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We present results of X-ray fluorescence measurements (carbon Kα and Si L2,3) of methylhydroxylsiloxane and phenylmethylhydroxylsiloxane films. The films are converted into amorphous ceramics by irradiation with 500 keV C and 3 MeV Au ions. Changes in the composition (O/Si ratio) of some polysiloxane films are found when treated with ion irradiation. It is shown that ion irradiation induces a segregation of carbon atoms from methyl groups into diamond-like clusters whereas carbon atoms from phenyl groups maintain their sp2 configuration.

We have used ion-beam mixing to form Si nano-crystals in SiO2 and SiO2/Si multilayers, and applied photoluminescence and soft-X-ray emission spectroscopy to study the nanoparticles. Ion-beam mixing followed by heat treatment at 1100 °C for 2 h forms the Si nanocrystals. The ion-beam-mixed sample shows higher PL intensity than that of a Si-implanted SiO2 film. Photon and electron-excited Si L2,3 X-ray emission measurements were carried out to confirm the formation of Si nanocrystal in SiO2 matrix after ion-beam mixing and heat treatment. It is found that Si L2,3 X-ray emission spectra of ion-beam-mixed Si monolayers in heat-treated SiO2 films lead to noticeable changes in the spectroscopic fine structure.

Soft x-ray fluorescence spectroscopy has been used to examine the electronic structure of deeply buried silicide thin films that arise in Fe/Si multilayers. These systems exhibit antiferromagnetic (AF) coupling of the Fe layers, despite their lack of a noble metal spacer layer found in most GMR materials. Also, the degree of coupling is very dependent on preparation conditions, especially spacer layer thickness and growth temperature. The valence band spectra are quite different for films with different spacerlayer thickness yet are very similar for films grown at different growth temperatures. The latter result is surprising since AF coupling is strongly dependent on growth temperature. Combining near-edge x-ray absorption with the fluorescence data demonstrates that the local bonding structure in the silicide spacer layer in epitaxial films which exhibit AF coupling are metallic. These results indicate the equal roles of crystalline coherence and electronic structure in determining the magnetic properties of these systems.

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and L2 resonances, especially strong at the L3 resonance, while inelastic peaks were observed from well below the resonance and showed complex features at the excitation energies between the Ti L3 and L2 resonances. The measured spectra were explained based on radiative and non-radiative electronic processes near the Ti-L2,3 edge in the titanate.

Silicon L2,3 x-ray emission spectra (XES) of siloxene powder samples prepared according to Wöohler and Kautsky (Wöhler and Kautsky siloxene) are presented. The results are compared with the Si L2,3 spectra of the reference compounds a-Si, c-Si, SiO2, and SiOx. A close similarity of the electronic structure of Wöhler siloxene to that of a-SiO0.43: H and of Kautsky siloxene to that of a-SiO0.87: H is found. We determine the number of oxygen atoms per Si atom at ~0.5 in Wöhler siloxene and ~0.8 in Kautsky siloxene. The relative concentrations are in good agreement with the results of infrared absorption measurements on the same samples.

Soft x-ray fluorescence spectroscopy provides an element and angular momentum selective measure of the valence band density of states in complex materials. Results are presented demonstrating the use of SXF both as a means of solving materials problems and as a means of increasing our fundamental understanding of low energy excitation processes in various types of materials. As examples of materials applications, we discuss the L2,3 spectra of Si in various environments, and describe radiation damage studies in Beryl. Fundamental new insights are provided by the study of SXF spectra excited near an x-ray threshold. For such excitation, recent work demonstrates that an electronic Raman scattering process can greatly modify the normal fluorescence spectrum. We discuss near threshold studies of graphite, h-BN and NiS to demonstrate that the nature of the electronic excitation processes differs dramatically in various classes of materials and provides important new insights into their properties.

The full spectrum of occupied and unoccupied σ and Π orbitals is presented for solid C60, C70, and graphite, using C1s emission and absorption spectroscopy. There are significant differences between C60 and C70, and even larger changes relative to their infinite analog graphite C∞. A comparison is made with photoemission and inverse photoemission results, along with first principles quasiparticle calculations.

We are using resonant soft x-ray fluorescence at the Advanced Light Source to probe the electronic and geometric structure of novel materials. In the resonant process, a core electron is excited by a photon whose energy is near the core binding energy. In this energy regime the absorption and emission processes are coupled, and this coupling manifests itself in several ways. In boron nitride (BN), the resonant emission spectra reflect the influence of a “spectator” electron in an unoccupied excitonic state. The resonant emission can be used to distinguish between the various bulk phases of BN, and can also be used to probe the electronic structure of a monolayer of BN buried in a bulk environment, where it is inaccessible to electron spectroscopies. For highly-oriented pyrolytic graphite (HOPG) a coherent absorption-emission process takes place in the resonant regime, whereby crystalline momentum is conserved between the core excited electron and the valence hole which remains after emission

Monochromatized synchrotron radiation has been employed as the excitation source for soft x-ray emission spectroscopy. In the present paper changes in the emission spectra that occur as the excitation energy is varied near the core-absorption threshold are discussed. In the case of crystalline silicon, strong variations are seen in the L2,3 emission for excitation energies up to 30 eV above threshold. These variations are shown to be dependent on the crystalline order of the material and can be interpreted in terms of restrictions on the crystal momentum that arise in an inelastic scattering description of the combined absorption and emission. On the other hand this description is less relevant to the excitation-energy dependence of ionic insulators, in which strong phonon coupling removes these restrictions on crystal momentum. In the insulators B2O3 and BN strong variations in the emission are observed at threshold, upon creation of a core exciton: the exciton affects the emission through its influence on the phonon coupling as well as on the initial and final-state screening.