Microscale materials design using focused proton-beam writing

In this study, we fabricated bismuth titanate (Bi₄Ti₃O₁₂, BIT) thick films by the polyvinylpyrrolidone (PVP) molecules-enhanced metal-organic decomposition (MOD) method, and we discussed directly the micropatterning technique by the focused proton-beam irradiation method. The fabricated 1μm thick films exhibit a highly c-axis orientation, have a mirror-smooth surface, have a reduced crack density, and show ferroelectric properties. However, when the amount of PVP added was excessive, the density of the BIT thick film decreased. In the case of no PVP, the remanent polarization and coercive field value was 5.36μC/cm² and 168kV/cm, respectively, at an applied electric field of 400kV/cm. We confirmed the possibility of microfabrication of BIT thick films by proton-beam irradiation. The main irradiation conditions were an accelerated voltage of 1MeV, a focused-beam diameter of 1.3μm, and a beam current of 20pA, respectively. We fabricated smooth surface micropillars with a diameter of 5μm. From these results, we believe that the focused proton-beam irradiation is effective in realizing the BIT thick film with fine, arbitrary-shaped micropatterns.