Demonstration of ferroelectricity in PLD grown HfO2-ZrO2 nanolaminates

Abstract

Ferroelectricity is demonstrated for the first time in Si(100)/SiO₂/TiN/HfO₂-ZrO₂/TiN stack using pulsed laser deposition (PLD) and the effects of temperatures, partial oxygen pressures, and thickness for the stabilization of the ferroelectric phase were mapped. Thin films deposited at a higher temperature and a higher oxygen partial pressure have a higher thickness, demonstrating a better ferroelectric response with ~12 μC/cm² remnant polarization, a leakage current of 10⁻⁷ A (at 8 V) and endurance > 10¹¹ cycles indicative of an orthorhombic crystal phase. In contrast, thin films deposited at lower temperatures and pressures does not exhibit ferroelectric behavior. These films can be attributed to having a dominant monoclinic phase, having lower grain size and increased leakage current. Finally, the effects of ZrO₂ as top and bottom layer were also investigated which showed that ZrO₂ as the top layer provided better mechanical confinement for stabilizing the orthorhombic phase instead of as the bottom layer.