Electrophysical characteristics of hafnium oxide and barium strontium titanate ferroelectric films

Electrophysical properties of hafnium oxide (HfO2) and barium strontium titanate of the composition (BST) thin films of various thicknesses from 20 nm to 250 nm are studied. Capacitance-voltage characteristics of Ni/HfO2/Si and Ni/BST/Si structures have been measured. The hysteresis loops width values are obtained depending on the films thickness. It is shown, that as the films thickness increases, the surface roughness and grain size increase. Calculated the exponential growth index values were β = 1.4 for HfO2, and β = 0.5 for BST films. Based on the local hysteresis loops results obtained in the polarization switching spectroscopy mode, coercive field values for studied films of various thicknesses were calculated, and «scaling» effect was found. It has been found that BST films are more ferroelectric «soft» material compared to HfO2 films at the same thicknesses.