EXTENDED DEFECTS AND PRECIPITATES IN IMPLANTED TiO2

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EXTENDED DEFECTS AND PRECIPITATES IN IMPLANTED TiO2

P. Thevenard, M. Guermazi

To cite this version:

P. Thevenard, M. Guermazi. EXTENDED DEFECTS AND PRECIPITATES IN IMPLANTED TiO2. Journal de Physique Colloques, 1981, 42 (C3), pp.C3-113-C3-117. �10.1051/jphyscol:1981311�.

�jpa-00220702�

EXTENDED DEFECTS AND PRECIPITATES IN IMPLANTED T i 02

P. Thevenard and M. Guermazi

Département de Physique des Matériaux, Université Claude Bernard Lyon 1, 43 Bd du 11 Novembre 1918, 69622 Villeurbanne Cedex, France

Résume.- Des monocristaux de Ti02 implantés avec des ions lourds d'énergie comprise entre 100 et 500 keV ont été observés en microscopie électronique et diffraction de rayons X. Les ions alcalins implantés établissent avec l'oxygène de la matrice des liaisons chimiques entraînant la création de Ti . Dans ce cas, les observations en microscopie électronique montrent que des défauts plans (101) sont créés dans la zone implantée. Ces défauts étendus sont décorés par des précipités qui donnent des franges de déplacement. La diffraction de rayons X permet d'identifier la nouvelle phase qui correspond à un titanate.

Par contre, lors d'implantations avec des ions Au , la présence de petits pré- cipités d'or qui était envisagée à partir de mesures d'absorption optique et de microscopie électronique, est confirmée par des mesures de diffraction de rayons X. Dans ce cas des défauts étendus et des dislocations sont observés en plus des défauts plans; ces défauts seraient liés au phénomène de pulvérisa- tion de la surface pendant l'implantation.

A b s t r a c t . - Ti02 s i n g l e c r y s t a l s implanted a t 77 K with heavy ions in the energy range (100 keV-500keV) have been observed using transmission electron microscopy (T.E.M.)and X ray d i f f r a c t i o n a t glancing incidence. Alkali ions r e a c t with oxy- gen of the l a t t i c e i n order to form chemical bonds c o r r e l a t e d with modification of the charge s t a t e of titanium (Ti ) . In t h i s c a s e , T.E.M. observations show that planar defects (101) type are created in the implanted l a y e r . These exten- ded defects are decorated by p r e c i p i t a t e s which give displacement f r i n g e s . The formation of t i t a n a t e considered a f t e r T.E.M. experiments i s confirmed by X ray d i f f r a c t i o n . On the opposite s i d e , m e t a l l i c ions of high e l e c t r o n e g a t i v i t y such as Au+implanted in Ti02 form small m e t a l l i c c l u s t e r s . The presence of gold p r e c i p i t a t e s which have been considered a f t e r o p t i c a l and T.E.M. measurements i s confirmed by X ray d i f f r a c t i o n a n a l y s i s . More d i s l o c a t i o n s and extended de- fects are observed in addition to planar d e f e c t s ; they can be due to s p u t t e r i n g effects during implantation.

1 . I n t r o d u c t i o n . - C h e m i c a l i m p l a n t a t i o n e f f e c t s i n t i t a n i u m d i o x y d e h a v e b e e n r e v e a l e d by p r o t o n a n d d e u t e r o n i m p l a n t a t i o n s / I , 2 / . T h e s e p a r t i c l e s e s t a b l i s h c h e m i c a l b o n d s w i t h o x y g e n of t h e h o s t m a t r i x a n d a c o n c o m i t a n t c r e a t i o n o f i n t r i n s i c d e f e c t s T i i s i n d u c e d by t h e c h e - m i c a l r e a c t i o n s . S i m i l a r e f f e c t s o c c u r i n T i O - i m p l a n t e d w i t h m e t a l l i c i o n s M h a v i n g e l e c t r o n e g a t i v i t y l o w e r t h a n t i t a n i u m o n e : a l k a l i i o n s +

f o r e x a m p l e g i v e M-O b o n d and T i / 3 / . T h e s e c h e m i c a l e f f e c t s a r e n o t o b s e r v e d w i t h m e t a l l i c i o n s s u c h a s Au h a v i n g e l e c t r o n e g a t i v i t y h i g h e r t h a n t i t a n i u m o n e . T a k i n g i n t o a c c o u n t o f t h e s e c h e m i c a l e f f e c t s , new p h a s e f o r m a t i o n c a n b e c o n s i d e r e d i n h e a v i l y i m p l a n t e d s a m p l e s . I n o r - d e r t o i d e n t i f y t h e s e new p h a s e s t r a n s m i s s i o n e l e c t r o n m i c r o s c o p y a n d X r a y d i f f r a c t i o n a t g l a n c i n g i n c i d e n c e h a v e b e e n p e r f o r m e d i n T i 02

Article published online by EDP Sciences and available at http://dx.doi.org/10.1051/jphyscol:1981311

c3- 114 JOURNAL DE PHYSIQUE

single crystals implanted with potassium, rubidium and gold ions.

2. Experimental procedure.- Rutile single crystals were obtained from

"DJEVA". The impurity content was lower than 2 0 0 p.p.m, (principally silicon and chromium). Single crystals were polished with the c-axis perpendicular to the faces, the target areas being 1.5 cm2 and the sample thickness of the order of 0 . 1 cm. The implantAtions were perfor- med at 77 iZ using either a "Danfysik" implantor or "Van de Graaf" ma- chine. The energy was 4 5 0 keV for potassium, 2 MeV for rubidium and

3 0 0 keV for gold. The bombardment target area was 1 cm2 and the particle

-2 -1 flux 1 0 1 3 ions. cm .s

.

During thermal annealings, the samples were placed in a platinium box. The implanted crystals were annealed for 3 0 minutes at a given temperature.

A transmission electron microscope "Philips EM 3 0 0 " fitted with a goniometric stage was used to observed implanted samples. After im- plantation the implanted targets were thinned using a 5 keV Ar beam 4-

incident at 15'. Thinning was carried out from the unimplanted side until a hole was obtained. A thickness corresponding to the mean pro- jected range of the particles was then removed from the implanted side.

X ray diffraction patterns were obtained in a G.E.C. X ray texture camera, the samples being placed at a glancing incidence of 30'.

supplementary spots

+ 17

Fig. 1.- Transmission electron microscopy of Ti02 implanted with 450 keV K (10 ions.cm

a) Displacement fringe contrast observed in dark field associated to precipitates b) Diffraction pattern from precipitate

projected range of the particles is 3300; and the range straggling 7 0 0

g .

T.E.M. observations on as implanted samples are'performed at 300 K.

Planar defects of type ( 7 0 1 ) are observed in the implanted area: figure 1 a. In addition the diffraction pattern obtained on the planar defects exhibits additionnal spots which are due to precipitates: figure lb.

The dark field image associated with these extra spots reveal that the precipitates are localized following the planar defects; figure la. The interference fringes are typical of displacement fringes with interfringe

0

distances about 1 0 0 A. These T.E.M.observations are adequate to show the existence of precipitates, but the identification of the precipitates phase is difficult using the diffraction pattern. In order to charac- terize the new phase X ray diffraction at glancing incidence is a sui- table technique particularly in implanted samples. As rubidium ions present similar chemical effects as potassium implanted in Ti02, X ray diffraction has been performed in Ti02 implanted with rubidium.

3.2. Rubidium implanted in Ti02.- The samples are implanted at 7 7 K

-

with 1017 ions .cm of 2 MeV rubidium and annealed at 8 0 0 K. The mean

0

penetration depth of the particles is 7 1 0 0 A and the range straggling is 3 8 0 0 A. T.E.M.observations of the implanted region show that planar defects and precipitates are created as in potassium implanted samples:

figure 2.

a ^a

p

'

F ^p

. a

0 . 0 3

x w a

i i o , •

l

Pig. 2.- T.E.N. o f Ti02 implanted with 300 keV ~ b + ions.cm-2) a) dark field

b) diffraction pattern from precipitates

c3- 116 JOURNAL DE PHYSIQUE

The diffraction lines observed on X ray diffraction pattern on figure 3 are due to the precipitates. Using Wallace's method 4 the diffraction lines are identified as being due to precipitates of Rb2 Ti03 and then indexed.

R b2Ti

o3

Fig. 3.- X ray diffraction pattern at glancing incidence

(30") of ~ i 0 2 irnplanted-yith 2 MeV ~ b + ( 1 0 ' ~ ions.cm ₎

Fig. 3

3.3 Ggid-&gplanted in Ti03.- Ti02 single crystals are implanted with - 2

1.45 x 1 0 1 7 ions-cm of 3 0 0 keV gold particles. The mean penetration depth is 5 2 0 and the range straggling 1 3 0

i.

Fig. 4.- X ray diffraction pattern at glan- cing incidence (30°) of Ti02 implanted with 1.45 x 1017 ions.cm2 of 300 keV A$.

Fig. 4

The precipitation of small metallic aggregates of gold has been considered in gold implanted samples by means of optical absorption measurements and T.E.M observations /5,6/. In order to characterize the aggregates, X ray diffraction analysis is performed on these samples.

Figure 4 shows the diffraction pattern of a gold implanted sample. Seve- ral diffraction lines due to precipitates are detected and identified.

They correspond to small metallic precipitates of gold. In these experi- ments the implanted layer is strongly perturbed as shown on figure 5.

This is due to the high concentration of gold particles in the implan- ted area and to the sputtering of the target surface during implanta- tion which can lead to the formation of non stoichiometric titanium oxyde.

4. Conclusion.- Ion implantation intitaniumdioxyde can lead to the formation of new phases. Transmission electron microscopy shows that the new phase precipitation is correlated with the existence of planar extended defects of (i01) type. In addition, X ray diffraction at glan- cing incidence allows to characterize these new phases: mixte compounds such as titanated in Ti02 implanted with alkali ions, or extrinsic clus- ters of metallicparticlesin Ti02 implanted with metallic ions havinq electronegativity higher than titanium one such as gold.

References

/1/ Siskind, B., Gruen, D.PI. and Varma, R., J. Vac. Sci. Technol.

14 ( 1 9 7 7 ) 5 3 7 -

/2/ Guermazi, M., Thevenard, P., Paisant, P., Blanchin, PI.G. and Dupuy, C.H.S., Radiat. Effects

37

/3/ Guermazi M., Thevenard, P., Treilleux, M. and Dupuy, C.H.S,

?,later. Res. Bull.

15

/4/ Wallace, C.A. and Ward, R.C.C., J. Appl. Crystallogr.

8

/5/ Guermazi, M., Thevenard, P., Dupin, J.P. and Dupuy, C.H.S.

Radiat. Effects

49

/6/ Guermazi, M., Thevenard, P., Dupin, J.P. and Dupuy, C.H.S.

Nucl. Instrun. Methods ( 1 9 8 1 ) to be published