Transfer of High-Temperature-Sputtered BiFeO3 Thin Films onto Flexible Substrates Using α-MoO3 Layers.

ABSTRACT

Inducing external strains on highly oriented thin films transferred onto mechanically deformable substrates enables a drastic enhancement of their ferroelectric, magnetic, and electronic performances, which cannot be achieved in films on rigid single crystals. Herein, the growth and diffusion behaviors of BiFeO3 thin films grown at various temperatures is reported on α-MoO3 layers of different thicknesses using sputtering. When the BiFeO3 thin films are deposited at a high temperature, significant diffusion of Fe into α-MoO3 occurs, producing the Fe1.89Mo4.11O7 phase and suppressing the maintenance of the 2D structure of the α-MoO3 layers. Although lowering the deposition temperature alleviates the diffusion yielding the survival of the α-MoO3 layer, enabling exfoliation, the BiFeO3 is amorphous and the formation of the Fe1.89Mo4.11O7 phase cannot be suppressed at the crystallization temperature. High-temperature-grown BiFeO3 thin films are successfully transferred onto flexible substrates via mechanical exfoliation by introducing a blocking layer of Au and measured the ferroelectric properties of the transferred films.