Figure 1

(a)–(c) AFM topography of ${\mathrm{SrRuO}}_3$ thin films for different thickness values ($t$) of (a) 2, (b) 4, and (c) 27 uc. (d) Topography of rough film with $t=4\mathrm{uc}$ obtained from much faster growth rate. All images are $2\mu \mathrm{m}\times 2\mu \mathrm{m}$ in size. (e) Temperature ($T$) dependence of the normalized resistivity $\rho (T)/\rho (300\mathrm{K})$ of ${\mathrm{SrRuO}}_3$ thin films for $t$ of 2–46 uc. The ${\mathrm{SrRuO}}_3$ films remain metallic down to 2 uc. The inset shows the $\rho (T)/\rho (300\mathrm{K})$ of the rough film with $t=4\mathrm{uc}$.Reuse & Permissions

Figure 2

(a) $t$ dependence of $T_C$ values. Experimental $T_C$ values (black solid circles) were obtained from the peak $T$ positions in the inset in Fig. 1b. $T_C$ values were also estimated based on the Stoner model, i.e., Eq. (2), using values for the nonmagnetic density of state at the Fermi level ($N_0$) estimated from in situ STS studies (blue open triangles) and first-principles calculations (red open squares). (b) $t$ dependence of $\rho (20\mathrm{K})$. The solid line is the classical theoretical prediction based on the increased surface scattering.Reuse & Permissions

Figure 3

Plot of the tunneling current $I_t$ versus tip bias voltage $V_{\mathrm{tip}}$ obtained from ${\mathrm{SrRuO}}_3$ films grown on a Nb-doped ${\mathrm{SrTiO}}_3$ substrate. The inset shows the $t$ dependence of the tunneling conductance ($d{I}_t/d{V}_{\mathrm{tip}}$) at $V_{\mathrm{tip}}=0\mathrm{V}$. The $d{I}_t/d{V}_{\mathrm{tip}}(0\mathrm{V})$ values show a monotonic decrease for decreasing $t$ and remain finite down to 1 uc. The red solid line indicates the $d{I}_t/d{V}_{\mathrm{tip}}(0\mathrm{V})$ value for a 50-uc film. Each curve is averaged over an area of $100\mathrm{nm}\times 100\mathrm{nm}$ by a grid spectroscopic mode with $20\times 20$ sampling pixels. All STS measurements were carried out at room temperature with the same tip under identical scanning conditions, namely, $I_t=0.1\mathrm{nA}$ and $V_{\mathrm{tip}}=0.5\mathrm{V}$.Reuse & Permissions

Figure 4

(a) Schematic model systems: 1 and 4 uc of ${\mathrm{SrRuO}}_3$ on 2 uc of ${\mathrm{SrTiO}}_3$. The green and blue squares represent the metal-oxygen octahedra with ${\mathrm{Ru}}^{4+}$ and ${\mathrm{Ti}}^{4+}$ ions, respectively. The symbol of $S\mathrm{\text{−}}i$ indicates the $i$th ${\mathrm{SrRuO}}_3$ layer from the surface. (b) Calculated nonmagnetic pDOS (gray) for the middle ${\mathrm{SrRuO}}_3$ layer in films with $t=1–4\mathrm{uc}$. Note that the pDOS at 0 eV decreases with decreasing $t$. (c) Orbital configurations of the $t_{2g}$ electrons of ${\mathrm{Ru}}^{4+}$ ions in the 1 uc ${\mathrm{SrRuO}}_3$ film. The $d_{xy}$ orbitals (red) are hybridized with the oxygen $2p$ orbitals (not shown) and form an infinite 2D sheet. On the other hand, because of the truncation in the $z$ direction, the $d_{yz}$ or $d_{zx}$ orbitals (blue) form a 1D strip. The Ti-oxygen octahedra are shown in sky blue. (d) Orbital configurations of the $t_{2g}$ electrons of ${\mathrm{Ru}}^{4+}$ ions in the 4-uc ${\mathrm{SrRuO}}_3$ film. (e) Calculated pDOS with ferromagnetic configurations for the middle ${\mathrm{SrRuO}}_3$ layer in films with $t=1–4\mathrm{uc}$. The majority and minority spin states are colored in blue (filled) and red (unfilled), respectively.Reuse & Permissions