Photon Factory Activity Report 2004 #22 Part B (2005)
Materials Science

16A/2002S003

X-ray fluorescence imaging of combinatorial Pt-Ta-Ru alloy library
Mari MIZUSAWA, Parhat AHMET, Toyohiro CHIKYOW and Kenji SAKURAI*
National Institute for Materials Science, Sengen, Tsukuba, Ibaraki 305-0047, Japan
Introduction
Combinatorial synthesis is a modern technique that has
been applied to efficiently seek out promising candidates
for specific materials applications [1].
Using thistechnique, various samples are prepared under very
different conditions as an array on a single substrate. Thetechnique requires efficient methods of characterization.
In this study, X-ray fluorescence imaging was applied toquickly observe the chemical composition of an
inhomogeneous Pt-Ta-Ru ternary alloy system.
Experimental
Figure 1 shows a sketch of the present sample, which
was prepared via a combinatorial method. Metallic Pt, Ta
and Ru are evaporated by using an ion-beam system sothat the chemical composition is graded on a Si(100)substrate. The layer thickness is designed to be ca. 30 nm.
Details of the instrumentation of the present X-ray
fluorescence microscope have been described elsewhere[2]. The sample was broken into 3 parts, and the viewing
area was set at 13mm × 13mm in order to observe
substrate A, which includes the ternary alloy area. The
typical exposure time for one image was 10 sec.

Results and Discussion
Figure 2 shows the X-ray images obtained when theprimary photon energy is 11600eV (above the Pt LIIIedge), 11400eV (below the Pt L III edge but above the Ta
LIII edge), and 9600eV (below the Ta LIII edge). At
11600eV, both Ta and Pt are excited, but only Ta X-ray
fluorescence is seen at 11400 eV. One can determine theatomic ratio of Pt and Ta at each point on the substrate byanalyzing those images. Drawing line profiles, as shownin Fig.3, is sometimes useful for evaluating the gradation.
Unfortunately, it was difficult to observe X-ray
fluorescence from Ru, because both the K (22117eV) andL absorption edges (2800~3200eV) are beyond the rangeof the present system. On the other hand, 2D X-ray
diffraction imaging [3] is extremely important for
obtaining specific materials parameters from such a
combinatorial library. Further studies are under way.
The authors would like to thank Drs. H. Sawa, Y.
Wakabayashi, Y. Uchida, for their assistance and advice
during the experiment..
References[1] P. Ahmet, Y-Z. Yoo, K.Hasegawa, H. Koinuma and T.
Chikyow; Appl. Phys. A79, 837 (2004).
[2] K.Sakurai and H.Eba, Anal. Chem., 75, 355 (2003);
K.Sakurai and M.Mizusawa, Nanotechnology, 15, S428
(2004).
[3] K.Sakurai and M.Mizusawa, Photon Factory Activity
Report 2003, #21, p.260 (2004).
*sakurai@yuhgiri.nims.go.jp

Figure 1 Schematic view of combinatorial Pt-Ta-Ru
ternary alloy thin film. The preparation is such that
gradation of the chemical composition depends on thelocation on the substrate.
11600 eV

11400 eV

9600 eV Figure 2 X-ray images obtainedat different incident X-ray photon
energies, 11600eV, 11400eV,and 9600eV, which give images
for both Pt and Ta, only Ta, andjust scattering, respectively.

Figure 3 Line profiles along X-X' and Y-Y' (as indicatedin Fig.1). Chemical composition grading is evaluated bythose data.

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