Study of phase separation and twin defect in (111) GaAsSb by X-ray diffraction
Date Issued
2014
Date
2014
Author(s)
Lin, Yi-Heng
Abstract
Previous researches observed dual peaks in (1 1 1) GaAsSb using (3 3 3) and (1 1 1) ω-2θ HRXRD scans, and claimed it as phase separation. After that a research found existence of twinning in (1 1 1) GaAsSb by using TEM. Because twin could possibly result in dual peaks in (3 3 3) ω-2θ HRXRD scans. To confirm the phase separation in our samples, we examined the (1 1 1) ω-2θ HRXRD scans. The results show that angle differences of dual peaks varies with (1 1 1) or (3 3 3) scans, and this suggests that dual peaks observed in ω-2θ scans are due to not twin but phase separation. Then we evaluated the corresponding Sb content from both (3 3 3) and (1 1 1) ω-2θ scans. And we found that two Sb contents coincide, which allow us to affirm the existence of phase separation.
We also examined HRXRD (2 2 0) ϕ scans. Three original lattice points and three twin lattice points can be observed by (2 2 0) ϕ scans. In the sample with minimal twin showed no twin point. In the sample with bit more twin, one twin point was observed. Sample with most twin gave three twin points. Original points were broader than twin points, which is because that three kinds of twin points coincide with the original point and only one kind of twin is included in twin point. When twinning is not severe, the almost original region makes original point a sharp peak. Peaks width increases with increasing twin in samples. Moreover, asymmetric peaks were found at specific angles. We evaluated the relation between directions of twin planes, original planes and miscut, and we inferred that the tilting of twin planes is related with the direction of miscut when twinning is not severe. When twinning becomes severe, tilting of twin planes are no longer affected by surface step, which results in symmetric line shapes. We also observe that the sample with less twin gives only one twin point due to the weak diffraction intensity.
Subjects
銻砷化鎵
雙晶
相分離,x光繞射
Type
thesis
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