Direct evidence by positron annihilation spectroscopy of defect distributions deeper thanRpin Ar+implanted silica glass

Mazzoldi, P.; Mattei, Giovanni; Ravelli, L.; Egger, Werner; Mariazzi, S.; Brusa, R. S.

doi:10.1088/0022-3727/42/11/115418

Cited by 12 publications

(10 citation statements)

References 21 publications

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“…So far the slow positron beam technique was applied to detection of defect range in implanted samples [11,12]. Mazzoldi et al studied silica glass implanted by Ar + ions of energy 30 keV using this technique [11].…”

Section: Introductionmentioning

confidence: 99%

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Defect Range and Evolution in Swift Xe-Ion Irradiated Pure Silver Studied by Positron Annihilation Technique

2017

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Variable energy positron beam and positron lifetime spectroscopy were used to study pure silver samples exposed to irradiation with swift Xe 26+ ions of energy 167 MeV with different dose: of 10 13 , 5×10 13 and 10 14 ions/cm 2 . The positron lifetime spectroscopy revealed the presence of dislocations or vacancies associated with dislocations. They are distributed at the depth of about 6 µm, and this correlates with the ion implantation range, i.e. 9 µm. However, some defects are observed also to a depth of about 18 µm. At the depth less than 1 µm from the entrance surface strong dependence of positron diffusion length on the dose is observed. It indicates the presence of interstitial atoms and/or dislocation loops as a result of Xe 26+ ions implantation.

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Section: Introductionmentioning

confidence: 99%

“…Mazzoldi et al studied silica glass implanted by Ar + ions of energy 30 keV using this technique [11]. They found defect distribution extending more than twice deeper than ion range.…”

Section: Introductionmentioning

confidence: 99%

Defect Range and Evolution in Swift Xe-Ion Irradiated Pure Silver Studied by Positron Annihilation Technique

2017

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“…In insulators with open volumes, i.e., a region with low electron density, e þ can also form positronium (Ps), an e þ -e − bound state. This process is very effective in v-SiO 2 where up to 80% of the implanted e þ forms positronium [20]. Ps exists in two spin states: the singlet state parapositronium (pPs, lifetime in vacuum τ p ¼ 125 ps) and the long living triplet state orthopositronium (oPs, lifetime in vacuum τ o ¼ 142 ns).…”

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confidence: 99%

Structural Evolution and Medium Range Order in Permanently Densified VitreousSiO2

et al. 2014

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Positron annihilation lifetime spectroscopy is employed to measure the size of the interstitial void spaces characterizing the structure of a set of permanently densified SiO 2 glasses. The average volume of the voids is markedly affected by the densification process and linearly shrinks by almost an order of magnitude after a relative density variation of 22%. In addition, x-ray diffraction shows that this change of density does not modify appreciably the short range order, which remains organized in SiO 4 tetrahedra. These results strongly suggest a porous medium description for v-SiO 2 glasses where the compressibility and the medium range order are dominated by the density variation of the voids volume up to densities close to that of α-quartz. Despite the absence of translational periodicity, the glassy structure is characterized by the presence of some degree of order on the short (SRO) and medium ranges (MRO) [1]. SRO is associated with well-defined first neighbors arrangements, which can be characterized in terms of bond lengths and bond angle distributions. The basic structural units composing the network of covalent glasses are coordination polyhedra packed in a nonrandom way to form a second level of organization, which typically extends over a length of a few interatomic distances [2,3]. The presence of MRO is revealed by the appearance of a first sharp diffraction peak (FSDP) in the static structure factor SðQÞ. The FSDP has been observed in a wide range of glasses, supercooled liquids, and even in melts at high temperature, displaying a universal dependence on temperature and pressure [4]. This suggests a common structural origin, associated to the atomic arrangement at the nanometer scale. Several interpretation schemes have been proposed to explain this feature. The layered structure of many glass-forming chalcogenide glasses has suggested the identification of the FSDP with a Bragg-like peak originated by pseudocrystalline arrangements [5]. On the other hand, the FSDP has been connected to the occurrence of characteristic low density regions [6,7]. These void structures are surrounded by chemically ordered clusters leading to correlation distances typical of the MRO [4]. Thus, the FSDP arises from a prepeak in the concentration-concentration structure factor in the Bhatia-Thornton formalism [8].The importance of the nanoscale structure in the glass transition phenomenology has been pointed out in recent numerical works highlighting some connection between heterogeneous dynamics [9] and the structural order [10,11]. The nanometer length scale is also relevant in the glassy state below the glass transition temperature, where it marks the transition from a macroscopic elastic regime to a microscopic one where the dynamics of the glass and that of the corresponding density polycrystal become very similar [12]. However, the knowledge of the real-space arrangement at the MRO scale is still elusive and practically accessible only in computer simulations. In fact, Fourier transform of the SðQÞ only prod...

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“…To understand the origin of the observed Ps increase, PALS measurements were carried out on the capped sample. In Fig.2 the three achieved lifetimes are reported as a function of E. Beyond the TiO 2 capping layer, E > 3 keV, the lifetimes are constant: τ 1 , due to an average of p-Ps self-annihilation and e + free annihilations in Si, results ≅ 200 ps [24], τ 2 , coming from the annihilation of e + trapped in the bulk silica layer at the nanochannels surface, is ≅ 420 ps [25] and τ 3 , due to o-Ps pick-off annihilation, is ≅ 48 ns. At E < 3 keV τ 3 is due to Ps annihilating in open volume in the TiO 2 capping layer while τ 1 , that reaches ≅ 250 ps, is compatible with e + lifetime in amorphous TiO 2 [26].…”

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confidence: 99%

Study of Positronium formation in nano-channelled silicon as a function of sample temperature

Mariazzi

DiNoto

Ravelli

et al. 2013

J. Phys.: Conf. Ser.

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Abstract. Oxidized nanochannel in silicon have been demonstrated to be suitable for positronium (Ps) formation and cooling also at low sample temperature. To investigate the Ps yield and to clarify the Ps formation mechanism we studied, by Positron Annihilation Spectroscopy (PAS), nanochanneled Si p-type samples in the 150-430 K temperature range. Ps yield was found to be constant in the 150-300 K temperature range, then it increases up to ~50% of its value from 350-400 K. This effect is associated to a decrease of the fraction of positrons annihilating in Si and in the SiO 2 layer on the nanochannels surface. This finding is compatible with the thermal decrease of the positive charge distribution at the Si/SiO 2 interface limiting e + reaching the SiO 2 layer and to a charge rearrangement at the SiO 2 surfaces.

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Direct evidence by positron annihilation spectroscopy of defect distributions deeper thanR_pin Ar⁺implanted silica glass

Cited by 12 publications

References 21 publications

Defect Range and Evolution in Swift Xe-Ion Irradiated Pure Silver Studied by Positron Annihilation Technique

Defect Range and Evolution in Swift Xe-Ion Irradiated Pure Silver Studied by Positron Annihilation Technique

Structural Evolution and Medium Range Order in Permanently Densified VitreousSiO2

Study of Positronium formation in nano-channelled silicon as a function of sample temperature

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