Stabilization of phase-pure rhombohedral <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:mi>HfZr</mml:mi><mml:msub><mml:mi mathvariant="normal">O</mml:mi><mml:mn>4</mml:mn></mml:msub></mml:mrow></mml:math> in pulsed laser deposited thin films
Laura Bégon-Lours, Martijn Mulder, Pavan Nukala, Sytze de Graaf, Yorick A. Birkhölzer, Bart Kooi, Beatriz Noheda, Gertjan Koster, Guus Rijnders
Abstract
Controlling the crystalline structure of hafnium zirconate and its epitaxial relationship to a semiconducting electrode has high technological interest, as ferroelectric materials are key ingredients for emerging electronic devices. Using pulsed laser deposition, a phase-pure, ultrathin film of $\mathrm{HfZr}{\mathrm{O}}_{4}$ is grown epitaxially on a GaN(0001)/Si(111) template. Since standard microscopy techniques do not allow us to determine with certitude the crystalline structure of the film due to the weak scattering of oxygen, differentiated differential phase contrast scanning transmission electron microscopy is used to allow the direct imaging of oxygen columns in the film. Combined with x-ray diffraction analysis, the polar nature and rhombohedral $R3$ symmetry of the film are demonstrated.