| Summary: | 碩士 === 國立清華大學 === 物理系 === 101 === On this research, we investigated interface Strains for thin-film SiGe on Si substrate by using surface diffraction.
A new method is developed and employed to detect the interface information of heteroepitaxial structure.
The main concept is to choose the similar or identical diffraction condition of the thin-film system which is manufactured by similar materials and do some research about the interface/surface of the thin-film system.
By calculating the diffraction condition about the crystal of the thin-film system, both of the Si substrate and SiGe thin-film can be excited at the same time.
When the diffraction occurs, most energy of the incident beam is consumed by surface diffraction of the thin-film. Due to the penetration depth is shallow; the received signal is exact the surface information of the substrate. The diffraction condition can be controlled by tuning the concentration of Germanium doped in the thin-film. When increasing the concentration, the lattice constant increased, and vise versa.
Through analysis the intensity of incident beam、lattice constant, and diffraction condition of the sample, we can estimate the penetration depth and compare it with experimental result, by carefully tuning the x-ray penetration depth, the structural information coming from the substrate under various thickness thin-film then can easily be reached.
By slightly changing θ、φ of the sample with various thickness, we can get the information of the penetration depth、the spatial intensity distribution outside the crystal, and the intensity change of vertical electric field inside the crystal. The results are also comparable with the theory.
The tetragonal structure of SiGe thin-film due to strain was confirmed by Grazing Incident Diffraction. In addition, we also developed a method to show the interface’s effect to Bragg-surface diffraction, and give an theoretical explanation.
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