Abstract
Bismuth ferrite (BiFeO3, BFO), a multiferroic material possessing both ferroelectric and several magnetic orders at room temperature, is studied by scanning probe microscopy (SPM) in this dissertation. Nanoscale ferroelectric properties including domain distribution, local hysteresis, and local poling are explored by piezoresponse force microscopy (PFM), one of the analyzing tools based on SPM. The magnetic response after an electrical poling is also studied by combining PFM and magnetic force microscopy (MFM), an analyzing tool to investigate nanoscale magnetic domains based on SPM. BFO thin films were produced by magnetron sputtering at 350 □C. With Pt/Ti/SiO2/Si substrates, BFO films showed good ferroelectricity with obvious hysteresis behavior and piezoelectric coefficients as high as 50 pm/V. However, with LNO/Pt/Ti/SiO2/Si substrate, unstable piezoresponse signal was shown. Direct domain writing using PFM on BFO films was successfully executed over large regions and on single grains. Different voltages were pre-biased at certain areas to show different polarities. A large voltage pulse was also added on a single domain to show reversed polarization. However, the magnetic response after an electrical poling was not observed due to the interference of an electrostatic force.