Atomic-scale structure investigation of CeO2/YSZ/Si hetero-interface by high resolution analytical electron microscope

The interface structure and the chemical state on the orientation of a CeO2/YSZ (yttria stabilized zirconia)/Si and YSZ/CeO2/Si hetero structure have been considered using a high-resolution transmission electron microscope (HRETM) equipped with an analytical setup. Although both films showed a columnar structure, they had different orientations. In the YSZ/CeO2/Si hetero structure, the CeO2 layer has a (111) orientation without any in-plane orientation. TEM-EELS (electron energy loss spectroscopy) and TEM-EDS (energy dispersive X-ray spectroscopy) analyses showed that there were reacted interface layers due to a reduction of the CeO2 layer and the oxidation of the Si substrate. In the CeO2/YSZ/Si hetero structure, the CeO2 layer preferentially had a 001 orientation. The quality of the 001 orientation was increased on an ultra-thin YSZ layer. The interface of CeO2/YSZ (thick) has a semi-coherent interface with misfit dislocations. The interface of CeO2/YSZ (thin) has been ambiguous due to a disordered structure of the YSZ layer. A TEM-EDS analysis showed that there was only a reacted interface layer due to oxidation of die Si substrate. This means that a thin YSZ layer effects the passivation layer for the reduction of a thermodynamically unstable CeO2 layer against Si, as well as an epitaxy transmission from the Si substrate into the CeO2 layer.