(A) study on characteristics and role as a buffer layer for $YBa_2Cu_3O_{7-x}$ of $BaTiO_3$ thin films deposited by metalorganic chemical vapor deposition

Abstract

This study reports on the characteristics and the role as a buffer layer for $YBa_2Cu_3O_{7-x}$ of the $BaTiO_{3a}$ thin films deposited on (100) p-Si, (111) InSb and indium tin oxide-coated (ITO) soda lime glass substrates by metalorganic chemical vapor deposition (MOCVD). The as-grown BaTiO$_3$ films deposited on various substrates at different temperatures below $600\,^\circ\!C$ had mirror like surfaces without having any indication of pin-holes, which was confirmed by Normarski optical microscopy. The results of the AES measurements of the $BaTiO_3$ films on (100) Si showed that the films have a stoichiometric composition containing barium, titanium, and oxygen. The ratios of the peak-to-peak intensities of the $Ba_{\text{KLL}}$, $Ti_{\text{KLL}}$, and $O_{\text{KLL}}$ peaks of the $BaTiO_3$ films were similar to those of a standard bulk $BaTiO_3$ sample. The results of X-ray diffraction (XRD) and the high-resolution cross sectional transmission electron microscopy (XTEM) results suggested as follows : The as-grown film on (100) Si exhibited a highly [110] oriented polycrystal film growth with the amorphous interfacial layer. The $BaTiO_3$ film deposited on (111) InSb at $300\,^\circ\!C$ had the peak occurring at $2 \theta=31.26\,^\circ$, which arise from the three-dimensional, partially epitaxial microcrystal at the interface. The films grown on ITO glass at substrate temperature of $400\,^\circ\!C$ and $550\,^\circ\!C$ were of an amorphous phase($\alpha-BaTiO_3$). Atomic force microscopy (AFM) measurements under ambient conditions showed that the surface morphologies of the as-grown $BaTiO_3$ film were strongly influenced not only by crystallinity such as amorphism but also by growth characteristics. The plots of capacitance-voltage (C-V) for the $BaTiO_3$ thin films on (100) Si and (111) InSb substrates were similar to that of the C-V measurements of an ordinary prepared $Al/SiO_2/Si$ diode. The dielectric constants of films on (100) Si and (111) InSb de...