X-RAY INVESTIGATION OF ELECTRON-IRRADIATED QUARTZ

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X-RAY INVESTIGATION OF ELECTRON-IRRADIATED QUARTZ

D. Grasse, D. Müller, H. Peisl, C. Laermans

To cite this version:

D. Grasse, D. Müller, H. Peisl, C. Laermans. X-RAY INVESTIGATION OF ELECTRON- IRRADIATED QUARTZ. Journal de Physique Colloques, 1982, 43 (C9), pp.C9-119-C9-122.

�10.1051/jphyscol:1982923�. �jpa-00222452�

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CoZZoque C9, supple'ment au no12, Tome 43, de'cembre 1982 page C9-119

X-RAY INVESTIGATION OF ELECTRON-IRRADIATED BUARTZ D. ~rasse+, D. ~iiller+, H. ~eisl+ and C. Laermans ++

+Sektion Physik der Luhig-Maximilians U n i v e r s i t a t , 8000 Munchen 22, F. R. G.

++Lab. Vast Stof-en Hoge Dmkfysika, K.U. Leuven, CeZestijnenlaan 200 D, 3030 Leuven, Belgium

R6sum6.- L'6tude aux rayons de monocristaux de quartz irradigs aux electrons (dose 1,s x 102'e/cm2) sur lesguelr des mesures de conductivit6 thermique ont &t6 faites auparavant n'a pas mon- tr6, dans des limites d'erreur exp6rimentale1 de diffusion pro- venant des rBgions amorphes, ni de changement de paramstre de r6seau ou de diffusion prss des pics de BRAGG. Contrairement aux mesures pr6c6dentes sur les monocristaux de quartz irradi6s aux neutrons, les resultats concernant la conductivit6 thermique ne peuvent etre expliqu6s par des r6gions amorphes d6formant le r6seau.

Abstract.

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An X-ray study on 5lectron-irradiated quartz single crystals (dose 1.8 x 1020 e/cm ) on which thermal conductivity measurements had been made before showed within experimental error no scattering of amorphous regions, no lattice parameter change and no diffuse scattering intensity close to Bragg peaks. In con- trast to similar earlier measurements on neutron-irradiated quartz single crystals, the results of thermal conductivity cannot be explained by amorphous regions distorting the lattice.

Introduction.

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A new approach for a better understanding of the micro- scopic origin of the tunn l'n states (TLS) in amorphous solids has resulted from measurements'-t in n-irradiated crystalline quartz, which show the low temperature dynamical behaviour characteristic of glass. But n-irradiation creates defective (or amorphized) regions5 which show the amorphous scattering characteristic for glass. The crystalline matrix is heavily strained by the defective regions.

Electrons are expected to cause rather simple defects. From measurements of the thermal conductivity it was deduced6 that e-irradiation also creates TLS. To avoid influences of the sample state our measurements were made with the same sample as in Ref. 6.

Experimental results.

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The intensity distribution of scattered Cu K,, X-rays reflected from a bent quartz monochromator was measured point by point for various settings of crystal and detector angle. The pri- mary intensity from a stabilized kW rotating anode X-ray generator was monitored by a second counter9: Fig. 1 shows different diffracto- meter scans in the vicinity of the first strong diffuse halo in vitreous or glassy SiO2. It can be seen that within the experimental error no scattering of amorphous regions was detected.

We also compared the lattice parameter a, measured by the ~ o n d ~ method, of the e-irradiated sample with one of the same origin and found, that the lattice parameter change has to be smaller than 5 x 10-5.

Fig. 2 shows measurements of the diffuse scattering close to the (22z0)-

Article published online by EDP Sciences and available at http://dx.doi.org/10.1051/jphyscol:1982923

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C9-120 JOURNAL DE PHYSIQUE

reflection. During the measurements the crystals were kept near 12 K in order to minimize the thermal diffuse scattering. This measurement

.I50 .I 83

sin 0 [g-I]

X

Fig. 1 : Diffuse scattered intensity versus scattering vector. x glass irradiated with 4.9 x 1019 n/cm2,

+

quartz crystal y-irradiated oequartz crystal e-irradiated with 1.8 x 1020 e/cm2

also shows no defect induced scattering intensity.

2 2

Discussion.

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In Ref. 6 the ratio (noM ) e-irradiated/(n M ) vitreous silica = 7.3% was determined. For n-irradiation analogoug ratios can be explained by the volume fraction of the amorphous regions. In the case of the e-irradiation 7.3% of the crystal has to be amorphized, if the coupling constant M is the same in e-irradiated quartz and vitreous silica. Fig. I , however, shows that the volume fraction of amorphized regions has to be smaller than 3%.

If defects with the same strain as in n-irradiated quartz ( 3 ~ 1 0 ~ * n / c m ~ ) are created by e-irradiation, from Fig. 2 it can be deduced, that the defect concentration has to be 30 times smaller for the e-irradiated sample. But in this case the ratio of n M~ mentioned above are hard to explain. For this we conclude that in tRe e-irradiated sample no such large defective regions as in the n-irradiated sample are present.

To evaluate an upper limit of the strain per defect which is consistent with our measurements, we assume that the defect concentration of the e-irradiated sample is two times larger than in the n-irradiated sample as it may be indicated by the values n o ~ 2 o f Ref. 6. From the limit of the lattice parameter change with the above assumption for the defect

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scattered X-ray jn- tensity near (2290)- reflection in [I 1201

-

direction, o and a

quartz crystal irradiated with

1.8 x

loz0

e/cm2;

x natural quartz crystal

concentration the strain per defect has to be smaller than 0.43 0

(nmean atomic volume). This means, that the defect associated with TLS distorts the lattice only weakly.

A

new possibility or an explanation of TLS comes from the observation of diffuse streaks6, which are explained by chains of Si and 0 atoms, where the 0 atoms may have

different positions. W? observe these streaks also after light n-irradiation (3 x 1018 n/cm ) and therefore this disorder may be connected with TLS.

This work was supported by the Bundesministerium fur Forschung und Technologie.

1. C. Laermans, Phys. Rev. Lett. 42 (1979), 250

2. B. Golding, J.E. Graebner, W . ~ F ~ a e m m e r l e and C. Laermans, Bull.Am.

Phys. Soc. 24, (1979), 495; B. Golding and _{J . E .} Graebner in "Phonon scattering condensed matter", ed. _{H . J .} Maris (Plenum Press, 1980) p. 1 1 .

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Lett. 46, (1981), 261; D. Grasse, 0. Kocar, H. Peisl and S.C. Moss Rad. E R . (in press)

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6. C. Laermans, A.M. de Goer and M. Locatelli, Phys. Lett. 80A, (1980) 3 3 ; A.M. de Goer, M. Locatelli and C. Laermans, Journ. d e h y s .

(Paris, 4 2 , C 6-78, (1981)

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9. R. ComGs, M. Lambert anZTA. Guinier, "Interactions o f Radiation with Solids", ed. A. Bishay (Plenum Press N.Y., 1967) pp. 319-339