Probing Surface and Bulk Electrochemical Processes on the LaAlO3-SrTiO3 Interface

Local electrochemical phenomena on the surfaces of the LaAlO3-SrTiO3 heterostructure are explored using unipolar and bipolar dynamic electrochemical strain microscopy (D-ESM). The D-ESM suggests the presence of at least two distinct electrochemical processes, Including fast reversible low-voltage process and slow high-voltage process. The latter process Is associated with static surface deformations In the sub-nanometer regime. These behaviors are compared with Kelvin probe force microscopy hysteresis data. The possible origins of observed phenomena are discussed, and these studies suggest that charge-writing behavior in LAO-STO includes a strong surface/bulk electrochemical component and is more complicated than simple screening by surface adsorbates.