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(a) C-V and (b) I-V characteristics of Au/GeO2/Ge and Al/GeO2/Ge capacitors.
Cross-sectional TEM images of (a) Au/GeO2/Ge and (b) Al/GeO2/Ge stacks.
Depth profiles of (a) Au/GeO2/Ge and (b) Al/GeO2/Ge stacks obtained by XPS with Ar+ ion sputtering. Horizontal axis (sputtering time) indicates the depth of the stacked structure on the basis of metal-electrode surface. It is noted that the components of GeO2 and Ge0 in the Ge3d spectra and Al2O3 and Al0 in the Al2p spectra are deconvoluted from the measured spectra. The photoelectron take-off angle (θ) was 45°.
(a) Al 2p and (b) Ge 3d fine spectra of the Al-electrode surface (sputtering time: 3 min) and the Al/GeO2 interface (sputtering time: 10 min) in the Al/GeO2/Ge stack obtained by XPS with Ar+ ion sputtering. The sputtering time corresponds to the depth of the sample as shown in Fig. 3(b) . Vertical axis is normalized by the maximum and minimum intensities of photoelectron counts.
Schematic illustrations of the interfacial reactions between Al-gate electrode and GeO2 dielectric.
(a) Ge2p3/2 spectra of Au/GeO2/Ge, Al/GeO2/Ge, Al/Ge3N4/GeO2/Ge, and Al/Al2O3/GeO2/Ge stacks obtained by HAXPES. (b) Expansion of Ge0 region in Ge2p3/2 spectra of Al-gate stack samples. Vertical axis is normalized by Ge0 (Ge-Ge) peak. The photoelectron take-off angle (θ) of HAXPES is 88°.
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