R. P. Winarski

Soft X-ray emission spectroscopy of early transition metal compounds

Abstract Soft X-ray emission studies for several early transition metal compounds, such as Sc, Ti and V compounds, have been studied. Raman scattering was found at the 2p→3d excitation in the transition metal compounds. The elementary excitation of the Raman spectrum is mainly elucidated by the d–d transition within the 3d bands, as well as the interband transition from the O 2p valence band to the conduction band, which consists mainly of transition metal 3d states. The charge transfer transition due to the localized electron picture is dominant in the soft X-ray spectra of Sc compounds. Raman scattering is a powerful tool in the study of the electronic structure of transition metal compounds.

Electronic structures of the tungsten borides WB, W2B and W2B5

Abstract The electronic structures of the tungsten borides WB, W 2 B and W 2 B 5 were studied experimentally and theoretically. Using monochromatic synchrotron radiation as the excitation source, soft X-ray emission and absorption spectroscopic techniques were employed to probe the occupied and unoccupied states of the valence band, respectively. The linear muffin-tin orbital method was used to calculate the ground state electronic properties of these compounds. The experimental spectroscopic data and the calculated angular momentum- and site-projected densities of states yielded new useful information regarding bonding and hybridization in these materials.

Mechanism for interfacial adhesion strength of an ion beam mixed Cu/polyimide with a thin buffer layer

A Cu (400 A)/Al (50 A)/polyimide system showed larger adhesion strength than that of Cu (400 A)/polyimide after N2+ ion beam mixing. X-ray emission spectroscopy was performed to elucidate the mechanism of adhesion enhancement of the ion beam mixed Cu (400 A)/polyimide with a thin Al buffer layer. Cu L2,3 x-ray emission spectra showed the formation of a CuAl2O4 layer which is strongly correlated with the large adhesion strength of a Cu/Al/polyimide. A decrease in adhesion strength at an ion dose higher than 5×1015 cm−2 was also explained by the formation of an amorphous carbon. This was understood by investigating C Kα x-ray emission spectra. The overall spectroscopic results were in accordance with the behavior of quantitative adhesion strength.

Soft X-ray fluorescence measurements of irradiated polymer films

Fluorescent soft X-ray carbon Ka emission spectra (XES) have been used to characterize the bonding of carbon atoms in polyimide (PI) and polycarbosilane (PCS) films. The PI films have been irradiated with 40 keV nitrogen or argon ions, at fluences ranging from 1 · 10 14 to 1 · 10 16 cm ˇ2 . The PCS films have been irradiated with 5 · 10 15 carbon ions cm ˇ2 of 500 keV and/or annealed at 1000∞C. We find that the fine structure of the carbon XES of the PI films changes with implanted ion fluence above 1 · 10 14 cm ˇ2 which we believe is due to the degradation of the PI into amorphous C:N:O. The width of the forbidden band as determined from the high-energy cut-oA of the C Ka X-ray excitation decreases with the ion fluence. The bonding configuration of free carbon precipitates embedded in amorphous SiC which are formed in PCS after irradiation with C ions or combined treatments (irradiation and subsequent annealing) is close to either to that in diamond-like films or in silicidated graphite, respectively. ” 1998 Elsevier Science B.V. All rights reserved.

Characterization of CNx-films by X-ray emission measurements

The local atomic bonding structure of carbon nitride films synthesized by the reactive ionized cluster beam method using X-ray emission spectra (XES) was examined. An ionized cluster beam system was used to prepare the carbon nitride films. The composition of carbon nitride films was measured with Rutherford backscattering spectroscopy techniques and the N/C ratio was found to be approximately 0.25. The XES measurements of the carbon nitride films showed a predominant proportion of sp bonded carbon and nitrogen atoms.

Chemical reactions in polymers induced by ion beam mixing: fluorescence X-ray measurements

Fluorescent soft X-ray emission spectroscopy (XES) is used to study chemical reactions in polyimide (PI), poly- ethersulphone (PES) and polycarbosilane (PCS) films induced by ion-beam mixing. It is found that the fine structure of the 14 22 carbon XES of the PI and PES films is modified after irradiation with fluences above 1310 cm , which is attributed to the degradation of the molecular structure in amorphous C:N:O. The width of the electronic gap decreases with the ion fluence, in correlation with reported increase of conductivity and optical absorption. The bonding configuration of free carbon precipitated in a matrix of a-SiC after irradiation of PCS is closer to that of diamond-like carbon than in a film submitted to combined treatments of irradiation1annealing or direct annealing. Nevertheless clusters formed in the annealed 2 PCS films are less sp -hybridized than in silicidated graphite or sputtered Si:C:H films.

Soft X-ray fluorescence measurements of polyimide films

Abstract Fluorescent X-ray emission spectroscopy has been used for the first time to study the electronic structure of polyimide films (PMDA-ODA) prepared on Si-substrates by spin-coating and ionized cluster beam deposition (ICBD) methods. The observed C K α and O K α X-ray emission spectra that probe the C 2 p and O 2 p partial density of states in the valence band, respectively, were compared with X-ray photoelectron valence band spectra. Theoretical simulations of X-ray energies and intensities for polyimide were performed with molecular orbital (MO) calculations of the model monomer, containing 41 atoms, utilizing a semi-empirical Hydrogenic Atoms in Molecules, V. 3 (HAM/3) method. Calculated Al K α photoelectron spectra were obtained using Gaussian lineshape functions of an approximate linewidth (0.10 I k for the model molecule): I k = I ′ k − WD , as indicated for analysis of valence X-ray photoelectron spectra for 63 polymers from some of our previous work. Theoretical C K α and O K α X-ray emission and valence X-ray photoelectron spectra show good agreement with the experimental results, and were used to identify certain spectral features.

Study of 4f inner shell excitations in Gd and Tb using resonant inelastic soft X-ray scattering

Abstract Inelastic scattering of 4d electrons near the 4d–4f threshold of Gd2O2S and Tb4O7 has been studied with monochromatic synchrotron radiation excitation. The emission in the vicinity of the 4d–4f threshold is dominated by inelastic and elastic scattering. The energy losses are due to 4f inner-shell excitations in which the d-electrons (initial state 4d104fn) are excited to the 4f level (intermediate state 4d94fn+1) and then refill the open d-shell (final state 4d104fn+1) leaving the 4f shell in an excited state. Our atomic calculations are in excellent agreement with the experimental emission spectra indicating strong localization of the 4f electrons.

Soft X-ray scattering dominates emission near the giant resonance of the rare earth compounds

Abstract Inelastic scattering of 4d electrons near the 4d–4f thresholds of Gd 2 O 2 S and Tm 2 O 3 is studied with monochromatic synchrotron radiation excitation. The emission is dominated by inelastic scattering. We observe two energy loss mechanisms, which are 4f inner-shell excitations (4d 10 4f n →4d 9 4f n +1 →4d 10 4f n ) and 5p–4f excitations (4d 10 5p 6 4f n →4d 9 5p 6 4f n +1 →4d 10 5p 5 4f n +1 ). Our atomic calculations are in excellent agreement with the experimental emission spectra indicating strong localization and a low degree of correlation of the 4f electrons. Inelastic scattering can be used to elucidate the relative partial cross sections for the contributing transitions.

X-ray emission study of ion beam mixed Cu/Al films on polyimide

Cu (40 nm)/Al/polyimide/Si was mixed with 80 keV Ar+ and N2+ from 5.0×1015 to 15×1015 ions/cm2. Ultrasoft x-ray emission valence spectra (XES) of Cu, C, N and O excited by electron and photon radiation were used for study of chemical reactions in Cu/Al/PI/Si and PI/Si systems induced by ion beam mixing in dependence of type of ions and dose. It is found that ion beam mixing changes the chemical state of Cu atoms with respect to that of pure metal. These changes depend on the dose of ion beam bombardment and type of ions and are attributed to a formation of CuAl2O4 interfacial layer, which can be responsible for enhanced interfacial adhesion strength. On the other hand, it is shown that the shape of C Kα, N Kα and O Kα XES of ion beam mixed polyimide layer (PI/Si) is modified with ion bombardment. This means that the ion-beam mixing process is able to break the bonding of constituent atoms of irradiated PI layers and can induce the formation of chemically bonded complexes linking atoms in the Cu, Al and PI...