Study Of X-Ray Scacttering On Supersmooth Surface

The complex space soft X-ray and EUV telescope is mainly applied to the spatialenvironment monitoring and scientific studies for the solar and other celestialactivities. According to the Wolter-I type mirror adopted in this system, thin filmdensity measurement, surface roughness measurement of supersmooth surface andanomalous surface scattering (ASS) phenomenon are studied in detail.1．Distorted wave Born approximation (DWBA) theory and perturbation theory(PT) have been introduced. Furthermore, first order perturbation theory (FOPT)formulas have been deduced to extract power spectral density (PSD) functions of thesurface roughness directly from the measured scattering distribution. At last, theconditions of applicability of FOPT have been discussed. The measurement of thescattering diagram should be carried out at not too large incidence angle andscattering angle. And the RMS roughnessσ does not exceed1-2.5nm, the largervalue corresponding to the case of light materials.2． Firstly, the X-ray scatting distribution measurement facility has beenintroduced. Secondly, Au thin film and Ni thin film have been evaporated by electronbeam coater, Mo thin film has been sputtered by magnetron sputtering coatingmachine, and A₂O₃thin films have been deposited by Atomic layer deposition (ALD).Thirdly, thin film thickness has been calculated according to the modified Braggequation, which indicates that ALD is a thin film coating method with high uniformityand thickness controllability. Lastly, a simple method to evaluate thin film massdensity accurately from the X-ray reflectivity distribution has been given, whichnamed XRR_DENmethod. According to the measured mass density, optical constant of thin film could be calculated. This is very important for evaluating the surfaceroughness PSD function of thin film sample from X-ray scattering distribution.3．The instrument was determined according to the analysis of the factors causingsystematic errors on the PSD function measurement. These factors include the effectsof the finite width of the detector slit, the width of the primary beam and the systemalignment error etc. Then the scattering indicatrix for different optical surfaces andthin film samples were measured, and one-dimensional PSD functions and effectiveRMS roughness were calculated by FOPT. Which coincide well with themeasurements of atomic force microscopy(AFM)。The results demonstrated thatFOPT is validity for measuring the surface roughness of supersmooth surface.Specifically, calculating optical constants from the experimentally measured massdensities by XRR_DENof the studied thin film samples could improve the measurementaccuracy.4．There presents an anomalous surface scattering (ASS) phenomenon during themeasurement of surface roughness of smooth surface. Experimental results indicatethat the anomalous scattering angle is various with the kind of materials used undercertain incidence wavelength and change slightly with the glancing angle and RMSsurface roughness. Moreover, all the measured anomalous scattering angles areslightly smaller than the critical angle values, and the measurement errors range from-8%to-0.3%。On the other hand, the anomalous surface scattering phenomenon ismore obviously as the increasing of grazing incidence angle and surface roughness.The reasons of anomalous surface scattering occurring have been analyzed. This is afoundation of future study about the anomalous surface scattering affect on the imagequality of grazing incidence image system.