Paraelectric/antiferroelectric/ferroelectric phase transformation in As-deposited ZrO2 thin films by the TiN capping engineering

Based on the engineering of the TiN capping layer, the tailoring of the crystalline phases and the paraelectric(PE)/antiferroelectric(AFE)/ferroelectric(FE) properties of nanoscale ZrO2 thin films are demonstrated without any post-annealing treatment. The capping by the TiN layer leads to the conversion of ZrO2 from the PE to the AFE electrical characteristics, while the removal of the TiN capping layer results in the AFE-to-FE phase transformation of ZrO2. The nano-beam electron diffraction, high-resolution transmission electron microscopy and X-ray diffraction characterizations identify the presence of the AFE tetragonal and FE orthorhombic phases in ZrO2, and the observations reveal the emergence of the out-of-plane compressive and in-plane tensile strains in the ZrO2 layers by the TiN capping layer as well. The results demonstrate the significant impact of the TiN capping layer effect on the crystalline phases and dielectric properties of nanoscale thin films at a low temperature, which may play an important role in the FE/AFE applications which need a low thermal budget. [Display omitted] •The TiN capping layer induces ZrO2 transformation from paraelectric amorphous phase to antiferroelectric tetragonal phase.•Etching TiN away results in relaxation of ZrO2 from antiferroelectric tetragonal phase to ferroelectric orthorhombic phase.•The TiN layer can modulate the antiferroelectric and ferroelectric phases in ZrO2 thin films without high-temperature annealing.