Nanoscale stoichiometric modifications and surface charge patterning of La1.975Sr0.025CuO4+δ crystals with a biased atomic force microscope tip

The application of a positive or negative local bias to the surface of La1.975Sr0.025CuO4+δ (LSCO) crystal by a conducting atomic force microscope tip results in accumulation of a (positive or negative, respectively) metastable charge on the surface. The surface charge initially shows diffusive dynamics with a timescale of hours, but thereafter it is shown to be stable for months. The charged regions are found by Auger electron spectroscopy to have a different stoichiometry from the surrounding material. Apart from fundamental implications for the heterostructure device construction, such surface charge manipulation could lead to AFM nanopatterning of superconducting nanoscale devices and applications in memories. (paper)