Switching kinetics in nanoferroelectrics

We have measured the switching in ferroelectric capacitors of lead zirconate titanate (PZT) over three orders of magnitude in lateral area, from A = 166 to 0.19 µm 2 (the latter being the size of the smallest ferroelectric random access memory (FRAM) cells in production), and over three orders of magnitude in ramp rate of applied voltage (d E ( t )/d t = 10 7 –10 10 V cm −1 s −1 ). In accord with the model of Scott (1998 Ferroelectr. Rev. 1 1), the submicron cells follow a different dependence to the larger cells: for , the data fit a theory due to Landauer et al (the LYD model), which neglects nucleation; whereas the nanoscale devices satisfy the functional dependence predicted by Pulvari and Kuebler (the PK model), albeit with a modified coefficient. This crossover behaviour has implications for Gbit FRAM device performance at high speed. Fringing field effects measured agree with a simple model from Feynman.