Mem. Fac. Eng., Osaka City Univ., Vol. 47, pp. 21-24 (2006)

Investigation of Experimental Arrangements in X-ray Fluorescence Analysis Using

Ultra-Thin Sample Carrier

Andriy OKHRIMOVSKYY*, Takao MORIYAMA** and Kouichi TSUn***

~..-- 1!,

(Received September 29,2006)

SynopsisTo improve detection limit the Ultra-Carry was used as a sample carrier in the fluorescent X-ray

analysis. Two types of samples were prepared: Ti droplet sample and Au thin film. Measurements wereconducted in grazing exit and in conventional X-ray fluorescent conditions.

KEYWORDS: Ultra-earry, X-ray fluorescence, Signal, Background, Thin film, Droplet

1. IntroductionTo improve detection limit in X-ray fluorescence analysis of thin films, it is important to reduce

significantly the background of X-ray intensity. To achieve this goal special sample carrier may be used. Inother words, it becomes possible to decrease the dispersion of the primary X-ray from the sample carrier, bypreparing the ultra thin film of several microns as the sample carrier. In this work, we investigate theexperimental arrangements of the sample carrier and the X-ray detector to acquire the fundamental data.

2. Experimental SetupWe used a Mo X-ray tube, which was operated at an applied voltage of 30 kV and an anode

current of 20 rnA. For conventional X-ray fluorescent measurement an energy dispersive (ED)silicon drift detector was fixed in such way (Fig. 1) that primary X-ray beam direction andmeasurement direction of the fluorescent X-ray was perpendicular. The sample holder was keptvertically on the rotation stage. The incident angle of the primary X-ray and detection angle waschanged by this rotating the stage. In order to perform the grazing-exit X-ray measurement of thefluorescent X-ray (Fig. 2) the sample was fixed perpendicular to the primary X-ray beam. The detector wasplaced at the one axis transition stage which moved the detector in the direction parallel to primary X-ray. Inour experiment we used sample carrier, called the ultra-earry, (Fig. 3) produced by RIGAKU Co. 1) It is arigid plastic ring with a Mylar film stretched across and a specially formulated absorbent pad attached to thecenter. Two types of samples were considered: Au thin film and dried drop of Ti standard solution.

* Foreign Visiting Research Fellow, Department of Applied Chemistry** Researcher, RIGAKU Co.*** Associate Professor, Department of Applied Chemistry & JST-PRESTO

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Fig. 1 Experimental setup: Rotation stage

X Stage

1r

..r ·· · ·..1

Ultra ~:;~:::E::l~~~~~~~:' .

:.. ;

Fig. 2 Grazing exit X-ray measurement

Fig. 3 Sample carrier (ultra-carry) produced by RlGAKU Co.

3. Results3.1 Au: 30 nm layer prepared in vacuum-deposition chamber

As a sample, the thin film of the gold of approximately 50 om thicknesses on ultra carry (samplecarrier) was deposited by vacuum vapor deposition method.2

) Detection angle e(between the sample surfaceand detector direction) was changed from 0 degree to 360 degrees. We have measured the intensities of AuL-a and L-~ as a function of detection angle. In Fig. 4(a) the angle dependency of Au L lines intensities hasbeen shown. The background intensity for corresponding peak is displaced in Fig. 4(b). In subfigure (c) theSignallBackground (SIB) ratio is plotted. Angle dependency of the SIB ratio has almost round shape except

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greasing exit condition (8 - 0 degree or 8 - 180 degree). We will consider this case in the separatemeasurement.

a --AuLa b --Aula C -- - Au La90 90 90

7x10'Au LII 6x10' 120 eo Aulll

14 120 eo Aulll6x10~ Ul 5x10' ", '. 125x10~ 0 4x10' 10

~_,r-' _ ~..~_

Ul 4x10· 10 150/'"~r

:'--'""....,:.--..:::...,., 30 8 150 300 3x10·

_ 3x10'. ....:. "'C

10 ~ 2x10' c:: 62x10' In ' i " :::l 4

~ 1x10' c:: 1x10' ~ .' ;., _ \ 1 e 2'iii ~ -?~'~k~"Cl

c:: 0 80 0 80 0 tl 0

~1x10·

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2x10' c:: 2x10' ~ 4 .'3x10' :::l iii

IUl e 3x10'

6Ul 4x10· 210 330 c:: 8e ~ 4x10'

,2' 330

(95x10· en 106x10· III 5x10' 127x10" 2'0 300 !Xl 6x10' 240 300 14 240 300

270 270 270

Fig. 4 Au L lines as a function of take off angle (life time 50 s):a) Intensity b) Background c) Signal to Background Ratio

Grazing-exit XRF measurement was performed for gold thin film sample. Two sample arrangementswere considered. One is conventional GE-XRF, when the thin film layer is fronted to the X-ray source.Another configuration is opposite - gold film was directed out of the X-ray source. Angle dependency of AuL-a X-ray intensity (a), corresponding background intensity (b), and signal to background ratio (c) is shownin Fig. 5 for "Front" and "Back" configurations of measurement arrangement. Under grazing-exit radiationcondition, one can see the increase of intensity at the position of a certain exit angle. For "Back" sidecondition SIB ratio is quite high for negative angle. This gives us advise for optimum measurementarrangement.

.............:,~

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II)

g 2500

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II)

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Take off Angle, deg Take off Angle, deg Take off Angle, deg

Fig. 5 Au La line as a function of take off angle (life time 30s):a) Intensity b) Background c) Signal to Background Ratio

3.2 Ti: 50 J.1L ofTi solution (1.016 mglmL) in BCI (0.50 mUmL)We also have prepared Ti droplet sample. Approximately 50 ~ of Ti standard solution was dropped

on the ultra carry. After it was dried, we use this sample in XRF measurement.The detection angle ewas changed from 0 degree to 360 degrees. In the same way as for Au thin film

measurement, we have measured the intensity of Ti K-a as a function of detection angle. The angledependency for Ti K-a intensity is plotted in Fig. 6(a). In Fig. 6(b) the background intensity forcorresponding peak is shown. In subfigure (c) the SignallBackground (SIB) ratio is displayed. As for goldthin film measurement, there is no strong angle dependency of the SIB ratio.

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10'20

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~ 1200

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300

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a2.5><10'

III 2.Oxl0·

:5 1,5x10'

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-;;; 5,Oxla'e1,Ox104

C> 1,5xl0' 210

;Z 2,Oxl0'

i= 2,5><10'

Fig. 6 Ti Ka line as a function of take off angle (life time 50s):a) Intensity b) Background c) Signal to Background Ratio

In the same way as it was done for gold thin film sample, the grazing-exit measurement of thefluorescent X-ray was performed with the Ti droplet sample. The results are displayed in Fig. 6.

Under grazing-exit XRF condition, one can observe the increase of intensity at the certain exit angle.The SIB ratio for droplet sample has the similar maximum for both arrangement "Front" and "Back" mode.The difference with results of the gold thin film caused by the fact that for droplet sample, "Front" and"Back" mode actually equivalent to each other.

'. ,

-. - Front

Back :1,

..~{ ~~• .,;;, "I,.; ..

0.L,-...,.-........................,.~.........,~,-.- .......,.----,-12 -10 -8 -8 -4 -2 0 2 4 8 8

Take off Angle, deg

10 C

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6 8

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ir

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yo. ..,.

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Take off Angle, deg

4,Oxl0' a~ 3,5x10'

~ 3.0x10'

~ 2,5xl0'C

~ 2.0x10J

i 1,5Xl0'

e 'C> 1,Oxl0 .- .

~ 5,Oxlo' :' :' ". .,

i= 0,0 .t;.-;/~',-.-.......-,-.-~"'i'.. ,;;'::::;::~....,--'....:" .:;:._::;::;....-12 -10 -a -ll

Fig. 7 Ti Ka line as a function of take off angle (life time 20s):a) Intensity b) Background c) Signal to Background Ratio

4, References1) RIGAKU Co. http://www.rigaku.com/2) K. Tsuji, A. Okhrimovskyy, T. Moriyama, in abstract book of(p.215) 67-thAnnual meeting ofthe Japan

Society for Analytical Chemistry, Kitami, Hokkaido, Japan, 14-15 May (2005)

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