Junction size dependence of ferroelectric properties in e-beam patterned BaTiO_3 ferroelectric tunnel junctions

摘要

We investigate the switching characteristics in BaTiO_3-based ferroelectric tunnel junctions patterned in a capacitive geometry with circular Ru top electrode with diameters ranging from ～430 to 2300 nm. Two different patterning schemes, viz., lift-off and ion-milling, have been employed to examine the variations in the ferroelectric polarization, switching, and tunnel electro-resistance resulting from differences in the pattering processes. The values of polarization switching field are measured and compared for junctions of different diameter in the samples fabricated using both patterning schemes. We do not find any specific dependence of polarization switching bias on the size of junctions in both sample stacks. The junctions in the ion-milled sample show up to three orders of resistance change by polarization switching and the polarization retention is found to improve with increasing junction diameter. However, similar switching is absent in the lift-off sample, highlighting the effect of patterning scheme on the polarization retention.