Effects of Residual Stress on the Ferroelectric Properties of Al_0.8Sc_0.2N Films Sandwiched Between Pt or W Electrodes

In this work, the impacts of the residual stress on the structural and ferroelectric properties of Al0.8Sc0.2N films clamped with different metal electrodes (Pt and W) were investigated. The Pt/Al<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$_{\mathbf {0.8}}$ </tex-math></inline-formula>Sc0.2N/Pt capacitors exhibited enhanced ferroelectric performance, with coercive fields (<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${E} _{\text {c}}$ </tex-math></inline-formula>) reduced by 0.2 MV/cm, leakage currents reduced by one order of magnitude and stable polarization switching across frequencies. These improvements are attributed to better crystallographic orientation and larger grain sizes driven by tensile stress. In contrast, W/Al0.8Sc0.2N/W capacitors showed larger leakage currents, higher <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${E} _{\text {c}}$ </tex-math></inline-formula>, and a greater susceptibility to breakdown. Moreover, the W samples showed diminished retention characteristics, with a 50% loss in nonswitched polarization at <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$10^{{4}}$ </tex-math></inline-formula> s compared to the Pt counterparts. These issues were related to the compressive stress between W and Al0.8Sc0.2N, resulting in more defects that impeded polarization switching. The findings suggest that the engineering of stress through electrode selection is essential for optimizing the performance of AlScN-based ferroelectric devices.