Figure 2.

(a) θ-2θ XRD scans of (4 nm/28 nm) Bi₂Te₃/GeTe (black line) and (4 nm/56 nm) Bi₂Te₃/GeTe (red line) heterostructure films focusing on the GeTe (0006) XRD peak close to the mica (001) specular rod. Reciprocal space maps of (b) 60 nm Bi₂Te₃ films and (c) (4 nm/56 nm) Bi₂Te₃/GeTe heterostructure films around the Bi₂Te₃ (00.18) and the GeTe (0006) peak, respectively. (d) Fitting of the GeTe (0006) XRD peak for the (4 nm/28 nm) Bi₂Te₃/GeTe heterostructure. The experimental data points are the open circles. For fitting, six peaks were used which positions and area ratios were obtained from the RHEED data in Figure 1c. The area ratios of the six XRD peaks are shown in the inset. For calculating the peak positions of the six peaks, the in-plane strain as shown in Figure 1c has first to be transformed into the out-of-plane strain using eq 2.