AEM ANALYSIS OF STAINLESS STEEL

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AEM ANALYSIS OF STAINLESS STEEL

R. Ogilvie

To cite this version:

R. Ogilvie. AEM ANALYSIS OF STAINLESS STEEL. Journal de Physique Colloques, 1984, 45 (C2), pp.C2-397-C2-400. �10.1051/jphyscol:1984290�. �jpa-00224005�

JOURNAL DE PHYSIQUE

Colloque C2, supplkment au n02, Tome 45, fkvrier 1984 page C2-397

AEM ANALYSIS OF STAINLESS STEEL

R.E. Ogilvie

Massachusetts Institute of TechnoZogy, Department of MateriaZs Science and Engineering, &mbridge, Massackusetts 02139, U.S.A.

Resume - On presente des analyses q u a n t i t a t i v e s de lames minces d ' a c i e r -able. Les i n t e n s i t e s X mesurees sont c o r r i g e e s des e f f e t s d'absorption,

de fluorescence e t des v a r i a t i o n s de rendement du d e t e c t e u r . Une n o u v e l l e c o r r e c t i o n de fluorescence a @t@ calculee. Une formule m o d i f i e e des equa- t i o n s de C l i f f - L o r i m e r e s t aussi presentee.

A b s t r a c t - Q u a n t i t a t i v e AEM o f t h i n f i l m s o f s t a i n l e s s s t e e l i s presented.

The X-ray data i s c o r r e c t e d f o r absorption, secondary fluorescence and d e t e c t o r e f f i c i e n c y . A new form o f the fluorescence c o r r e c t i o n has been derived. A m o d i f i e d form o f t h e C l i f f - L o r i m e r equations i s a l s o presented.

AEM a n a l y s i s o f t h i n f i l m s by the i n t e n s i t y r a t i o technique has been developed from t h e e a r l y work of Duncumb ( l ) , P h i l i b e r t and T i x i e r (2,3); however, i t was C l i f f and Lorimer (4) who developed AEM i n t o t h e powerful t o o l t h a t i s used today.

Go1 d s t e i n ( 5 ) has c l e a r l y demonstrated t h a t t h i s technique provides excel l e n t q u a n t i t a t i v e analysis. Zaluzec (6) has presented an e x c e l l e n t treatment o f t h e problems i n v o l v e d i n AEM a n a l y s i s ; however, h i s most s i g n i f i c a n t c o n t r i b u t i o n i s an equation f o r t h e i o n i z a t i o n cross-section. This paper w i l l employ many o f Zaluzec' s techniques.

I n t h i n f i l m AEM, a reasonable assumption i s made, t h a t t h e generated X-ray pro- d u c t i o n i s u n i f o r m w i t h depth. This g i v e s the f o l l o w i n g ;

where d I i i s photons/sec., C i i s t h e wt. f r a c . , ( i / e ) i s t h e electrons/sec.

i n c i d e n t on t h e specimen, NAV i s ~ v a g a d r o t number, A t h e atomic wt. Q t h e i o n i z a t i o n cross-section, w t h e f l u o r e s c e n t y i e l d , and z t h e weight o f t h e l i n e measured. I n t e g r a t i o n o f equation ( 1 ) gives t h e i n t e n s i t y measured by t h e d e t e c t o r .

Ii = - R C. ( i / e ) NAV ( Q ~ z / A ) ~ f ( X ) [l + z ( I ~ / I ~ ) ] fdTpto sec a 4Tl l

where R i s t h e s o l i d angle o f the d e t e c t o r , f ( x ) t h e absorption c o r r e c t i o n [l + c ( I S / I P ) ] t h e fluorescence c o r r e c t i o n , fd t h e e f f i c i e n c y o f t h e X-ray d e t e c t o r , T t h e counting time, to th e thickness of t h e specimen, and a t h e specimen t i l t . Therefore Ii i s the t o t a l counts o f t h e X-ray l i n e . The a b s o r p t i o n c o r r e c t i o n i s given by t h e f o l l o w i n g ;

1

-

-

where B i s t h e angle o f t h e X-ray d e t e c t o r (see Figure 1 ) .

Figure 3 i l l u s t r a t e s t h e f (X) curves f o r s t a i n l e s s s t e e l c o n t a i n i n g 0.02 phosphorus as a f u n c t i o n o f thickness.

Article published online by EDP Sciences and available at http://dx.doi.org/10.1051/jphyscol:1984290

C2-398 JOURNAL DE PHYSIQUE

The f l u o r e s c e n t c o r r e c t i o n , as d e r i v e d by P h i l i b e r t and T i x i e r (2), i m p l i e d t h a t i t c o u l d be neglected. However, Twigg and Fraser ( 7 ) reevaluated t h e i r equation and showed t h a t t h e secondary r a d i a t i o n cannot be ignored. The f l u o r e s c e n t c o r r e c t i o n has a l s o been d e r i v e d by Nockold e t a7 ( 8 ) . I n t h i s case, t h e c o r - r e c t i o n has been d e r i v e d which takes i n t o account the absorption o f the secondary r a d i a t i o n (see Figure 2). The Equation i s as f o l l o w s ;

A. Q. ( w z ) ~ r - 1 1 - exp [ ( p / p l S csc$ p t o ]

( I ~ I I ~ ) ~ = ci (u/P)J A: pto (j 7 ( 4 )

j ( (PIQ); ~ s c a ) ~

where M = ( u / p ) j csca p t o N = (p/p)S p t o Equation ( 4 ) has been solved f o r the 500 A f o i l o f NI - 5% Fe used by P h l l i b e r t and T i x i e r and c o r r e c t e d by Twigg and Fraser

.

Equation 4 1.81 10-2

P h i l i b e r t and T i x i e r 2.90 10-'

Twigg and Fraser 1.51 10-2

The f l u o r e s c e n t c o r r e c t i o n f o r s t a i n l e s s s t e e l as a f u n c t i o n o f thickness i s shown i n Figure 4.

The a n a l y s i s o f t h i n f i l m s by t h e C l i f f - L o r i m e r method and t h a t o f Zaluzec gives the f o l l o w i n g ;

blhere KAB a r e t h e C l i f f - L o r i m e r c o e f f i c i e n t s and K i = (Qwz/Ai). I t i s assumed t h a t C C i = 1, t h e r e f o r e , multicomponent systems can be analyzed. I f we know pt, we can then make an absorption and f l u o r e s c e n t c o r r e c t i o n . A m s i f i c a t i o n o f equation (5) can be done as f o l l o w s ;

F i r s t assume CA = IA/KA, CB = IB/Kb, Cc = I c C /K' where K! = ( R / ~ I T ) ( i / e ) NAV T sec a Ki Then i t e r a t e the f o l l o w i n g equations;

Using equation (6), C C i w i l l n o t always add up t o 1. I f t h e r e i s a l a r g e d i f f e r e n c e from 1, then the data i s bad.

The value of Q i s c a l c u l a t e d from t h e Zaluzec ( 6 ) equation, The values o f Q f o r C r , Fe, and Ni as a f u n c t i o n o f KV a r e i l l u s t r a t e d i n Figure 6.

The measurement o f t h e t o t a l i n t e n s i t y o f the c h a r a c t e r i s t i c l i n e s i s done by f i t t i n g a Gaussian f u n c t i o n by the method o f l e a s t squares t o 8 o f t h e channels from t h e MCA. The equations used as as f o l l o w s ;

where I, i s t h e maximum i n t e n s i t y , X has t h e value of 1 t o 8 , X. t h e peak ~ o s i t i o n , a t h e standard d e v i a t i o n , and IT t h e i n t e g r a t e d i n t e n s i t y .

X-ray measurements of 1000 A vapor deposited Cr, Fe, Ni were made using a JEOL 200X w i t h two (Si(Li))X-ray d e t e c t o r s . One d e t e c t o r i s normal t o t h e column, and t h e specimen was t i l t e d 30". The second d e t e c t o r has a 72" take-off angle. The specimen i n t h i s case was perpendicular t o t h e beam.

The i n t e g r a t e d i n t e n s i t i e s were c a l c u l a t e d from equation ( 7 ) . The Q values were c a l c u l a t e d from t h e equation of Zaluzec. The r e s u l t s of t h e s e measurements a r e given i n Table I . There may be an e r r o r i n Q , however, t h e s o l i d angle of t h e d e t e c t o r has t h e l a r g e s t e r r o r . This i s a d i f f i c u l t measurement i n t h e commercial instruments.

TABLE I

NZ

C-L Cl iff-Lorimer

Measured Calculated

K ~ r l K ~ i K ~ e / K ~ i K ~ r l K ~ e K ~ r / K ~ i K ~ e / K ~ i

1.23 1.03 1.152 1.293 1 . l 2 2

1.26 1.16

1.28 1 . l 0 1 .l41 1.269 1 . l 1 2

1.29 1.03 1 . l 3 6 1.258 1 . l 0 7

1.093 1.195 1.093

NZ N . Zaluzec

In conclusion, using t h e c a l c u l a t e d values of K a s good a s measuring them experimentally.

I want t o thank W.G. Morris of G.E. Research and Development Laboratoires f o r t h e preparation of t h e t h i n f i l m s , Larry Kolodziejski of JEOL f o r t h e d a t a on t h e J E O L 200CX, and J u l i u s Chang, a graduate s t u d e n t a t M.I.T., f o r t h e many helpful d i s c u s s i o n s on t h e equations used i n t h i s work.

References

1 . Duncumb, P., J . de Microscopic, 7 , (1968) 581.

2. P h i l i b e r t , J . and T i x i e r , R . , B r i t . J . Appl. Phy.

1

3. P h i l i b e r t , J . and T i x i e r , R. Physical Aspects of Electron Microscopy and Microbeam Analysis, ed. Siegal and Beaman, Wiley, New York, (7975).

4. C l i f f , G. and Lorimer, G . , J . Microscopy

102,

5. Goldstein, J . , I n t . t o Analytical Electron Microscopy, ed. Hren, Goldstein and Joy, Plenum Press, New York, (1979).

6. Zaluzec, N . , Ibid.

7. Twigg, M. and Fraser, H . , Microbeam Analysis, ed. Heinrich, San Francisco Press, (1 982).

8. Nockolds, C . , C l i f f , G . , Lorimer, G . , Micron fi,(1980) 325.

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z

I

Z

F i g . 1 . Absorption E f f e c t . Fig. 2. Fluorescent E f f e c t .

Fig. 3. F(x) Curves f o r S t a i n l e s s S t e e l . Fig. 4. Fluorescent Correction f o r S/S.

Fig. 5. Gaussian f i t t o Exp. d a t a . Fig. 6 . Cross Sections f o r Cr,Fe,and Ni.