• Skopin, Evgeniy

Abstract

<jats:p> Sub-10 nm thick gadolinium-doped hafnia (Gd:HfO<jats:sub>2</jats:sub>) layers were grown in metal–insulator–metal (TiN/Gd:HfO<jats:sub>2</jats:sub>/TiN) stacks using a plasma-enhanced atomic layer deposition process. Thermally annealed Gd:HfO<jats:sub>2</jats:sub> layers with a thickness of 8.8, 6.6, and 4.4 nm exhibited orthorhombic crystalline structure and showed ferroelectric properties. Indeed, polarization vs electric field hysteresis loops were recorded with 2P<jats:sub> r</jats:sub> polarization ranging from 2 to 20 μC/cm<jats:sup>2</jats:sup>. The studied layers showed the same coercive electric field (∼2 MV/cm). Consequently, polarization switching voltage between +P<jats:sub> r</jats:sub> and −P<jats:sub> r</jats:sub> decreased down to 0.9 V for the thinnest layer. Remanent polarization cycling showed a strong wake-up effect, with no fatigue, up to 10<jats:sup>9</jats:sup>, followed by a stabilization up to 10<jats:sup>10</jats:sup> cycles, where 2P<jats:sub> r</jats:sub> reached 33 μC/cm<jats:sup>2</jats:sup> for 8.8 nm Gd:HfO<jats:sub>2</jats:sub>. This endurance result and the absence of noticeable remanent polarization fatigue can be attributed to the optimal chemical composition of the TiN/Gd:HfO<jats:sub>2</jats:sub> interface, which is supposed to be at the origin of defect generation, mostly oxygen vacancies, that leads to ferroelectric polarization fatigue. </jats:p>

Topics

• impedance spectroscopy
• Oxygen
• fatigue
• chemical composition
• defect
• tin
• Gadolinium
• atomic layer deposition