UBC Theses and Dissertations
Characterization of inconel/carbon multilayer mirrors for 45 Å wavelength Aouadi, Mohamed Samir
This thesis reports on the study of x-ray mirrors that operate at normal incidence for 45 Å wavelength used in applications such as x-ray microscopy, x-ray astronomy, x ray lithography, x-ray imaging, and x-ray lasers. These mirrors are fabricated by alternately depositing two materials of different scattering factors to form a multilayer structure. A theoretical treatment to identify new combinations of materials for these mirrors was provided. Carbon and inconel were then selected for ‘low index’ and ‘high index’ layers, respectively, in the multilayer system. The thin film laboratory at U.B.C. was set-up for x-ray multilayer research by automating a sputter coater to allow for the deposition of multilayers and by developing the appropriate software for data analysis. The optical and structural properties, the chemical composition, and the thermal stability of the deposited materials were measured as a function of argon pressure and substrate bias voltage using X-ray Photoelectron Spectroscopy (XPS), X-ray Diffraction (XRD), Grazing X-ray Reflectometry (GXR), and Spectroscopic Ellipsometry (SE). Multilayers grown at a low pressure and a moderate substrate bias (—40 to —80 V) were found to be the most suitable for x-ray reflectors. Also, samples for second order reflection (period = 45 Å) were found to be more stable than samples for first order reflection (period = 22.5 Å). In situ ellipsometry was used to monitor the deposition of single layers and multilayers of inconel and carbon. Valuable information was obtained regarding the early stages of film growth, interdiffusion at the interfaces, porosity of the films, etc. The coalescence thickness of inconel was found to be 10 Å . Interdiffusion was found to occur at the ‘carbon-on-inconel’ interlace because of the rough underlying inconel layer but not at the ‘inconel-on-carbon’ interface because of the smooth underlying carbon layer. Interdifusion at the ‘carbon-on-inconel’ layer was also found to increase with the number of layers. The control routine worked well. However, timing was found to better control the reproducibility of the thickness.
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