Microstructural characterization of ferroelectric oxides thin films based on hafnia

Abstract

Since the discovery of ferroelectricity in HfO2 thin films, HfO2 based materials have become of great interest for applications such as non-volatile random-access memory devices. Morphological and atomic scale structural investigations of nanomaterials are important in further understanding of their electrical properties. The electrical behavior (C-V, I-V characteristics and polarization hysteresis loop) of multilayer structures is greatly influenced by the quality of the deposited thin films and also the quality of the interfaces between the layers. Transmission Electron Microscopy (TEM) is the most appropriate microstructural characterization technique able to provide morphological and structural information about the thin films and their interfaces. We study the morphological properties of this oxide based on hafnia because the orthorhombic phase exhibits ferroelectric properties. In this work we use a Cs probe-corrected JEM ARM 200F electron microscope, TEM-SAED and HRTEM techniques to investigate the morphological structure of HfO2 based thin films and to identify the crystalline phases of the ferroelectric oxide. The studied samples consist in thin films of HfO2 deposited on a TiN electrode and the latter was deposited on a Si (100) substrate with a native SiO2 layer. The thin films were grown by atomic layer deposition (ALD) using TEMAHf and ZyALD precursors deposited at 300oC. HRTEM technique combined with FFT (Fast Fourier Transform) analysis provides a complete characterization of morphological and structural properties of the thin film.