Deposition of LaNiO3 nanocolumnar buffer layer for the growth of BiFeO3 - Ni0 5Zn0 5Fe2O4 Composite film

Abstract

A multiferroic composite film with a combination of ferrimagnetic Ni0 5Zn0 5Fe2O4 (NZFO) and multiferroic BiFeO3 (BFO) was grown on the LaNiO3 (LNO) buffered Si (001) substrate using dual-target RF magnetron co-sputtering LNO polycrystalline films were prepared for a nanocolumnar structure and were confirmed with SEM The effect of temperature partial oxygen pressure (pO2) and working pressure are presented here where at a lower working pressure 10 and 20 mtorr no columnar structures devoloped due to a deviated Ni/La ratio In response to changes in temperature the columns become finer as temperature decreased The diameters of the columns were 59 4 69 0 and 97 3 nm at 550 650 and 750oC respectively as measured using AFM Higher pO2 revealed fine columns which was confirmed via SEM Such a nanostructure is expected to minimize the “substrate clamp” problem that limits the applications of this type of composite films BFO + NZFO composite films were deposited on columnar structures with different diameters Exchange bias was provided to ensure there was no interfacial diffusion between the composite were BFO particles embedded in the NZFO matrix as confirmed with TEM The longitudinal coefficient (?E L) and transverse coefficient (?E T) were measured All results showed ?E T to be larger than ?E L BFO and LNO showed grain epitaxy cause higher ?E L that decreased with increases in thickness This residual strain was relaxed by the columns in the in-plane direction; thus ?E T enhanced as thickness increased For composites deposited on LNO of the fine columns ?E L and ?E T are 2 056 and 2 759 V?Ohm-1cm-1 under a 0 bias field at the resonance frequency of 4 kHz as the thickness increased to 300 nm and the ?E L and ?E T are 1 292 and 3 071 V?Ohm-1cm-1 under a 0 bias field at the resonance frequency of 4 kHz

Date of Award	2018 Aug 18
Original language	English
Supervisor	Xiao-Ding Qi (Supervisor)