Electromechanical Response from LaAlO3/SrTiO3 Heterostructures

摘要

LaAlO3 ultrathin films, 10 unit cells in thickness, have been deposited epitaxially on TiO(2-)terminated (001) SrTiO3 substrates with various 02 pressures. Electromechanical response from the LaAlO3/SrTiO3 heterostructures is studied using combined piezoresponse force microscopy,electrostatic force microscopy and scanning Kelvin probe microsopy. Oxygen vacancies are found to be responsible for the 'observed piezoelectric response but Only for samples deposited with an oxygen pressure lower than10(-5) mbar. However, ambient humidity is demonstrated to have a significant effect on the electromechanical response. The observations are discussed in terms of modulations on the intrinsic electodstriction in LAO/STO by an electric field induced by nonuniform distribution of either Oxygen vacancies in the bulk or ionic adSorbates on the surface of LAO.