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Estimated MBE growth window for in conventional MBE using solid metal sources. The diagram was calculated using thermodynamic data from Refs. 20 and 21, following the same approach as in Ref. 6. A sticking coefficient of 1 is assumed for Ti, consistent with experimental data in the literature (Ref. 6). At the oxygen pressures used in MBE, Sr is assumed to oxidize immediately to SrO, consistent with experiments (Ref. 7) and thermodynamic data (Ref. 16). Shown are the equilibrium lines for two reactions (red dashed lines) and (blue solid lines). The two lines for each reaction indicate the uncertainty in the thermodynamic data used for the estimates. Above the lower solid line, condenses to react with to and below the dashed line any excess will evaporate. Thus phase-pure stoichiometric films grow in the window (hatched area) between the lines.
High-resolution x-ray diffraction scans around the 002 reflections of homoepitaxial films and substrates. The arrows indicate the film peak. All films were grown at a substrate temperature of with an oxygen BEP of and at TTIP/Sr ratios of (a) 55.4, (b) 53.3, (c) 42.13, (d) 41, and (e) 39.5, respectively. The film thicknesses were between 120 and 170 nm. The scans are displayed in order of increasing nonstoichiometry away from the middle scan for the stoichiometric film shown in (c).
Out-of-plane lattice parameter as a function of TTIP/Sr BEP ratio for epitaxial films grown on at (a) , (b) , and (c) . All films were grown using an oxygen BEP of . The darker gray-shaded region shows the growth window for stoichiometric films with a lattice parameter that is equivalent to that of the substrate at each temperature.
Growth window for stoichiometric films for two different oxygen BEPs of (black circles) and (green triangles). Shown is the range of TTIP/Sr ratios that results in stoichiometric films as a function of temperature and oxygen BEP. The lines are shown as a guide to the eye.
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