Fig. 3

Single-crystalline-level conductive property of \({\mathrm{BLSO}}_{(0001){\mathrm{Al}}_{2}{\mathrm{O}}_{3}}^{{\mathrm{BaZrO}}_{3}/\mathrm{MgO}}\). a The sheet resistance of \({\mathrm{BLSO}}_{(0001){\mathrm{Al}}_{2}{\mathrm{O}}_{3}}^{{\mathrm{BaZrO}}_{3}/\mathrm{MgO}}\) is ~ 50 times lower than that of \({\mathrm{BLSO}}_{(0001){\mathrm{Al}}_{2}{\mathrm{O}}_{3}}\) and is comparable to those of single-crystalline BLSO epitaxial films grown on KTaO₃, SrTiO₃, and MgO. The inset shows that the resistivities ρ, normalized by the 400 K resistivity ρ_{400 K}, of \({\mathrm{BLSO}}_{(0001){\mathrm{Al}}_{2}{\mathrm{O}}_{3}}^{{\mathrm{BaZrO}}_{3}/\mathrm{MgO}}\), \({\mathrm{BLSO}}_{(001){\mathrm{KTaO}}_{3}}\), \({\mathrm{BLSO}}_{(001){\mathrm{SrTiO}}_{3}}\), and \({\mathrm{BLSO}}_{(001)\mathrm{MgO}}\) increase above 150 K, indicating metallicity near room temperature. b The sheet resistances of \({\mathrm{BLSO}}_{(0001){\mathrm{Al}}_{2}{\mathrm{O}}_{3}}^{{\mathrm{BaZrO}}_{3}/\mathrm{MgO}}\) and \({\mathrm{BLSO}}_{(0001){\mathrm{Al}}_{2}{\mathrm{O}}_{3}}^{\mathrm{MgO}}\) decrease with increasing template layer thickness and are saturated above 10–20-nm-thick template layers. The dashed line indicates the sheet resistance of \({\mathrm{BLSO}}_{(0001){\mathrm{Al}}_{2}{\mathrm{O}}_{3}}\). c The lower resistivity of \({\mathrm{BLSO}}_{(0001){\mathrm{Al}}_{2}{\mathrm{O}}_{3}}^{{\mathrm{BaZrO}}_{3}/\mathrm{MgO}}\) with a thicker BaZrO₃ template layer is attributed to enhanced crystallinity, as evidenced by a smaller full-width at half-maximum. d Compared with \({\mathrm{BLSO}}_{(0001){\mathrm{Al}}_{2}{\mathrm{O}}_{3}}\), there are fewer scattering centres for free electrons in \({\mathrm{BLSO}}_{(0001){\mathrm{Al}}_{2}{\mathrm{O}}_{3}}^{{\mathrm{BaZrO}}_{3}/\mathrm{MgO}}\)