(Color online) (a) The J–V curves of the tox 0.61 nm TiO2 and tox 0.78 nm HfO2/TiO2 films measured at 298 K (data points), which were reproduced from Fig. 9 of Ref. 11. Lines are the quantum mechanical fitting results using the parameters mentioned in text. The dashed line corresponds to the simulated J-V curve for the 10-nm-thick TiO2 layer, having a 0.7-nm-thick HfO2 layer calculated using the given material properties. Inset figure shows the two dimensional plot of wave functions |Ψ*Ψ| as a function of distance and electron energy of the TiO2 (upper panel) and HfO2/TiO2 samples. (b) The three-dimensional plot of J differences between the standard condition and newly set conditions, read at 0.8 V as a function of me , t * and k l for the two φB o (0.75 eV and 0.90 eV) values of the HfO2/TiO2 bi-layer sample. Reprinted with permission from M. Seo, Chemistry of Materials, 22(15) (2010). Copyright © 2010, American Chemical Society.
(Color online) The variations of the dJ/dE e as a function of electron energy (E e); the applied bias voltage was 0.8 V for the single layer with a φB o of 0.75 eV and double layers with the φB o of 0.75 eV and 0.90 eV, respectively.
(Color online) J–V curves of the (a) 20-nm-thick TiO2 and (b) 20 nm TiO2/1 nm HfO2 layer, measured at various temperatures. Inset figures show the variation of the interfacial potential barrier heights, estimated from the Schottky fitting, as a function of E1/2.
(Color online) F-N tunneling fitting curves of (a) TiO2 and (b) HfO2/TiO2 thin films measured at various temperatures as a function of 1/E.
(Color online) Relative barrier height variation of TiO2 and HfO2/TiO2 film estimated from the F-N fitting as a function of measuring temperature.
(Color online) Fitting results of the experimental J–V data using the transfer-matrix method for (a) 20 nm TiO2 and (b) 1 nm HfO2/20 nm TiO2 sample. Inset table in (a) shows the parameters used for fitting and inset graph in (b) shows the leakage components of the J – V curve at 360 K.
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