] was evaluated by reacting a Pb contaminated soil collected adjacent to a historical smelter with hydroxyapatite [Ca5(PO4)3OH]. In a dialysis experiment where the soil and hydroxyapatite solids were placed in separate dialysis bags suspended in 0.01 M NaNO3 solution a crystalline precipitate, identified as chloropyromorphite, formed on the dialysis membrane containing the soil. The aqueous composition of the solution indicated that dissolution of solid-phase soil Pb was the rate-limiting step for pyromorphite formation. Addition of hydroxyapatite to the soil caused a decrease in each of the first four fractions of sequential extractable Pb and a 35% increase in the recalcitrant extraction residue. After a 240-d incubation at field-moisture content there was a further increase in the recalcitrant extraction residue fraction of the hydroxyapatite-amended soil to 45% of the total soil Pb. The increase in the extraction residue fraction in the hydroxyapatite amended 0-d incubated soil as compared to the control soil illustrates that the chemical extraction procedure itself caused changes in extractability. Thus, the chemical extraction procedure cannot easily be utilized to confirm changes occurring in amended soils. The further increase after the 240-d incubation implies that the reaction also occurs in the soil during incubation. Extended X-ray absorption fine structure (EXAFS) spectroscopy indicated that after the 240-d incubation the hydroxyapatite treatment caused a change in the average, local molecular bonding environment of soil Pb. Low-temperature EXAFS spectra (chi data and radial structure functions--RSFs) showed a high degree of similarity between the chemical extraction residue and synthetic pyromorphite, providing additional evidence that the change of soil Pb to pyromorphite is possible by simple amendments of hydroxyapatite to soil.}, number={18}, journal={ENVIRONMENTAL SCIENCE & TECHNOLOGY}, author={Ryan, JA and Zhang, PC and Hesterberg, D and Chou, J and Sayers, DE}, year={2001}, month={Sep}, pages={3798–3803} }
 @article{platow_wood_tracy_burnette_nemanich_sayers_2001, title={Formation of cobalt disilicide films on (root 3 x root 3)6H-SiC(0001)}, volume={63}, ISSN={["1550-235X"]}, DOI={10.1103/physrevb.63.115312}, abstractNote={This paper presents a detailed study of thin Co films grown directly, sequentially, and by codeposition with Si on the $(\sqrt{3}\ifmmode\times\else\texttimes\fi{}\sqrt{3})\ensuremath{-}R30\ifmmode^\circ\else\textdegree\fi{}$ surface of $6H\ensuremath{-}\mathrm{SiC}(0001).$ The structure, chemistry, and morphology of the films were determined using x-ray absorption fine structure, x-ray photoelectron spectroscopy, Auger electron spectroscopy, and atomic force microscopy. For directly deposited Co films (1--8 nm) graphite layers form on top of the film surface during annealing, whereas Co stays mainly unreacted over a temperature range of 300--1000 \ifmmode^\circ\else\textdegree\fi{}C. The formation of ${\mathrm{CoSi}}_{2}$ is achieved by sequential and codeposition of Co and Si. Films annealed at 550 \ifmmode^\circ\else\textdegree\fi{}C are polycrystalline and further annealing to 650 \ifmmode^\circ\else\textdegree\fi{}C causes no C segregation, but there is islanding of the films. Attempts to improve film morphology and homogeneity including applying a template method and varying growth temperature are also reported.}, number={11}, journal={PHYSICAL REVIEW B}, author={Platow, W and Wood, DK and Tracy, KM and Burnette, JE and Nemanich, RJ and Sayers, DE}, year={2001}, month={Mar} }
 @article{platow_nemanich_sayers_hartman_davis_2001, title={Growth of epitaxial CoSi2 on 6H-SiC(0001)(Si)}, volume={90}, ISSN={["1089-7550"]}, DOI={10.1063/1.1412842}, abstractNote={Epitaxial growth of (111)-oriented CoSi2 has been achieved on a scratch-free 6H-SiC(0001)Si substrate. The surface was prepared using atmospheric hydrogen etching and ultrahigh vacuum Si cleaning. A high-quality CoSi2 thin film was obtained by a modified template method and co-deposition of Co and Si at 550 °C. The structure and morphology of the film is studied by means of reflection high electron energy diffraction, x-ray absorption fine structure, x-ray diffraction, and atomic force microscopy.}, number={12}, journal={JOURNAL OF APPLIED PHYSICS}, author={Platow, W and Nemanich, RJ and Sayers, DE and Hartman, JD and Davis, RF}, year={2001}, month={Dec}, pages={5924–5927} }
 @article{alcacio_hesterberg_chou_martin_beauchemin_sayers_2001, title={Molecular scale characteristics of Cu(II) bonding in goethite-humate complexes}, volume={65}, ISSN={["1872-9533"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-0035010875&partnerID=MN8TOARS}, DOI={10.1016/S0016-7037(01)00546-4}, abstractNote={—Interactions between oxide minerals and natural organic matter affect metal adsorption properties of mineral surfaces, but the mechanisms of metal bonding are not well understood. Extended X-ray absorption fine structure (EXAFS) spectroscopy analyses were performed on aqueous pastes containing Cu(II) and goethite (α-FeOOH) with humic acid adsorbed at 0, 14, 28, 57, 88, 216, and 236 g kg−1 goethite, and with aqueous suspensions of humic acid only. Analyses were conducted at the Cu K edge with 40 mmol Cu(II) kg−1 goethite or 2 mmol Cu(II) kg−1 suspension for the humic acid system. Samples were equilibrated at pH 5.6 in a 0.1 M NaNO3 background electrolyte. For all systems, analysis of EXAFS results suggests that Cu(II) is present in a distorted octahedral configuration containing four short equatorial (1.94–1.97 Å) and two longer axial bonds with oxygen. When the concentration of adsorbed humic acid on goethite was increased from 0 to 28 g kg−1, the axial Cu-O bond length decreased to 2.24 ± 0.03 Å, which was less than for individual humic acid (2.32 ± 0.02 Å) or goethite (2.29 ± 0.03 Å) samples. The apparent decrease in the axial Cu-O bond length was attributed to a decrease in the ligand field splitting energy. When humic acid ligands replace equatorial water molecules in the Cu(II) coordination sphere, a weaker ligand field strength occurs. For absorbed humic acid up to 88 g kg−1 goethite, second-shell iron neighbors were observed between 3.17 and 3.20 Å, suggesting that Cu(II) was bonded on average to both inorganic (goethite) and organic (humic acid) functional groups. In addition, derivative X-ray absorption near edge structure (XANES) spectra for Cu(II) on goethite–humate complexes (<88 g kg−1) were poorly fit by use of a linear combination of spectra for Cu(II) on goethite or humate alone. At humate concentrations between 216 and 236 g kg−1 goethite, second-shell iron neighbors could not be identified, and the Cu-Oaxial distance (2.32 ± 0.02 Å) and derivative XANES spectra strongly resembled that of Cu(II) adsorbed to humate only. Analysis of the XANES and EXAFS data suggested that Cu(II) was bonded on average to both inorganic and organic functional groups as a type A ternary complex at lower levels of adsorbed humate, and to organic groups as a type B complex at higher levels.}, number={9}, journal={GEOCHIMICA ET COSMOCHIMICA ACTA}, author={Alcacio, TE and Hesterberg, D and Chou, JW and Martin, JD and Beauchemin, S and Sayers, DE}, year={2001}, month={May}, pages={1355–1366} }
 @article{platow_wood_burnette_nemanich_sayers_2001, title={XAFS studies of the formation of cobalt silicide on (root 3 x root 3) SiC(0001)}, volume={8}, ISSN={["0909-0495"]}, DOI={10.1107/S0909049500017921}, abstractNote={Thin Co films (1-8 nm) were directly, sequentially, and co-deposited with Si (3.6-29.2 nm) on the (31/2 × 31/2)-R30° reconstruction of 6H-SiC(0001). The films were annealed over a temperature range of 823-1373K and investigated with XAFS, XPS, AES and AFM. After annealing up to 1373K directly deposited Co films do not transform entirely to cobalt disilicide and C segregation is observed on the surface of the films. On the other hand, sequentially and co-deposited films do form cobalt disilicide after annealing at 823K, but also show islanding after annealing at 923K.}, journal={JOURNAL OF SYNCHROTRON RADIATION}, author={Platow, W and Wood, DE and Burnette, JE and Nemanich, RJ and Sayers, DE}, year={2001}, month={Mar}, pages={475–477} }
 @article{pisano_johnston_chapman_geradts_iacocca_livasy_washburn_sayers_zhong_kiss_et al._2000, title={Human breast cancer specimens: Diffraction-enhance imaging with histologic correlation - Improved conspicuity of lesion detail compared with digital radiography}, volume={214}, ISSN={["0033-8419"]}, DOI={10.1148/radiology.214.3.r00mr26895}, abstractNote={Seven breast cancer specimens were examined with diffraction-enhanced imaging at 18 keV with a silicon crystal with use of the silicon 333 reflection in Bragg mode. Images were compared with digital radiographs of the specimen, and regions of increased detail were identified. Six of the seven cases (86%) showed enhanced visibility of surface spiculation that correlated with histopathologic information, including extension of tumor into surrounding tissue.}, number={3}, journal={RADIOLOGY}, author={Pisano, ED and Johnston, RE and Chapman, D and Geradts, J and Iacocca, MV and Livasy, CA and Washburn, DB and Sayers, DE and Zhong, Z and Kiss, MZ and et al.}, year={2000}, month={Mar}, pages={895–901} }
 @article{zhong_thomlinson_chapman_sayers_2000, title={Implementation of diffraction-enhanced imaging experiments: at the NSLS and APS}, volume={450}, ISSN={["1872-9576"]}, DOI={10.1016/S0168-9002(00)00308-9}, abstractNote={Diffraction-enhanced imaging is a recently developed X-ray imaging technique that has demonstrated enhanced contrast for dense, highly absorbing materials of interest in materials science and medicine. The implementation of this technique in experiments at the National Synchrotron Light Source and at the Advanced Photon Source is described in detail.}, number={2-3}, journal={NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS AND ASSOCIATED EQUIPMENT}, author={Zhong, Z and Thomlinson, W and Chapman, D and Sayers, D}, year={2000}, month={Aug}, pages={556–567} }
 @article{porto_boyanov_sayers_nemanich_1999, title={Cobalt suicide formation on 6H silicon carbide}, volume={6}, ISSN={["0909-0495"]}, DOI={10.1107/S0909049599001326}, abstractNote={Cobalt films (1, 25 and 100 A) have been directly deposited on top 6H-SiC(0001) wafers by molecular beam epitaxy and annealed at 500-800°C in UHV. The structure of the metal-semiconductor interface was investigated by XAFS. The results show that Co-Si bonds were preferentially formed in the 1 A Co films. In the 25 and 100 A Co films only Co-Co bonds were identified. The XRD pattern of the 100 A Co film exhibits a Co (200) peak confirming the presence of unreacted metal even after annealing at 800°C.}, journal={JOURNAL OF SYNCHROTRON RADIATION}, author={Porto, AO and Boyanov, BI and Sayers, DE and Nemanich, RJ}, year={1999}, month={May}, pages={188–189} }
 @article{newville_boyanov_sayers_1999, title={Estimation of uncertainties in XAFS data}, volume={6}, ISSN={["0909-0495"]}, DOI={10.1107/S0909049598018147}, journal={JOURNAL OF SYNCHROTRON RADIATION}, author={Newville, M and Boyanov, BI and Sayers, DE}, year={1999}, month={May}, pages={264–265} }
 @article{goeller_boyanov_sayers_nemanich_myers_steel_1999, title={Germanium segregation in the Co/SiGe/Si(001) thin film system}, volume={14}, ISSN={["0884-2914"]}, DOI={10.1557/JMR.1999.0592}, abstractNote={Cobalt disilicide contacts to silicon–germanium alloys were formed by direct deposition of pure cobalt metal onto silicon–germanium films on Si(001) substrates. Segregation of germanium was observed during the reaction of the cobalt with the silicon–germanium alloy. The nature of the Ge segregation was studied by transmission electron microscopy, energy dispersive spectroscopy, and x-ray diffraction. In the case of cobalt films deposited onto strained silicon–germanium films, the Ge segregation was discovered to be in the form of Ge-enriched Si_1− x Ge_ x regions found at the surface of the film surrounding CoSi and CoSi_2 grains. In the case of cobalt films deposited onto relaxed silicon–germanium films, the Ge segregation was dependent on formation of CoSi_2. In samples annealed below 800 °C, where CoSi was the dominant silicide phase, the Ge segregation was similar in form to the strained Si_1− x Ge_ x case. In samples annealed above 800 °C, where CoSi_2 was the dominant silicide phase, the Ge segregation was also in the form of tetrahedron-shaped, Ge-enriched, silicon–germanium precipitates, which formed at the substrate/silicon– germanium film interface and grew into the Si substrate. A possible mechanism for the formation of these precipitates is presented based on vacancy generation during the silicidation reaction coupled with an increased driving force for Ge diffusion due to silicon depletion in the alloy layer.}, number={11}, journal={JOURNAL OF MATERIALS RESEARCH}, author={Goeller, PT and Boyanov, BI and Sayers, DE and Nemanich, RJ and Myers, AF and Steel, EB}, year={1999}, month={Nov}, pages={4372–4384} }
 @article{boyanov_goeller_sayers_nemanich_1999, title={Growth of epitaxial CoSi2 on SiGe(001)}, volume={86}, ISSN={["0021-8979"]}, DOI={10.1063/1.370894}, abstractNote={A technique for achieving epitaxial growth of (001)-oriented CoSi2 on strained epitaxial layers of Si1−xGex(001) is described. The technique is based on a variation of the template method, and is designed to control the local environment of Co atoms at the CoSi2/SiGe interface. The effects of the Co–Ge interactions on the interfacial reaction and the epitaxial orientation and the morphology of the silicide film were investigated. This reaction was found to cause pitting in (001)-oriented CoSi2 films, and to stabilize the (221¯) orientation for films codeposited under conditions where CoSi2(001) growth is achieved on Si(001) substrates. The (221¯)-oriented CoSi2 films were islanded after annealing at 700 °C. The islands were terminated by (1¯11) and (110) facets inclined at 15.8° and 19.5°, respectively, from CoSi2 [221¯] towards CoSi2 [114]. These results were interpreted in terms of reduction of interfacial and surface energies, and geometric effects. Silicide films up to 730-A-thick were deposited and a...}, number={3}, journal={JOURNAL OF APPLIED PHYSICS}, author={Boyanov, BI and Goeller, PT and Sayers, DE and Nemanich, RJ}, year={1999}, month={Aug}, pages={1355–1362} }
 @article{zhou_hesterberg_hansen_hutchison_sayers_1999, title={Stability of copper sulfide in a contaminated soil}, volume={6}, ISSN={["0909-0495"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-0033417334&partnerID=MN8TOARS}, DOI={10.1107/S0909049599001776}, abstractNote={Because of their low solubility under reduced soil conditions, metal sulfides may decrease the toxicity of heavy-metal contaminants. Periodic variations in soil moisture may expose reduced soils to oxidizing conditions that are conducive to oxidative dissolution of metal sulfides. Using EXAFS spectroscopy, we determined the proportion of copper sulfide in soil samples before and after exposure to more oxidizing conditions for 35 days at pH 6.6 or 7.6. The samples were collected from the reduced zone (47 to 73 and 73 to 101 cm depth) of a contaminated soil and contained about 1,700 mg Cu/kg. In both the original and the treated soil samples, we detected only Cu-S bonding in the first shell, indicating that the soil samples were not oxidized to Cu-O bonding during the treatment.}, number={1999 May 1}, journal={JOURNAL OF SYNCHROTRON RADIATION}, author={Zhou, WQ and Hesterberg, D and Hansen, PD and Hutchison, KJ and Sayers, DE}, year={1999}, month={May}, pages={630–632} }
 @article{boyanov_goeller_sayers_nemanich_1999, title={The effect of germanium on the Co-SiGe thin-film reaction}, volume={6}, ISSN={["0909-0495"]}, DOI={10.1107/S0909049599000060}, abstractNote={Ge Co Germanium was found to have a strong influence on the path and products of the Co-SiGe reaction, and on the interfacial stability and crystallographic orientation of the silicide film. The segregation of Ge that occurs during the reaction of blanket Co films with SiGe results in thickness effects not present in the reaction of Co with Si. The thickness effect was modelled in terms of the energy cost of Ge segregation, and good agreement with experimental results was obtained. In s i tu EXAFS experiments on sub-monolayer Co films annealed on SiGe substrates indicate a strong preference for the formation of Co-Si bonds at the silicide-SiGe interface. The implications of these results for the stability of the interface and the epitaxial orientation of co-deposited cobalt disilicide (CoSi2) films will be discussed.}, journal={JOURNAL OF SYNCHROTRON RADIATION}, author={Boyanov, BI and Goeller, PT and Sayers, DE and Nemanich, RJ}, year={1999}, month={May}, pages={521–523} }
 @article{hesterberg_zhou_hutchison_beauchemin_sayers_1999, title={XAFS study of adsorbed and mineral forms of phosphate}, volume={6}, ISSN={["0909-0495"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-0033438322&partnerID=MN8TOARS}, DOI={10.1107/S0909049599000370}, abstractNote={The solubility of inorganic phosphorus in soils is regulated by surface-adsorbed phosphate or phosphate minerals. The objective of this study was to determine whether different phosphate species of relevance to soils showed distinguishing XAFS spectral features. Phosphorus KXANES spectra for Fe-phosphates were characterized by a unique pre-edge feature near -3 eV (relative energy) that increased in intensity with increasing mineral crystallinity and was very weak for phosphate adsorbed on goethite. Spectra of Ca-phosphates and a soil sample exhibited a distinct shoulder on the high-energy side of the absorption edge. Spectra of Al-phosphates were characterized by a weak pre-edge feature at -1 eV.}, number={1999 May 1}, journal={JOURNAL OF SYNCHROTRON RADIATION}, author={Hesterberg, D and Zhou, WQ and Hutchison, KJ and Beauchemin, S and Sayers, DE}, year={1999}, month={May}, pages={636–638} }
 @article{goeller_boyanov_sayers_nemanich_1998, title={Co-deposition of cobalt disilicide on silicon-germanium thin films}, volume={320}, ISSN={["0040-6090"]}, DOI={10.1016/S0040-6090(97)00941-3}, abstractNote={The formation of CoSi2 on strained epitaxial Si0.8Ge0.2/Si(100) films has been studied as a function of the deposition method and annealing temperature. Two types of deposition processes were used: a direct method, where 5 nm of pure Co metal were deposited at room temperature onto a strained 80 nm thick Si0.8Ge0.2 layer; and a co-deposition method, where 5 nm Co and 18.2 nm Si were simultaneously deposited in a 1:2 ratio onto a strained Si0.8Ge0.2 layer at 450°C. Samples were then annealed at temperatures ranging from 500 to 800°C. Extended X-ray absorbance fine structure spectroscopy (EXAFS) and X-ray diffraction (XRD) were used to characterize the structure of the resulting films. It was found that the samples prepared via the direct deposition method did not convert to CoSi2 at any annealing temperature up to 800°C, while the co-deposited samples formed epitaxial CoSi2 at even the lowest annealing temperature of 500°C. These results are discussed in terms of proposed reaction mechanisms of the different deposition methods, based on consideration of the Co–Si–Ge ternary phase diagram.}, number={2}, journal={THIN SOLID FILMS}, author={Goeller, PT and Boyanov, BI and Sayers, DE and Nemanich, RJ}, year={1998}, month={May}, pages={206–210} }
 @article{boyanov_goeller_sayers_nemanich_1998, title={Film thickness effects in the Co-Si1-xGex solid phase reaction}, volume={84}, ISSN={["0021-8979"]}, DOI={10.1063/1.368872}, abstractNote={The thickness dependence of the reaction of cobalt with epitaxial silicon{endash}germanium alloys (Si{sub 1{minus}x}Ge{sub x}) has been studied. The reaction products of Co with (100)-oriented Si{sub 0.79}Ge{sub 0.21} after annealing at 800thinsp{degree}C depended on the thickness of the Co film. Complete conversion to CoSi{sub 2} occurred only when the thickness of the Co layer exceeded 350 {Angstrom}. Interface reactions with Co layers thinner than 50 {Angstrom} resulted in CoSi formation, while a mixture of CoSi and CoSi{sub 2} was formed at intermediate thicknesses. X-ray diffraction and extended x-ray absorption fine structure measurements indicated no measurable incorporation of Ge had occurred in either the CoSi or CoSi{sub 2}. The threshold thickness for nucleation of CoSi{sub 2} on (100)-oriented Si{sub 1{minus}x}Ge{sub x} was determined in the range 0{le}x{le}0.25. The threshold thickness increased superlinearly with the Ge concentration {ital x}, and did not depend on the doping of the Si(100) substrate or the strain state of the Si{sub 1{minus}x}Ge{sub x} film. The observed thickness effect was attributed to preferential Co{endash}Si bonding in the reaction zone and the energy cost of Ge segregation, which accompanies the formation of CoSi and CoSi{sub 2} during the reaction of Co with Si{sub 1{minus}x}Ge{sub x}. {copyright} {ital 1998more » American Institute of Physics.}« less}, number={8}, journal={JOURNAL OF APPLIED PHYSICS}, author={Boyanov, BI and Goeller, PT and Sayers, DE and Nemanich, RJ}, year={1998}, month={Oct}, pages={4285–4291} }
 @article{sayers_goeller_boyanov_nemanich_1998, title={In situ studies of metal-semiconductor interactions with synchrotron radiation}, volume={5}, ISSN={["0909-0495"]}, DOI={10.1107/S0909049597015240}, abstractNote={The capabilities and performance of a UHV system for in situ studies of metal-semiconductor interactions are described. The UHV system consists of interconnected deposition and analysis chambers, each of which is capable of maintaining a base pressure of approximately 1 x 10(-10) torr. The deposited materials and their reaction products can be studied in situ with RHEED, XAFS, AES, XPS, UPS and ARUPS. Results from a study of the reaction of 0.7- and 1.7-monolayer-thick films of cobalt with strained silicon-germanium alloys are presented. The signal-to-noise ratio obtained in these experiments indicates that the apparatus is capable of supporting in situ EXAFS studies of approximately 0.1-monolayer-thick films.}, journal={JOURNAL OF SYNCHROTRON RADIATION}, author={Sayers, DE and Goeller, PT and Boyanov, BI and Nemanich, RJ}, year={1998}, month={May}, pages={1050–1051} }
 @article{wang_goeller_boyanov_sayers_nemanich_1997, title={An integrated growth and analysis system for in-situ XAS studies of metal-semiconductor interactions}, volume={7}, ISSN={["1155-4339"]}, DOI={10.1051/jp4/1997096}, abstractNote={A UHV system for in-situ studies of metal-semiconductor interactions has been designed and assembled at North Carolina State University and recently installed and tested at the NSLS. The UHV system consists of interconnected deposition and analysis chambers, each of which is capable of maintaining a base pressure of approximately 1 x 10 -10 Torr. Up to three materials can be co-deposited on 25 mm wafers by electron-beam evaporation. Substrate temperature can be controlled in the range 30-900 °C during deposition, and the growth process may be monitored with RHEED. The deposited materials and their reaction products can be studied in-Situ with a variety of technique: XAFS, AES, XPS, UPS and ARXPS/UPS. We describe the capabilities of the system and present our first EXAFS results on the stabilization of Co + 2 Si films co-deposited on Si 0.8 Ge 0.2 alloys. Preliminary results indicate that Co + 2Si forms a stable film on Si 0.8 Ge 0.2 with a CoSi 2 -like reaction path. As is the case with CO/Si 0.8 Ge 0.2 , silicide formation is complete at 700 °C. However, the Co+2Si/Si 0.8 Ge 0.2 system does not undergo a Cosi → CoSi 2 transition when annealed at 500-700 °C, and exhibits only weak CoSi features in this temperature range.}, number={C2}, journal={JOURNAL DE PHYSIQUE IV}, author={Wang, Z and Goeller, PT and Boyanov, BI and Sayers, DE and Nemanich, RJ}, year={1997}, month={Apr}, pages={561–564} }
 @article{pandya_anderson_sayers_ogrady_1997, title={Characterization of carbon supported Pt/Ru alloy particles using EXAFS spectroscopy}, volume={7}, ISSN={["1155-4339"]}, DOI={10.1051/jp4:1997299}, abstractNote={mu alloys are used for electmoxidation of methanol in direct methanol he1 cells. Theii catalytic activity shun& depends upon the stmckm and +tim of the We have investigated the stmhre of PtlRu alloy particles #anhighsurface~csrtmhthreedifferent compositions, namely Pt:Ru,8.5:1.5.1:1 and 1.5:8.5. The samples were prepared by impregnating the carbon with salt solutions ofthe two metals fdlowed by redwAon to the alloy. The total metal hdiag was I0 wt%. The Pt L, andRuKEXAFS -ts were e'. Data Processing: The EXAFS function ~(k) was separated from the experimentally measured absorption specbum using the standard procedures. The R L, and Ru Kedge radial shwture functions (RSFs) for the alloy samples are shown in the figures 3 and 4, respectively. The RSFs are sigdkdy different from each other indicating that the structure strongly depends upon the composition. The effect of the}, number={C2}, journal={JOURNAL DE PHYSIQUE IV}, author={Pandya, KI and Anderson, EB and Sayers, DE and OGrady, WE}, year={1997}, month={Apr}, pages={955–956} }
 @article{bazin_sayers_rehr_1997, title={Comparison between X ray absorption spectroscopy, anomalous wide angle X ray scattering, anomalous small angle X ray scattering, and diffraction anom}, volume={101}, number={51}, journal={Journal of Physical Chemistry. B, Condensed Matter, Materials, Surfaces, Interfaces & Biophysical}, author={Bazin, D. C. and Sayers, D. A. and Rehr, J. J.}, year={1997}, pages={11040–11050} }
 @article{chapman_thomlinson_johnston_washburn_pisano_gmur_zhong_menk_arfelli_sayers_1997, title={Diffraction enhanced X-ray imaging}, volume={42}, number={11}, journal={Physics in Medicine & Biology}, author={Chapman, D. and Thomlinson, W. and Johnston, R. E. and Washburn, D. and Pisano, E. and Gmur, N. and Zhong, Z. and Menk, R. and Arfelli, F. and Sayers, D. E.}, year={1997}, pages={2015–2025} }
 @article{wang_aldrich_nemanich_sayers_1997, title={Electrical and structural properties of zirconium germanosilicide formed by a bilayer solid state reaction of Zr with strained Si1-xGex alloys}, volume={82}, ISSN={["0021-8979"]}, DOI={10.1063/1.366043}, abstractNote={The effects of alloy composition on the electrical and structural properties of zirconium germanosilicide (Zr–Si–Ge) films formed during the Zr/Si1−xGex solid state reaction were investigated. Thin films of Zr(Si1−yGey) and C49 Zr(Si1−yGey)2 were formed from the solid phase reaction of Zr and Si1−xGex bilayer structures. The thicknesses of the Zr and Si1−xGex layers were 100 and 500 A, respectively. It was observed that Zr reacts uniformly with the Si1−xGex alloy and that C49 Zr(Si1−yGey)2 with y=x is the final phase of the Zr/Si1−xGex solid phase reaction for all compositions examined. The sheet resistance of the Zr(Si1−yGey)2 thin films was higher than the sheet resistance of similarly prepared ZrSi2 films. The stability of Zr(Si1−yGey)2 in contact with Si1−xGex was investigated and compared to the stability of Ti(Si1−yGey)2 in contact with Si1−xGex. The Ti(Si1−yGey)2/Si1−xGex structure is unstable when annealed for 10 min at 700 °C, with Ge segregating from Ti(Si1−yGey)2 and forming Ge-rich Si1−zGez pr...}, number={5}, journal={JOURNAL OF APPLIED PHYSICS}, author={Wang, Z and Aldrich, DB and Nemanich, RJ and Sayers, DE}, year={1997}, month={Sep}, pages={2342–2348} }
 @inproceedings{wang_hesterberg_zhou_sayers_robarge_1997, title={Extended x-ray absorption fine structure study of mercury speciation in a flood plain soil}, number={1997}, booktitle={Contaminated soils: 3rd International Conference on the Biogeochemistry of Trace Elements, Paris (France), May 15-19, 1995}, publisher={Paris: INRA Editions}, author={Wang, Z. and Hesterberg, D. and Zhou, W. and Sayers, D. E. and Robarge, W. P.}, year={1997} }
 @article{reifsnyder_otten_sayers_lamb_1997, title={Hydrogen chemisorption on silica-supported Pt clusters: In situ X-ray absorption spectroscopy}, volume={101}, ISSN={["1089-5647"]}, DOI={10.1021/jp970244e}, abstractNote={Hydrogen chemisorption on small silica-supported Pt clusters was investigated using in situ extended X-ray absorption fine structure (EXAFS) spectroscopy and X-ray absorption near-edge structure (XANES) spectroscopy. The clusters were found to exhibit a bulklike Pt first nearest neighbor (NN) distance (2.76 A) and low disorder while covered by chemisorbed hydrogen. In contrast, bare Pt clusters produced by heating in vacuo at 300 °C are characterized by a contracted Pt NN distance (2.66 A) and greater disorder. These effects are reversed by re-exposure of the bare Pt clusters to H2 at 25 °C. The metal−support interface is characterized by a short Pt−O distance, irrespective of the presence of chemisorbed hydrogen. An apparent L3 edge shift of 0.8 eV relative to bulk Pt is observed for the hydrogen-covered clusters. This shift is attributed to a decrease in the Pt L3 edge resonance (white line) intensity, as no corresponding shift is observed at the L2 edge. A hydrogen-related L2,3 XANES feature at 9 eV ap...}, number={25}, journal={JOURNAL OF PHYSICAL CHEMISTRY B}, author={Reifsnyder, SN and Otten, MM and Sayers, DE and Lamb, HH}, year={1997}, month={Jun}, pages={4972–4977} }
 @article{bazin_sayers_rehr_mottet_1997, title={Numerical simulation of the platinum L (III) edge white line relative to nanometer scale clusters}, volume={101}, number={27}, journal={Journal of Physical Chemistry. B, Condensed Matter, Materials, Surfaces, Interfaces & Biophysical}, author={Bazin, D. and Sayers, D. E. and Rehr, J. J. and Mottet, C.}, year={1997}, pages={5332–5336} }
 @article{boyanov_goeller_sayers_nemanich_1997, title={Preferential Co-SI bonding at the Co/SiGe(100) interface}, volume={71}, DOI={10.1063/1.119436}, abstractNote={The initial stages of the reaction of Co with Si0.79Ge0.21(100) were studied in situ with extended x-ray absorption fine structure spectroscopy and reflection high energy electron diffraction. The Si:Ge ratio in the first coordination shell of Co in sub-monolayer Co films was found to increase with film thickness and annealing temperature, indicating preferential formation of Co–Si bonds. The impact of the observed preference for Co–Si bonding on the morphology of epitaxial CoSi2/Si1−xGex heterostructures is discussed.}, number={21}, journal={Applied Physics Letters}, author={Boyanov, B. I. and Goeller, P. T. and Sayers, D. E. and Nemanich, R. J.}, year={1997}, pages={3060–3062} }
 @article{goeller_boyanov_sayers_nemanich_1997, title={Structure and stability of cobalt-silicon-germanium thin films}, volume={133}, ISSN={["0168-583X"]}, DOI={10.1016/S0168-583X(97)00458-8}, abstractNote={The phase formation and stability of CoSi2 on strained epitaxial Si0.80Ge0.20Si (0 0 1) thin films has been investigated. Silicide films prepared via direct deposition of cobalt (CoSiGe), and via co-deposition of silicon and cobalt (Co+2SiSiGe), were compared. EXAFS, XRD, and sheet-resistance measurements indicated that co-deposited Co+2Si films annealed at 400–700°C exhibit the expected low-resistivity CoSi2 structure but were susceptible to roughening, pinhole formation, and agglomeration. In contrast, the CoSiGe structure formed CoSi2 only after annealing at 700°C and silicide formation was accompanied by Ge segregation in the contact region. In situ RHEED experiments indicated that growth of CoSi2 co-deposited on SiGe at 400–500°C results in immediate island formation. Template methods, which are often used to enhance the quality of co-deposited Co+2SiSi structures, did not lead to two-dimensional growth in the Co+2SiSiGe system. In situ EXAFS measurements of 2 Å Co films deposited on SiGe substrates and annealed at 450°C suggested that the failure to achieve two-dimensional growth may be due to preferential bonding of Co to Si atoms at the interface, which prevents the formation of a continuous CoSi2 template.}, number={1-4}, journal={NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION B-BEAM INTERACTIONS WITH MATERIALS AND ATOMS}, author={Goeller, PT and Boyanov, BI and Sayers, DE and Nemanich, RJ}, year={1997}, month={Dec}, pages={84–89} }
 @article{hesterberg_sayers_zhou_plummer_robarge_1997, title={X-ray absorption spectroscopy of lead and zinc speciation in a contaminated groundwater aquifer}, volume={31}, ISSN={["1520-5851"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-0031260138&partnerID=MN8TOARS}, DOI={10.1021/es970077w}, abstractNote={The formation of insoluble metal sulfides in the environment may reduce the mobility and bioavailability of heavy metal contaminants and potentially eliminate the need for ex situ remediation of certain hazardous waste sites. To assist in assessing remediation strategies for the Bypass 601 Superfund site, groundwater aquifer samples were analyzed using synchrotron X-ray absorption spectroscopy (XAS) to determine whether lead and zinc sulfides were dominant mineral phases. Moist aquifer solids contained between 150 and 1800 mg of Pb/kg and between 100 and 250 mg of Zn/kg. Lead sulfide was not dominant in any of the samples analyzed, including one sample collected from a well in a flood plain that contained 70% of zinc bonded to sulfur, probably as ZnS. This portion of the aquifer had apparently been under reducing conditions. In all other samples, first-shell bonding of Pb and Zn was predominantly to oxygen. Data indicated that PbO, PbCO3, PbSO4, and ZnO were not dominant metal species. The XAS analyses sh...}, number={10}, journal={ENVIRONMENTAL SCIENCE & TECHNOLOGY}, author={Hesterberg, D and Sayers, DE and Zhou, WQ and Plummer, GM and Robarge, WP}, year={1997}, month={Oct}, pages={2840–2846} }
 @article{hesterberg_sayers_zhou_robarge_plummer_1997, title={XAFS Characterization of Copper in Model Aqueous Systems of Humic Acid and Illite}, volume={7}, ISSN={1155-4339}, url={http://dx.doi.org/10.1051/jp4:1997253}, DOI={10.1051/jp4:1997253}, abstractNote={Adsorption of heavy metals at mineral surfaces and complexation with reactive organic-matter functional groups are important processes regulating the solubility and fate of soil contaminants. To determine the nature of Cu(II) bonding in complex clay-organic systems, XAFS analyses were conducted on aqueous suspensions containing Cu(II) in various forms: (i) complexed with soil humic acid (HA) at various HA:Cu ratios, (ii) bound to illite, or (iii) bound in a mixture of illite and HA. Spectral features for Cu bound to HA did not depend significantly on the HA:Cu ratio, and average first-shell Cu-O bond lengths were consistently shorter than for the Cu-illite systems. In the mixed clay-organic suspension, Cu bonding was more characteristic to that of Cu bound with HA.}, number={C2}, journal={Le Journal de Physique IV}, publisher={EDP Sciences}, author={Hesterberg, D. and Sayers, D. E. and Zhou, W. and Robarge, W. P. and Plummer, G. M.}, year={1997}, month={Apr}, pages={C2–833-C2–834} }
 @article{sayers_hesterberg_zhou_robarge_plummer_1997, title={XAFS characterization of copper contamination in the unsaturated and saturated zones of a soil profile}, volume={7}, ISSN={["1155-4339"]}, DOI={10.1051/jp4:1997252}, abstractNote={The fate of heavy-metal contaminants in the environment, and the design and success of remediation strategies at hazardous waste sites depend on the chemical speciation of the contaminants. The objective of this study was to determine the molecular-scale chemical form (species) of heavy metals in different zones of a contaminated soil having a shallow ground water table. Copper in the unsaturated surface horizon and the water-saturated and partially-saturated subsurface horizons of a disturbed soil from the lower eastern coastal plain of North Carolina was characterized using XAFS spectroscopy. Extended x-ray absorption fine structure (EXAFS) and x-ray absorption near edge structure (XANES) data showed that the dominant form of Cu(II) bonding ranged from Cu-S in the deeper soil zones to Cu-O in the shallowest zone. The results suggest that the surface and subsurface horizons will respond differently to remediation treatments.}, number={C2}, journal={JOURNAL DE PHYSIQUE IV}, author={Sayers, DE and Hesterberg, D and Zhou, W and Robarge, WP and Plummer, GM}, year={1997}, month={Apr}, pages={831–832} }