Swelling of SiO 2 Quartz Induced by Energetic Heavy Ions
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C. TRAUTMANN 1 , J.M. COSTANTINI 2 , A. MEFTAH 3 , K. 5 4 J. P. STOQUERT , AND M. TOULEMONDE
SCHWARTZ 1
1 Gesellschaft fuir Schwerionenforschung, Planckstr. 1, 64291 Darmstadt, Germany, [email protected] 2 DPTA/PMC, BP 12, 91680 Bruy6res-Le-Chdtel, France 3 ENSET, BP 26 Merj-eddib, 21000 Skikda, Algeria 4 Laboratoire PHASE, 67037 Strasbourg - cedex 2, France 5 CIRIL, Laboratoire commun CEA/CNRS, BP 5133, 14070 Caen-cedex 5, France ABSTRACT A pronounced swelling effect occurs when irradiating SiO 2 quartz with heavy ions (F, S, Cu, Kr, Xe, Ta, and Pb) in the electronic energy loss regime. Using a profilometer, the out-of-plane swelling was measured by scanning over the border line between an irradiated and a virgin area of the sample surface. The step height varied between 20 and 300 nm depending on the fluence, the electronic energy loss and the total range of the ions. From complementary Rutherford backscattering experiments under channelling condition (RBS-C), the damage fraction and corresponding track radii were extracted. Normalising the step height per incoming ion and by the projected range, a critical energy loss of 1.8 ± 0.5 keV/nm was found which is in good agreement with the threshold observed by RBS-C. Swelling can be explained by the amorphisation induced along the ion trajectories. The experimental results in quartz are compared to swelling data obtained under similar irradiation conditions in LiNbO 3. INTRODUCTION Radiation induced volume expansion is a general effect which has been discovered in various solids in the late fifties. The swelling under irradiation can result from point defects, but also from defect aggregates or from phase transitions. In the case of point defects, the swelling mechanism is well understood [1,2], while for more complex defects, i.e. under irradiation at higher doses, it is described only phenomenologically. In this regime, the relative volume changes are larger and, depending on the material, can reach several percent (e.g. 15% for quartz) [3]. Swelling occurs in a wide range of irradiation conditions (e.g. temperature, dose, and dose rate) and under various particle beams such as electrons, neutrons or ions [4-8]. More recently, swelling has been observed when irradiating A12 0 3 [9] and LiNbO 3 [10-12] with energetic heavy ions. The macroscopic volume increase of the bulk material was clearly attributed to the damage produced by electronic excitations. The goal of our study was to extend the swelling tests to SiO 2 crystals. It should be mentioned that in quartz, the damage under heavy ion irradiation has been studied by various techniques [7,13-15]. Evidence was given that along the ion trajectory a cylindrical zone of amorphous silica is formed having a diameter of a few nanometers. The experimental data are
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Mat. Res. Soc. Symp. Proc. Vol. 504 0 1998 Materials Research Society
in good agreement with the thermal spike model which describes the track as a cylindrical zone resulting from rapid quenching of a liquefied phase along the ion path [ 15]. In orde
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