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We demonstrate a high-quality La2O3 layer on germanium (Ge) as an epitaxial high-k-gate-insulator, where there is an atomic-arrangement matching condition between La2O3(001) and Ge(111). Structural analyses reveal that (001)-oriented La2O3 layers were grown epitaxially only when we used Ge(111) despite low growth temperatures less than 300 °C. The permittivity (k) of the La2O3 layer is roughly estimated to be ~19 from capacitance-voltage (C-V) analyses in Au/La2O3/Ge structures after post-metallization-annealing treatments, although the C-V curve indicates the presence of carrier traps near the interface. By using X-ray photoelectron spectroscopy analyses, we find that only Ge–O–La bonds are formed at the interface, and the thickness of the equivalent interfacial Ge oxide layer is much smaller than that of GeO2 monolayer. We discuss a model of the interfacial structure between La2O3 and Ge(111) and comment on the C-V characteristics. [ABSTRACT FROM AUTHOR]

Oxygen bonding in La-silicate film with compositional gradient has been characterized by x-ray photoelectron spectroscopy. Based on an analytical model of bridging and nonbridging oxygen, the O 1s spectra arising from La-silicate layer have been deconvoluted with compositionally dependent parameters. For a composition ratio of 1:1 for SiO2 and LaO1.5 on the surface of the La-silicate layer, negative binding energy shifts of 0.35 and 0.10 eV for bridging and nonbridging oxygen, respectively, have been found to well interpret the angle-resolved spectra. The method has also been applied to characterize the temperature dependence of interface reactions at La2O3/Si with in situ processed Pt electrode. SiO4 molecules combined with bridging and nonbridging oxygen atoms have been found to form by high temperature annealing. The thickness of the silicate layer of 0.4 nm at as-deposited state has been found grow up to 2.8 nm after 500 °C annealing. From rough estimation, it has been revealed that 10% of the newly created bridging oxygen atoms by annealing are incorporated into SiO4 network which contain also nonbridging oxygen atoms. [ABSTRACT FROM AUTHOR]

The chemical states of Fe and Pt in in situ annealed L10 structured FePt nanodots formed by self-assembled nanodot deposition method have been systematically investigated by angle resolved x-ray photoelectron spectroscopy. From the Fe3p and the Pt4f core level x-ray photoelectron (XP) spectra, it is evident that both the Fe and Pt of the nanodots were oxidized in the as-grown state. After the in situ annealing under high vacuum, a peak corresponding to metallic Fe begins to appear, and subsequently the metallic peak fraction increased with the increase in the annealing temperature. In line with this, the peak fraction of the respective oxides is drastically decreased. Irrespective of the annealing temperatures, it is inferred from the intensity of the XP spectrum that the Fe atom of the FePt nanodots is highly prone to oxidation than the Pt atom. Nevertheless, the valence band spectra of the as-grown FePt nanodot film clearly depict the presence of metallic Fe–Pt alloy. We would like to explain the results of the core level and valence band XP spectra as follows: only the peripheral Fe and Pt atoms of the as-formed FePt nanodots are bonded to the oxygen of the cosputtered SiO2 matrix, whereas the metallic core of the as-formed FePt nanodots is always preserved. The very good vacuum ambient during postannealing highly promotes the dissociation of oxygen from the metal oxides via reduction reaction. This results into an increase in the fraction of metallic Fe and Pt at the periphery of FePt nanodots and the formation of high quality SiO2 matrix after annealing. Similar results were also observed for the monatomic W as well as Pt nanodots embedded in SiO2 matrix. Hence, this simple, rather effective method of in situ annealing of metal dots dispersed in an insulating matrix can be readily employed in the fabrication of high-density nanodot memory devices. [ABSTRACT FROM AUTHOR]