Photon Factory Activity Report 2005 #23 Part B (2006)
Crystallography

15C/ 2006G041

Observation of Interference Fringes Induced by Lattice Distortion in Resonant
Scattering X-ray Topography IIRiichirou NEGISHI*1, Tomoe FUKAMACHI1, Masami YOSHIZAWA1, Kenji HIRANO1,Toshiyuki TANAKA1, Tsuyoshi OBA1,Keiichi, HIRANO2, Takaaki KAWAMURA3
1
Saitama Institute of Technology, 1690 Fusaiji, Fukaya, Saitama 369-0293, Japan
2
Institute of Material Structure Science, KEK-PF, Oho, Tukuba, Ibaraki 305-0801, Japan
3
University of Yamanashi, 4-4-37 Takeda, Kofu, Yamanashi 400-8510, Japan
We previously reported on topographs in which interference
fringes by lattice distortion were observed when the Fourier
coefficient of the imaginary part of X-ray polarizability χ hi
was zero for GaAs 200 reflection [1]. In this paper, we report on
the contrast variation of the fringe for GaAs 200 reflection bychanging the Bragg angle or the X-ray energy.
The experiment was carried out at BL-15C in KEK-PF. The
X-rays from synchrotron radiation were monochromated by a Si
111 double-crystal and a GaAs 200 monochromator. The
resultant topographic images are shown in Figs.1 and 2. Fig.1
shows an image recorded on the nuclear plate when X-ray
energy is 9eV below the Ga K-absorption edge (10368eV)
satisfying the condition χ hi = 0 . Figs.2 (a) and (b) show theimages when X-ray energy is 4eV and 1eV below the Ga
K-absorption edge, respectively. The darker contrast
corresponds to the higher X-ray
intensity. The reciprocal lattice vector his in the upward direction. Figs. 1(a) and(b) are the images for negative andpositive ∆θ , respectively, where ∆θ isthe deviation angle from the Braggcondition. Figs. 2(a) and (b) are theimages for negative∆θ. The defectimages A and B are observed in Figs.1and 2(a), but the defect A is not visible
in Fig.2 (b).
The interference fringes are observed
clearly in Fig.1 (a) when ∆θ is negative.
The interference fringe α is observed in
the dark band area, and the fringe spacing
increases as the distance from A increases.
The interference fringe β overlaps withthe lower left of the defect B, and thefringe spacing increases as the distancefrom B increases. In Fig.1 (b), a dark band
region is observed around the defect A. In
the dark region, the interference fringe α′
is observed in the opposite side of α, butno fringe is observed in the opposite sideof α or β in Fig.1 (a). The fringe
spacing of α′ also increases as the distancefrom the defect A increases. Theinterference fringes α and β are alsoobserved in Fig.2 (a), although thecontrasts are weaker than those in Fig.1 (a).

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In Fig. 2(b), such fringes are scarcely observed. The contrast of
the interference fringe becomes weak when ¨χhi¨ increases fromzero as the X-ray energy becomes closer to the absorption edge
from 9eV below it.
As shown in Fig. 1, the interference fringes are clearlyobserved in the peculiar condition χ hi = 0 . The fringe area isrestricted only in one side of each defect when ∆θ is changed
and the fringe spacing increases as the distance from the defectincreases, which implies that the fringes are induced by thelattice distortion around the defect. Thus, it is noted that theinterference fringes at χ hi = 0 are quite useful for elucidating
lattice distortion structures.
[1] R. Negishi et al., KEK Progress Report, #22, 233(2005).
*
negishi@sit.ac.jp