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.

Keywords

• ferroelectricity
• pulsed laser deposition
• remnant polarization
• leakage current
• endurance
• x-ray diffraction