Origins of Conduction at Domain Boundaries, LaAlO3/SrTiO3 and Surface for Depolarization & Size Effect

The conductions at domain boundaries due to ferroelectric polarization and LaAlO3/SrTiO3found by Ohtomo and Hwang [Nature 427, 423 (2004)] are intriguing. If these conductions are different from the conventional conductions at domain boundaries and oxide interfaces due to defects, they prove the earlier predictions [Phys. Rev. Lett. 86, 332(2001); Phys. Rev. B57, 789(1998)]. That is, when these conductions are primarily due to ferroelectric polarization as predicted, the foundations of mesoscale and nanoscale ferroelectrics should change. Considering conventional mechanisms including the high field effect as in the resistance switching (RRAM), we examine their origin and discuss these implications.