On Boron Diffusion in MgF2

• Main Authors: Vacik, J, Hnatowicz, V, Cervena, J, Posta, S, Koster, U, Pasold, G
• Format: Conference Proceeding
• Language: English
• ISSN: 0094-243X
• DOI: 10.1063/1.3120169

The MgF2 monocrystals were irradiated at room temperature with 390 keV B+ ions up to the fluence of 1016 cm-2. The irradiated samples were (isochronally and isothermally) annealed in high vacuum at the temperatures 200 deg C, 300 deg C, 400 deg C, 500 deg C, 600 deg C and 700 deg C for the times ranging from 2-100 hours. After each annealing step, the boron depth distribution was determined using the neutron depth profiling technique. As implanted, the depth distributions of boron exhibited standard Gaussian-like forms, but the evaluated profile parameters, RP = 960 nm and D RP = 140 nm, were higher than those calculated using the SRIM code (RP = 870 nm and DRP = 115 nm). Annealing at temperatures up to 400 deg C did not change the depth profiles. Annealing at 600 deg C, however, led to a one-way gradual transfer of the boron atoms from the site of implantation towards the sample surface, and in this way a bimodal profile was created. The amount of boron atoms, transferred to the sample surface, was an increasing function of the annealing time. After annealing at 700 deg C for 64 hours the bimodal profile collapsed into a single broad distribution, extending from the sample surface up to the implantation depth. The observed phenomena clearly points out the stability of the as-implanted boron depth profiles at lower annealing temperatures. Thermal annealing above 600 deg C, however, liberates boron atoms, which then predominantly migrate from the implantation site towards the sample surface, where they are captured on some unspecified surface defects.