Papers by Keyword: X-Ray Reflectivity

Abstract: In this article, we studied feasibility of growing Fe-Ni alloy thin films on both Si and glass substrates by using electron-gun deposition technique. Fe and Ni powders were mechanically alloyed with different percentages by ball mill technique. The final milled powder was used as a source material for depositing process. Powder materials were characterized structurally by using x-ray diffraction whereas grown thin films were analyzed by using x-ray reflectivity. The x-ray diffraction data of milled powder revealed a peak shift compared to the unmilled Ni and Fe peaks resulted in obtaining alloyed material. The distinct Kiessig fringes in the relative length scale are evidence of good layer quality in alloy thin films. The film grown on Si substrate exhibited more extended Kiessig fringes in reflectivity scans and the broadening of diffuse part in rocking curves scan became narrower as compared to the glass substrate; this indicated less interface roughness of the alloyed layer grown on silicon substrate. The chemical composition of the grown material was established through optical emission spectrometry. The results were much close to the percentage of prepared alloyed powder material.

Abstract: Epitaxial bilayer structure consisting of ferromagnetic (FM) metallic Pr_0.7Sr_0.3MnO₃ (PSMO) and antiferromagnetic (AFM) insulator La_0.5Ca_0.5MnO₃ (LCMO) was fabricated on (001)-oriented single crystal SrTiO₃ (STO) substrate by pulsed laser deposition technique. We studied the surface structure and interdiffusion at interface between PSMO and LCMO by using atomic force microscope and grazing incident x-ray reflectivity (GIXRR). The perfect data fitting result of GIXRR indicated that interdiffusion at the interface of Pr_0.7Sr_0.3MnO₃/La_0.5Ca_0.5MnO₃ (PSMO/LCMO) could not be negligible; there was a large interdiffusion zone at the PSMO/LCMO interfaces with a thickness of about 7 nm. We found that the thickness of the top layer at air/PSMO interface was about 2.5 nm and the mass density of the top layer was about 76.53% of that of PSMO layer. The surface roughness was about 1.6 nm which was consistent with observation by atomic force microscopy. Normal X-ray diffraction (NXRD) was also employed to investigate the average structure. Except from PSMO and LCMO layer diffraction peaks, we observed another additional peak, which was developed from the large disordered layer resulting from interdiffusion at the interface of PSMO/LCMO. This implied that the variation of crystalline structure of PSMO/LCMO film occurred due to interdiffusion. Surface roughness and interdiffusion played an important role in magnetic properties of FM/AFM bilayer.

Abstract: We present a study of the improvement in interface roughness of platinum/carbon multilayers for X-ray mirrors. The X-ray reflectivity of multilayers strongly depends on interface quality. In an effort to reduce the interface roughness caused by crystallization during deposition, carbon doping of platinum was proposed, and its effectiveness was evaluated. We compared 45-nm-thick single-layer platinum to carbon-doped platinum films. The films were deposited on a silicon (100) substrate by dc magnetron sputtering deposition. The surface roughness and X-ray diffraction spectrum of each film were measured by atomic force microscopy and X-ray diffraction, respectively. We concluded that the increase in carbon concentration suppresses the crystallization of platinum and causes the surface roughness to decrease.

Abstract: The structural origin of imprint in Pb(Zr,Ti)O₃ (PZT) ferroelectric thin films derived by chemical solution deposition with Pt top and bottom electrodes was studied by in-situ high-resolution X-ray specular reflectivity of synchrotron radiation. Global structural parameters of density, thickness, and surface or interface roughness of each component layer in the thin film sample were obtained. No generation of interfacial layers with a different electron density from PZT and no interface roughening were observed at the interfaces of PZT and Pt during imprint. Thus, the results suggest that the imprint effect is more likely a bulk or electronic defects-related phenomenon.

Abstract: Thin films of hydrogenated silicon-oxycarbide (a-SiOCx:H) have largely replaced pure silicon oxide films as back end of line (BEOL) processing in Ultra Large Scale Integrate Circuit (ULSI). A single chamber system for hot wire chemical vapor deposition (HWCVD) was employed to deposit different films of a-SiOCx:H with 0.5 < x < 0.8. All films were characterized by infrared spectroscopy and X-ray photoelectron spectroscopy (XPS) to determine the stoichiometry and the presence of various bonding configurations of constituent atoms. We used X-ray reflectivity (XRR) and Small angle X- ray scattering (SAXS) to determine the porosity and inhomogeneities (clustering) in the films.

Abstract: In the study, an interlayer was observed in a nano-meter scale SiO2 overlayer on Si substrate by X-ray reflectivity(XRR) analysis and a new method is introduced for the XRR analysis of SiO2 ultra-thin films on Si substrate. The normalized reflectivity curves were analyzed by fitting with the calculated reflectivity curves which were also normalized with the same reference curves. The XRR analyses show that the variation of the positions of the thickness fringes in the measured reflectivity curve is caused by the interference effect from two oxide layers of different refractive indices and of different thicknesses with each other. The result indicates that there exists a SiO2 interlayer of a different refractive index between the SiO2 overlayer and the Si substrate. The analytical method used in the study determines the thickness of a ultra-thin SiO2 layer on Si with low uncertainty.

Abstract: Nuclear resonant scattering (NRS) methods allow to determine diffusion coefficients and jump directions. The capability to measure the diffusion mechanism in ordered intermetallics on atomic scale by mean of NRS was shown in various experiments and in different geometries (transmission [1,2], Bragg [3], grazing incidence [4]). A combination of NRS and grazing incidence geometry can be used as a very sensitive tool to investigate thin films or near-surface-regions [4]. Fe3Si with a D03 structure stable at high temperature and with a well known diffusion mechanism was chosen for this investigation.