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Local structure analysis of rewritable optical media during phase change

  • Only SPring-8

Inquiry number

SOL-0000001053

Beamline

BL01B1 (XAFS I)

Scientific keywords

A. Sample category inorganic material
B. Sample category (detail) metal, alloy, semiconductor, solid-state crystal, amorphous, glass, inorganic thin film
C. Technique absorption and its secondary process
D. Technique (detail) XAFS, EXAFS, XANES
E. Particular condition polarization (linear), room temperature
F. Photon energy X-ray (4-40 keV)
G. Target information chemical bonding, local structure, structural change, function and structure, function, phase transition

Industrial keywords

level 1---Application area storage device
level 2---Target CD-R、DVD
level 3---Target (detail)
level 4---Obtainable information structure of non-crystalline material, interatomic distance, crystal structure, local structure, electronic state
level 5---Technique XAFS

Classification

A80.12 semiconductor, A80.30 inorganic material, M40.10 XAFS

Body text

In this solution, EXAFS method was applied to Ge2Sb2Te5 thin film (20 nm thickness), the material of rewritable optical media, to analyze local structural change during phase change. EXAFS spectra of the sample in crystalline and amorphous phase were measured at Ge, Sb and Te K-edge. The EXAFS method is a powerful technique to study local structure (distance, coordination number, species of neighbor atoms) of selected elements both in crystalline states and in non-crystalline states. Figure 1 shows radial structure function of Te atom after Fourier transform of EXAFS spectra. Simultaneous analysis of EXAFS data set at 3 edges revealed that the fast rewritable mechanism is due to the change in position of Ge atom in rigid building blocks.

Fig. 1 Radial structure function for Te atom in crystallized and amorphized samples.

Fig. 2 Fragments of the local structure of GST around Ge atoms in the crystalline (left)
and amorphous (right) states (red: Ga).

[ A. V. Kolobov, P. Fons, A. I. Frenkel, A. L. Ankudinov, J. Tominaga, T. Uruga, Nature Materials 3, 703-708 (2004), Fig. 1(c), 5,
©2004 Nature Publishing Group ]

Source of the figure

Original paper/Journal article

Journal title

Nature Materials, 3, 703 (2004)

Figure No.

1(c), 5

Technique

XAFS spectra of thin film samples having a high density of core-hole atoms are obtained by measuring Auger electron yield from excited atoms as a function of x-ray energy. A conversion electron yield (CEY) detector is used for this measurement. The CEY XAFS mode is successfully applied for the 0.1 nm thick film samples. Acquisition time per spectrum is 1-2 hr.

Source of the figure

Private communication/others

Description

講習会プレゼン資料

Required time for experimental setup

4 hour(s)

Instruments

Instrument Purpose Performance
XAFS Measurement System Measurement of XAFS spectra 3.8-113 keV
CEY Detector Measurement of XAFS spectra of dense thin film thickness > 0.5 nm

References

Document name
A. Kolobov et al., Nature Materials, 3, 703 (2004).

Related experimental techniques

Questionnaire

The measurement was possible only in SPring-8. Impossible or very difficult in other facilities.
This solution is an application of a main instrument of the beamline.

Ease of measurement

Middle

Ease of analysis

With a great skill

How many shifts were needed for taking whole data in the figure?

Less than one shift

Last modified 2022-05-06 15:21