Formation of solid krypton bubbles in aluminium as investigated by a channelling method

Abstract

The behaviour of Kr atoms in aluminium has been investigated by an ion channelling method with a He⁺ beam on Al specimens implanted at room temperature at 50 keV to various doses from 1 × 10¹⁴ to 1 × 10¹⁶ Kr/cm². The Kr atoms are distributed over random (R), substitutional (S), tetrahedral (T) and octahedral (O) sites. From the implantation-dose dependence of the site occupancies, it is considered that, at the initial stage of implantation, Kr-vacancy (V) complexes such as KrV ₄ and KrV ₆ are formed and they act as nucleation centres for the subsequent growth to bubbles. KrV ₄ and KrV ₆ complexes are dissociated around 433 and 593 K, respectively. It is observed that post-implantation irradiation enhances the formation of solid krypton. On the basis of this result the mechanism for solidification of bubbles is discussed.

Key Words:

• Channelling
• Krypton bubbles
• Solid krypton
• Aluminium
• Irradiation
• Kr-vacancy complexes