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Schematic representation of cross-sectional crystal structures (left panel) and two possible ideal termination layers (right panel) from a crystallographic point of view for (001), (110), and (111) orientated substrates.
(a)–(c) show representative surface morphology of the treated (001), (110), and (111) surfaces; the conditions of chemical etching and thermal annealing are expressed in the inset of the figures. On right side is plotted the cross-sectional profile showing the step height. The distance between two horizontal guide lines corresponds to the lattice spacing expected in single-layer-step for each crystal orientation; 0.39 nm for (001), 0.276 nm for (110), and 0.225 nm for (111) surface shown in (d), (e), and (f) respectively.
(a) Experimental configuration of TOF-MS. (b) A representative spectrum obtained from the chemically treated surface in which peaks are allocated to , , , and ions. (c) The ratio of Ti recoiled ions with respect to Sr recoiled ions is plotted as a function of the azimuthal angle, comparing the treated surface to the as-received one. The treated surfaces of all three orientations have a higher Ti/Sr ratio. Two different samples with treated (001) surface show nearly the same results (compare stars symbols with square symbols in the top panel), which indicates that the Ti/Sr ratio of the as-received and treated substrates is meaningfully different.
(a) Azimuthal angle scan of MSRI for Ti ions and Sr ions on the treated (111) surface. (b) Schematic of ionic arrangement on the (111) surfaces is shown. The dashed arrows indicate the projected direction toward the MSRI detector. Ti recoiled ions toward A or B direction are blocked by neighboring Sr ions. On the other hand, Sr recoiled ions toward and are blocked by neighboring Ti ions. The MSRI intensity of Sr ions can be reduced additionally by shadowing effect along and . The blocking/shadowing of oxygen ions and next-nearest ions would be secondary effect to produce fine structures in the spectra.
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