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Schematic illustration of the experimental setup used for in situ x-ray studies of ALD. 24 keV x-rays are used to penetrate the 2 mm thick quartz walls. The apparatus permits the simultaneous measurement of x-ray scattering with a Cyberstar scintillation detector (Oxford Danfysik), and fluorescence, with a Vortex silicon drift detector (Radiant Detector Technologies) aligned along the sample normal. A RGA (Pfeiffer-Vacuum) is used to monitor the gas exchange.
(a) X-ray reflectivity as a function of perpendicular momentum transfer after each growth cycle, from 0 to 16 monolayers. Scans are offset by 10×. The fitted reflectivity, shown in red, overlay the data points shown in black. (b) Film thickness (solid black squares) shown on the left axis and surface roughness (open circles) shown on the right axis as function of growth cycle. As seen, the fitted film thickness increases upon the fourth growth cycle; this is accompanied by a subsequent increase in surface roughness. The solid red line is a linear fit for growth cycles 6–10, and the solid blue line is a linear fit for cycles 10–16. The growth rate decreases from per cycle to per cycle. An ex situ AFM image after 16 cycles of growth is shown in the inset.
(a) fluorescence intensity as a function of time for the 16 growth cycles. The cycle number is shown on the top axis. (b) The average change in intensity as a function of cycle number.
Scattered intensity at (solid curve) and fluorescence intensity (dotted curve) as a function of time. The DEZn pulse is shown in the shaded blue region, and the pulse is shown in the shaded red region; all other regions correspond to a purge step in Ar. Results for cycle nos. 2 and 6 are shown in (a) and (b), respectively.
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