Enhancement of Ferroelectricity in Hf _0.5 Zr _0.5 O ₂ via Pre-Crystallization and Interface Engineering at Ultra-Low Temperature (300 °C) Annealing

The interface degradation between ferroelectric film and surrounding layers limits the endurance of hafnia ferroelectric devices significantly. This letter proposes a promising TiN/TZHZT/TiN structure with TiO<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub>/ZrO<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> bi-interlayers on both sides of a sub-7 nm Hf<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.5</sub>Zr<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.5</sub>O<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> (HZO). The TZHZT sample underwent ultra-low temperature annealing at 300 °C demonstrates exceptional ferroelectric properties, <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">i.e.</i> significant remnant polarization (2<italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">P_r</i>=28.2 μC/cm<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup>), appropriate coercive field (<italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">E_c</i>=1.7 MV/cm), and excellent endurance exceeding 10<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">10</sup> cycles. Achieved results are attributed to the synergistic effects of dual interlayer engineering. Specifically, the ZrO<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> interlayer promotes the growth of ferroelectric grains through the formation of seed crystals, leading to larger grain size after annealing. Meanwhile, the TiO<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> interlayer enhances tensile stress and oxygen enrichment, thereby improving both 2<italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">P_r</i> and endurance. Moreover, the ZrO<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> interlayer effectively compensates the deficiency of breakdown strength for TiO<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> layer.