XRD scans of PTO grown on SRO/STO. The PTO film thickness was (from bottom to top) 7, 14, 24, and , respectively. The diffractograms have been displaced along the intensity axis for clarity. Bold lines show measured data, while the fine lines are fits obtained from the idealized structure.
The PTO -axis lattice constant, as obtained from fits to the XRD data, plotted vs film thickness. Films thicker than show a fixed out-of-plane lattice constant, close to the bulk value, while thinner films show a lattice constant which decreases monotonically with the film thickness. No significant difference is seen for films deposited on different substrates or grown at different substrate temperatures. The error bars, shown for films grown on Nb:STO substrates only, indicate the uncertainty in the fitted values. For films thicker than , the error bars are smaller than the symbols.
Pole figure of the (113) PTO and (103) STO diffraction peaks for a thick sample grown on SRO/STO. The solid circles identify the region of measurement. The (113) PTO peaks appear at 45° with respect to the (103) STO peaks, which testifies to the cube on cube epitaxy.
Reciprocal space map of (103) diffraction peaks for a thick PTO film grown on SRO/STO. The PTO, SRO, and STO peaks all have the same in-plane lattice constant.
AFM images of PTO films grown on SRO/STO. The film thicknesses were (a) , (b) , (c) , (d) , (e) , and (f) . The -range of the linear grayscale is for all images. Clear step-and-terrace structures are observed for the thinnest films, gradually disappearing for thicker films.
Measured capacitance of Pt/PTO/Nb:STO capacitors (filled circles) and Pt/PTO/SRO capacitors (open circles) with area. The error bars are the standard deviations of measurements on different capacitors. The solid line is a fit to the data for films thicker than , imposing an inverse thickness dependence. The dotted line is the capacitance calculated for an MIM model and the dash-dotted line is the capacitance calculated for an MIS model. The inset shows the inverse capacitance for films with an SRO bottom electrode vs. film thickness. The linear fit gives a negative intercept corresponding to .
The -axis lattice constant for thick films grown on Nb:STO (filled circles) and SRO (open circles) as a function of growth temperature. The error bars, shown for films grown on Nb:STO substrates only, indicate the uncertainty in the fitted values.
scan of a thick PTO film grown on Nb:STO substrate at . The peaks from PTO and STO is seen along with an unidentified impurity phase at .
Peak intensity ratio of the Pb and Ti emission from XPS measurements on PTO films on Nb:STO substrates, as a function of growth temperature. The relative Pb content is seen to decrease with increasing temperature.
Hysteresis loops (thick lines) and switching currents (thin lines) measured on PTO films with SRO bottom electrodes. The film growth temperatures were (a) , (b) , (c) , (d) , (e) , and (f) .
Switchable polarization as a function of film growth temperature. A marked decrease in the polarization is seen with increasing growth temperature. The error bars are the standard deviations of measurements on different capacitors.
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