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224 reciprocal lattice points of single layers with constant Sn content on v-Ge measured by XRD-2DRSM. The Sn content (film thicknesses) of was 1.0% , 2.2% , 2.5% , 2.7% , and 5.8% . The dotted lines represent the calculated reciprocal lattice sites for strained-relaxed crystals and pseudomorphic crystals. The solid lines represent the calculated reciprocal lattice sites of strain-relaxed crystals complying with Vegard’s law. Open symbols indicate 224 reciprocal lattice points for as-grown samples and solid symbols (black, gray, and blue: without Sn precipitation, red and green: with Sn precipitation) for PDA-treated samples.
224 reciprocal lattice points measured by XRD-2DRSM showing the Sn content variation and the strain relaxation behavior of each layer. The sample structure was . Symbols and colors indicate ○: as-grown, △: first-step PDA, ◻: second-step PDA, ◇: third-step PDA, white: bottom-GeSn, gray: middle-GeSn, and black: top-GeSn.
Dislocation morphology, interface, and reciprocal lattice structure of the sample after the growth of a Ge layer on the step-graded layer stack shown in Fig. 2. (a) XTEM image taken by the weak-beam method at with . (b) High resolution XTEM image of the epitaxial interface. (c) XRD-2DRSM result for asymmetric 224 Brag reflections. Right (top) of the figure shows a diffraction intensity profile along the line . The observed profiles (dot curves) consist of a strained Ge (red), top (blue), middle (green), bottom (gray), and virtual Ge peak (black).
The DSR [%] derived from Fig. 2 for respective GeSn layers at each growth and PDA cycle.
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