THERMAL PHONON TRANSPORT STUDY OF THE DEFECTS CREATED IN QUARTZ SINGLE CRYSTALS BY DIFFERENT IRRADIATIONS (γ RAYS, ELECTRONS, NEUTRONS)

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THERMAL PHONON TRANSPORT STUDY OF THE DEFECTS CREATED IN QUARTZ SINGLE

CRYSTALS BY DIFFERENT IRRADIATIONS (γ RAYS, ELECTRONS, NEUTRONS)

A. de Goër, M. Locatelli, C. Laermans

To cite this version:

A. de Goër, M. Locatelli, C. Laermans. THERMAL PHONON TRANSPORT STUDY OF THE DEFECTS CREATED IN QUARTZ SINGLE CRYSTALS BY DIFFERENT IRRADIATIONS (γ RAYS, ELECTRONS, NEUTRONS). Journal de Physique Colloques, 1981, 42 (C6), pp.C6-78-C6-80.

�10.1051/jphyscol:1981624�. �jpa-00221325�

JOURNAL DE PHYSIQUE

CoZZoque C6, suppZ6ment au nO1 2, Tome 42, &cembre 1981 page C6-78

THERMAL PHONON TRANSPORT STUDY OF THE DEFECTS CREATED I N QUARTZ S I N G L E CRYSTALS BY DIFFERENT IRRADIATIONS (Y RAYS, ELECTRONS, NEUTRONS)

A.M. de Go&, M. L o c a t e l l i and C. ~ a e r m a n s *

Service Basses Te'emp&ratures, C. E. N. G., 85X, 38041 GrenobZe Cedex, France

* ~ a b . Vaste Stof- en Hoge Drmkfysika, K. U. Leuven, CeZestijnenZaan 2000, 3030 Leuven, Be Zgiuni

Abstract.- Thermal c o n d u c t i v i t y measurements have been c a r r i e d o u t between 8 0 mK _{and 30 K} i n q u a r t z a f t e r y, e l e c t r o n and n e u t r o n i r r a d i a t i o n a t d i f f e - r e n t doses. A l l t h e samples were n a t u r a l q u a r t z of t h e same o r i g i n , i n o r d e r t o r u l e o u t t h e e f f e c t s of d i f f e r e n t sample s t a t e . E l e c t r o n and n e u t r o n s c a u s e an a d d i t i o n a l phonon s c a t t e r i n g which, below 1 K , can be explained by t h e pre- sence of t u n n e l i n g s t a t e s s i m i l a r a s i n amorphous s o l i d s b u t which i s very d i f f e r e n t above lK, i n d i c a t i n g t h e d i f f e r e n t o r i g i n of t h e g l a s s y "plateau".

y - i r r a d i a t i o n does n o t induce a d e t e c t a b l e number of t u n n e l i n g s t a t e s .

I n t r o d u c t i o n . - I n o r d e r t o come t o a b e t t e r understanding of t h e microscopic o r i g i n of t h e t u n n e l i n g s t a t e s i n amorphous s o l i d s some a t t e n t i o n has been d i r e c t e d t o cry- s t a l l i n e q u a r t z which i s l o c a l l y d i s o r d e r e d by high energy n e u t r o n s and e l e c t r o n s , showing s i m i l a r low temperature dynamical p r o p e r t i e s 1-4

.

and i n 6 a magnetic f i e l d have been c a r r i e d o u t p r e v i o u s l y and t h e number of t u n n e l i n g s t a t e s and t h e i r coupling c o n s t a n t t o phonons h a s been determined 2

.

Experimental re*.- The thermal c o n d u c t i v i t y K measurements have been c a r r i e d o u t between 8 0 mK and 3 0 K and t h e r e s u l t s a r e g i v e n i n f i g . 1 (a and b ) . P a r t of t h e d a t a have been r e p o r t e d b e f o r e 3 7 6 . A l l a r e n a t u r a l B r a z i l i a n q u a r t z r o d s of t h e same o r i g i n , 3mm i n diameter and about 8mm i n l e n g t h . The v a l u e of K a t t h e maxi- mum, f o r t h e v i r g i n sample, i s s i m i l a r t o t h a t found i n e a r l i e r measurements t a k e n i n t o account t h e s m a l l e r dimensions of t h e p r e s e n t samples. Between 0.4 and 3K a T 3 behavior t y p i c a l f o r boundary s c a t t e r i n g i s found and t h e d a t a a g r e e w e l l w i t h t h e v a l u e s f o r t h e boundary s c a t t e r i n g c a l c u l a t e d from t h e e l a s t i c c o n s t a n t s (Casimir l i m l t ) . This a l s o i m p l i e s t h a t we f i n d no evidence f o r t h e presence of i n c l u s i o n s a s observed b e f o r e i n s y n t h e t i c samples4. Using y - i r r a d i a t i o n , t h e e f f e c t of p u r e l y i o n i z i n g i r r a d i a t i o n was measured ( u n t i l now o n l y measured above 1K). The two d i f f e -

6 8

r e n t doses 5 . 9 x 10 and 2.1 x 10 Roentgen g i v e t h e same r e s u l t , s o t h a t s a t u r a t i o n i s a l r e a d y achieved. The thermal c o n d u c t i v i t y i s l i t t l e a f f e c t e d above 1K and n o t a t Article published online by EDP Sciences and available at http://dx.doi.org/10.1051/jphyscol:1981624

.g. 1. Thermal c o n d u c t i v i t y a s a f u n c t i o n of temperature: V: u n i r r a d i a t e d sample, El and E2: e l e c t r o n i r r a d i a t e d ; N],N2,N3: n e u t r o n i r r a d i a t e d ; G: g l a s s sample. I r r a d i a t i o n dose: s e e t a b l e 1. S o l i d l i n e s a r e c a l c u l a t e d t o f l t t h e experiments.

a l l below lK, were t h e d a t a f o r t h e v i r g i n sample a r e reproduced.

E l e c t r o n and n e u t r o n i r r a d i a t i o n induce i n t h e whole temperature range a n a d d i t i o n - n a l phonon s c a t t e r i n g which i n c r e a s e s w i t h i n c r e a s i n g dose, and i s remarkably d i f f e - r e n t above 1K b u t shows s i m u l a r i t i e s below 1K. Above lK, i n t h e n e u t r o n i r r a d i a t e d samples, a p l a t e a u appears, s i m i l a r t o g l a s s e s , a s a l r e a d y known 8 .

Discus.qion.- A computer f i t was made u s i n g t h e f u l l Debye e x p r e s s i o n f o r t h e t h e r - mal c o n d u c t i v i t y , s t a r t i n g from a f i t f o r t h e v i r g i n sample and i n t r o d u c i n g a n ad- d i t i o n n a l s c a t t e r i n g mechanism t o account f o r t h e r a d i a t i o n damage: tcl = Gw and an i n c r e a s e of t h e p o i n t d e f e c t term A, t h e Casimir term being k e p t a t t h e c a l c u l a t e d v a l u e . The r e s u l t s a r e r e p o r t e d i n t a b l e 1 and i n f i g . 1 (some only p a r t l y f o r c l a - r i t y ) . More d e t a i l s about t h e f i t t i n g procedure a r e g i v e n i n a previous paper 3

.

A t t h e v e r y lowest temperatures t h e f i t u n d e r e s t i m a t e s t h e v a l u e of t h e thermal con- d u c t i v i t y a s w e l l i n t h e v i r g i n sample a s i n t h e i r r a d i a t e d samples ( s e e a l s o f i g . 1

?n t h e p r e v i o u s paper 3 ). This e f f e c t i s u s u a l l y a t t r i b u t e d t o s p e c u l a r r e f l e c t i o n and w i l l n o t b e d i s c u s s e d i n more d e t a i l here. Apart from t h i s s m a l l d e p a r t u r e s i t was found t h a t i n t h e c a s e of t h e e l e c t r o n i t r a d i a t e d samples t h e expected Rayleigh s c a t t e r i n g , due t o p o i n t d e f e c t s a l o n e , can n o t e x p l a i n t h e d a t a and t h a t a c o n s t a n t

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T a b l e I

+ e l e c t r o n energy 2 MeV; n e u t r o n s w i t h e n e r g y > 0.1 MeV; n e u t r o n d o s e Ng i s p r e - l i m i n a r y

+ noR2 = 1.2 x l o 8 erg/cm3 i s a c a l c u l a t e d mean v a l u e .

d e n s i t y of s t a t e s of TLS(two l e v e l s t a t e s ) s i m i l a r a s i n g l a s s e s c a n f i t t h e r e - s u l t s 3 . From G a v a l u e f o r t h e c o u p l i n g s t r e n g h t n o ~ 2 of t h e TLS w i t h t h e t h e r m a l phonons i s o b t a i n e d ( s e e t a b l e 1). F o r t h e n e u t r o n i r r a d i a t e d samples a s i m i l a r f i t was c a r r i e d o u t b u t o n l y f o r t h e t e m p e r a t u r e s below 1K s i n c e t h e " p l a t e a u " i n g l a s - s e s i s n o t y e t u n d e r s t o o d . A c o n s t a n t d e n s i t y o f s t a t e s of TLS c a n , a l s o i n t h i s c a s e , f i t t h e d a t a . T h i s i s i n agreement w i t h e a r l i e r f i n d i n g s which show t h a t TLS a r e p r e s e n t i n n e u t r o n i r r a d i a t e d For t h e y - i r r a d i a t e d samples no e v i - dence f o r t h e p r e s e n c e of TLS was found up t o s a t u r a t i n g d o s e which p u t s a n upper l i m f t t o t h e number p o s s i b l y p r e s e n t ( s e e t a b l e 1 ) .

It i s s u r p r i s i n g t h a t i n s p i t e o f t h e v e r y d i f f e r e n t damaging p r o c e s s e s , b o t h n e u t r o n and e l e c t r o n i r r a d i a t i o n i n d u c e TLS. Indeed n e u t r o n s c a u s e d i s p l a c e m e n t c a s - c a d e s and t h e r e f o r e extended damage zones, which might be amorphous, a s r e c e n t l y ob- s e r v e d 9 , w h i l e e l e c t r o n s a r e e x p e c t e d t o c a u s e r a t h e r s i m p l e d e f e c t s .

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261, 1981.