Thermally activated recovery of electrical conductivity in ${\mathrm{LaAlO}}_3/{\mathrm{SrTiO}}_3$

Patterned structures of ${\mathrm{LaAlO}}_3/{\mathrm{SrTiO}}_3$ that exhibit a decrease in their electrical conductivity below 30 K recover their higher conductivity upon warming in a thermally activated process. Two dominant energy barriers $E_b$ are identified: $E_{b1}=0.224\pm 0.003$ eV related to conductivity recovery near $70\mathrm{K}$ and $E_{b2}=0.44\pm 0.015$ eV related to conductivity recovery near $160\mathrm{K}$. We discuss possible linkage to structural defects such as dislocations and twin boundaries.

Figure 1

(a) The sheet resistance ($R_s$) vs time at 5 K in a pattern with $d=10\mu$m. (b) The time dependence of a magnetic field applied parallel to the LAO/STO interface. (c) The time dependence of a current driven through the pattern. Inset: A sketch of a typical pattern.

Figure 2

The sheet resistance ($R_s$) as a function of temperature during cooling (dashed line, blue) and during warming (solid line, black) after increasing $R_s$ at 5 K (using the procedures shown in Fig. 1). Inset: Blowup of the low-temperature data.

Figure 3

The sheet resistance ($R_s$) as a function of time after increasing $R_s$ at 5 K (see Fig. 1), as the temperature is increased in steps near 70 K (a) and 160 K (b).

Figure 4

The sheet conductivity (${\sigma }_s$) as a function of time after increasing $R_s$ at 5 K (see Fig. 1), at different temperatures near 70 K (a) and 160 K (b). After each measurement, $R_s$ was recovered to its as-cooled value by warming the sample to 350 K. The lines are fits to Eq. (4).

Figure 5

The sheet carrier density ($n_s$) as a function of the sheet conductivity (${\sigma }_s$) at 75 K (a) and 160.5 K (b). Inset: The temperature dependence of $n_s$ in the relevant temperature range during cooling.

Figure 6

The parameter $W$ [Eq. (4)] as a function of 1/$T$ near 70 K (a) and 160 K (b). Different symbols represent different patterns. The lines are fits to Eq. (5).