Earnshaw Medal

Earnshaw 2009 Nominees: Raymond McQuaid, QUB

Domain dynamics and switching behaviour in ferroelectric mesowires
The drive for device miniaturisation in ferroelectric memories (FeRam), coupled with the associated effects of reduced size, provides complementary interest for both technology and fundamental research. Additionally, a transition from 2D planar capacitor structures to more morphologically complex 3D components is anticipated within the next few years in order to increase bit densities. Whilst the functional behaviour of ‘thin-films’ is well understood, polarisation switching in more complex 3D nanoshapes is much less well established. Hence, single crystalline BaTiO₃ mesowires (1m in width) were fabricated by focused ion beam milling and tested electrically. An hysteretic capacitance-voltage (CV) profile was obtained under axial biasing and compared to that of a planar sheet. Contrary to an argument based on the increased influence of surface drag suppressing domain wall motion in a wire geometry, the 1m wire samples were observed to be easier to switch. Using appropriate static domain imagery from prior investigations this was rationalised in terms of a more ordered domain sequence in the wires. In addition, a preliminary investigation into the influence of shape engineering was conducted by introducing notches along 1m wires. Somewhat surprisingly, electrical testing suggested notching to have negligible effect on switching behaviour.

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