Scanning tunneling microscopy investigation of the electronic structure across LaAlO$_{3}$/SrTiO$_{3}$ heterointerfaces

Atomically controlled polarity discontinuities induced unusual charge states have been found in the model interface between two insulating perovskite oxides, LaAlO$_{3}$ and SrTiO$_{3}$. In this work, by using cross-sectional scanning tunneling microscopy, local and direct evidence of nontrival local structural and electronic information across the heterointerfaces are investigated. A combination of scanning tunneling spectroscopy analysis with atomic resolution across the LaAlO$_{3}$/SrTiO$_{3}$ heterointerface reveals how the oppositely charged atomic planes undergo electronic reconstructions and introduce a built-in electric field across the polar LaAlO$_{3}$ thin films grown on SrTiO$_{3}$ substrates. Further analysis of the related electronic and geometrical properties not only realizes the properties both in bands of electron and hole characters across the LaAlO$_{3}$/SrTiO$_{3}$ heterointerfaces but also helps to elucidate the mechanism of the interface conductivity.