Investigation on hydrogen annealing effect for various ferroelectric films by electrostatic force microscope

Scanning probe microscope with a dc bias and an ac modulation signal applied to the probing tip has been quite successful for investigating the characteristics in a sub-micron scale for the high density ferroelectric memory application field. The degradation of ferroelectric films—PbZr0.4Ti0.6O3 (PZT) and Bi3.25La0.75Ti3O12 (BLT)—caused by the hydrogen forming gas annealing is investigated in a microscopic scale by using an electrostatic force microscope (EFM). From the first harmonic signal of EFM, we obtained different polarization behaviors from as-grown and hydrogen-annealed ferroelectric films. We found that the hydrogen forming gas annealing is degrading the ferroelectric film with no catalyst top electrode on top of the film. It is believed that the annealing process causes the diffusion of hydrogen into the ferroelectric film resulting in the destruction of polarization in these materials. We speculate that the different degradation behavior among these materials (PZT and BLT) is due to the different cohesivity of hydrogen in these materials.