| Summary: | 碩士 === 國立清華大學 === 材料科學工程學系 === 92 === Thin films of Ni (1ML) and Ge (5, 10, 15, 20ML) were deposited on (100) Si substrate in the UHV chamber at room temperature, followed by ex-situ annealing at 400-800℃ for 3 hours in a separate chamber with a base pressure of 2×10-6 torr, and succeeded by characterization of scanning electron microscope (SEM), high resolution transmission electron microscope (HRTEM), transmission electron microscope (TEM) with energy dispersive X-ray spectrometry (EDX), and secondary ion mass spectrometry (SIMS).
Nickel is prevented from oxidation due to the passivation of the Ge capped layer. Therefore, Ni atoms will react with Si substrate to nucleate NiSi 2 in ex-situ experimental procedures. The retardation effect of the Ge capped layer on the formation of NiSi 2 phase was observed. The formation temperature of NiSi 2 phase is 500℃ and 580℃ for the Ge capped layer of 5ML and 20ML, respectively. The crystalographical relation, to the Si substrate, of thus-formed NiSi 2 phase is similar to that obtained from in-situ UHV deposition of a few monolayer of Ni at around 450℃. The size and density of the NiSi 2 facet bars is on the order of 400 nm x 60 nm and 1.5x108 cm-2, respectively, which are much smaller and denser than those obtained by in-situ UHV deposition at comparable temperatures.
In the system of Ge (5, 10, 15, 20 ML) / Ni (1 ML) / Si (100), NiSi 2 phase arranges along <110> direction regularly and has epitaxy with the Si substrate in the (111) planes. The Si substrate including buried NiSi 2 phase is the template with modulating lattice constants. This template can be studied in the periodic distribution of the strain field.
Keywords: scanning electron microscope, high resolution transmission electron microscope, energy dispersive X-ray spectrometry, secondary ion mass spectrometry, in-situ UHV deposition
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