Fig. 3.

Structure and transport of ${\mathrm{N}\mathrm{d}}_{1-x}{\mathrm{S}\mathrm{r}}_x{\mathrm{N}\mathrm{i}\mathrm{O}}_2$ films with hole doping $x\le$ 0.225. (A–C) Atomic-resolution HAADF-STEM and elemental EELS maps of $x$ = 0.10, 0.20, and 0.225 samples, respectively. (D) Sr-${\mathrm{M}}_3$ EEL spectra from each film show a qualitative trend consistent with the expected nominal Sr doping in each sample. A similar spectrum from ${\mathrm{S}\mathrm{r}\mathrm{T}\mathrm{i}\mathrm{O}}_3$ is shown in gray for comparison. (E and F) Resistivity vs. temperature curves for the four ${\mathrm{N}\mathrm{d}}_{1-x}{\mathrm{S}\mathrm{r}}_x{\mathrm{N}\mathrm{i}\mathrm{O}}_2$ films studied here. Lightly Sr-doped ($x$ = 0.0, 0.1) films show metallic behavior with a resistive upturn near 50 to 70 K, while more strongly doped ($x$ = 0.2, 0.225) films show superconducting transitions (${\mathrm{T}}_{c,90\%R}$) at 8 and 11 K, respectively. Data for $x$ = 0.0 are from ref. 8.