Low flux and low energy helium ion implantation into tungsten using a dedicated plasma source

NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION B-BEAM INTERACTIONS WITH MATERIALS AND ATOMS

卷:383

Article

Pentecoste, Lucile¹  Thomann, Anne-Lise¹  Melhem, Amer¹  Caillard, Amael¹  Cuynet, Stephane¹  Lecas, Thomas¹  Brault, Pascal¹  Desgardin, Pierre²  Barthe, Marie-France² 

[1] Univ Orleans, CNRS, GREMI, 14 Rue Issoudun,BP 6744, F-45067 Orleans 2, France

[2] CNRS, CEMHTI UPR3079, 1D Ave Rech Sci, F-45071 Orleans 2, France

关键词: Ion implantation;    Ion energy distribution function;    Capacitively coupled discharge;    Helium implantation in tungsten;    Vacancy defect formation;   

DOI  :  10.1016/j.nimb.2016.06.011

来源: Elsevier

【 摘 要 】

The aim of this work is to investigate the first stages of defect formation in tungsten (W) due to the accumulation of helium (He) atoms inside the crystal lattice. To reach the required implantation conditions, i.e. low He ion fluxes (10(11)-10(14) ions.cm(2).s(-1)) and kinetic energies below the W atom displacement threshold (about 500 eV for He+), an ICP source has been designed and connected to a diffusion chamber. Implantation conditions have been characterized by means of complementary diagnostics modified for measurements in this very low density helium plasma. It was shown that lowest ion fluxes could only be reached for the discharge working in capacitive mode either in alpha or gamma regime. Special attention was paid to control the energy gained by the ions by acceleration through the sheath at the direct current biased substrate. At very low helium pressure, in alpha regime, a broad ion energy distribution function was evidenced, whereas a peak centered on the potential difference between the plasma and the biased substrate was found at higher pressures in the gamma mode. Polycrystalline tungsten samples were exposed to the helium plasma in both regimes of the discharge and characterized by positron annihilation spectroscopy in order to detect the formed vacancy defects. It was found that W vacancies are able to be formed just by helium accumulation and that the same final implanted state is reached, whatever the operating mode of the capacitive discharge. (C) 2016 Elsevier B.V. All rights reserved.

【 授权许可】

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