Preparation of epitaxial oxide thin films on Si(100) substrates with CoSi2 surface layers

Yttria-stabilized ZrO2 (YSZ) and CeO2 films have been epitaxially grown by electron beam evaporation on Si(100) substrates with CoSi2 buffer layers prepared by ion implantation and annealing. Microstructure and morphology of these films have been characterized by X-ray diffraction (XRD), Rutherford backscattering spectroscopy with channeling (RBS-C), and scanning electron microscopy (SEM). θ-2θ scan XRD spectra show that CeO2 films have (111) orientation on CoSi2/Si(100) substrates. However, the orientation of YSZ films is related with the deposition parameters. In the high oxygen pressure range (approx. 10-6 mbar), YSZ films have the pure (100) orientation, whereas in the low oxygen pressure regime (approx. 10-7 mbar), YSZ films have (111) and (100) mixed orientations. For a CeO2/YSZ/CoSi2/Si(100) multilayer system deposited under the optimum conditions, each layer grown epitaxially has the same orientation as the Si substrate. RBS-C measurements prove that both YSZ and CeO2 films have considerably good crystalline quality, the minimum yield, χmin, for Ce signal is only 18%. In RBS-C spectra, there is no interdiffusion between films and the Si substrate. φ XRD scans indicate that in-plane epitaxial alignment is the same in respect to the Si(100) substrate. The thermal and chemical stability of CoSi2 layer makes the growth of YSZ and CeO2 films easier on the CoSi2/Si(100) structure than on pure the Si(100) substrate. Surface morphology of YSZ and CeO2 films can be optimized by the control of oxygen pressure and deposition rate. It was found that roughness of films was minimized by reducing the deposition rate (approx. 0.5 angstrom/s). Pinholes in the film can be avoided at a relatively high oxygen pressure (approx. 10-6 mbar).