Structural and Nanoscale Electrical Properties of Bismuth Ferrite Thin Films Annealed in Forming Gas

The 60 nm-thick BiFeO3 (BFO) thin films with (h00) orientation were successfully grown on the LaNiO3(LNO)-buffered Pt/Ti/SiO2/Si(100) substrates. The effect of forming gas (7%H2+93%Ar) annealing (FGA) temperature (300-500) on the physical properties of the BFO thin films is investigated in this study. The x-ray diffraction results show that the higher FGA temperature results in a larger degree of deterioration of crystal quality of the BFO thin films. This change can be attributed to a loss of oxygen from the BFO thin films and the incorporation of hydrogen atoms into the lattice of the BFO thin films during FGA at a high temperature. FGA incurs an increase in surface roughness of the BFO thin films. The current maps obtained by the measurements of conductive atomic force microscope demonstrate that the leakage behaviors of BFO thin films without and with FGA at various temperatures under the breakdown electric field are different. The leakage currents are detected mostly in areas around large crystallites for BFO thin films without or with FGA at 300. In contrast, large crystallites in the BFO thin films with FGA at 400-500 are electrically leaky and the detected currents are high compared to those of BFO thin films without and with FGA at 300.