STUDY OF FERROELECTRIC PROPERTIES OF MULTIFERROIC THIN FILMS

Abstract

In the presented work, (La and Mn) doped BFO (of composition Bio9Lao 1 Fe095Mn00503 (BLFMO)) thin films is synthesize on the highly Boron doped p-type Si (100) substrate by the spin coating method. The observations are concentrated on the study of ferroelectric properties (as hysteresis loop characteristics, fatigue characteristics, IN characteristics and switching properties) measurement. In this work effects ZnO buffer layer between the substrate and ferroelectric film is studied for which 12 layers of BLFMO are grown on the substrate and on the ZnO buffer layer based substrate and results are compared. ZnO buffer layered sample gives better results in fatigue characteristic and in IN characteristic. Again the effects of thickness of ferroelectric film on these ferroelectric properties are measured, for which 8, 12, 15, 17, 20 layers of BLFMO are grown on the ZnO buffer layer based substrate. The XRD patterns of films are taken using Advanced Bruker D8 dffractorneter with Ni-filtered CuKa radiation of wavelength 1.54 A. it confirms the formation of ZnO and BLFMO, and lattice parameters and crystalline size analysis (table 3.1) done using software Crystal Sleuth for all samples. The AFM 2D and 3D images taken using NT-MDT & Ntegra and the grain size and average roughness is increasing with film • thickness. The ferroelectric properties are found better in 12 layered film, the remnant polarization (Pr) is at 50 Hz is 236 .tC/cm2 but it decreases very rapidly on increasing frequency at 500Hz it remains about 20 xC/cm2. The fatigue characteristic and IN characteristic are improved on applying the ZnO buffer layer. The buffer layer and thickness of the film are reduced the leakage current in the film and leakage current is found to ruled according to the Poole-Frankel conduction mechanism. The leakage current improves from lmA/cm2 to 0.1mA/cm2 on inserting buffer layer. The switching time and peak switching current in film of 12 layer is studied with square and triangular waveform.