Fig. 4. Structural analyses of 214:113.
(A) STEM image of the c-214/a-113 boundary within white dashed Box b in Fig. 3 (C and D). The blue arrow from points I to II shows the horizontal distance where the lattice parameters were analyzed. The out-of-plane lattice parameters of the film were analyzed along the slanted lines that run parallel to the boundary and then averaged. (B and C) Lateral variation of the lattice parameters across the region from points I to II. The bars on each point reflect the variation in lattice parameters over the slanted regions in (A). The brown solid lines indicate the bulk lattice parameters of 214. (D) Relation of TC and c. The averaged c values from regions 1, 2, and 3 in (B) and (C) are included in (D), as well as the data for bulk 214 (oxygenated and Sr-doped) and 214 films grown on LSAO substrates from (19, 32). The projected influence of a on the plot [as determined from (E)] is shown schematically by the blue arrow. The yellow dashed line is a guide for 214 on LSAO (19). Yellow, red, and blue zones have the same slope as the guide for 214 on LSAO but with different a. (E) Maximum TC versus a (7, 8, 27) for optimized cuprates. A strong dependence of TC on a (and hence the in-plane Cu-O distance) is observed with a peak in TC at a ~ 3.84 Å (7, 8). Zones A, B, and C from (D) are included on the plot to show the good fit of the experimental data of this work to the “model” plot.