Ion Implantation und Ion Irradiation

In general, for the application of ion implantation to the fabrication of (buried) nanostructures two physical principles can be used.

According to the left-hand side of figure, a far-from-equilibrium state is formed by ion implantation, which relaxes towards equilibrium during annealing. Although it was shown theoretically that self-organization of nanocrystals (NCs) occurs during relaxation towards equilibrium, it will become difficult to achieve a process control which is sufficient for technological application. It can be emphasized that the potential for tailoring of size and size distribution of NCs by a control of the process parameters of ion implantation and subsequent annealing is rather limited.

Recently, it has been demonstrated that a variation of temperature and ion flux during ion implantation can control the size distribution of NCs, at least to a certain extent. On the other hand, it was predicted recently that size and size distribution can be tailored efficiently by high-energy irradiation through a layer of NCs (right-hand side of the figure). Under the steady-state condition of an appropriate ion irradiation, an effective negative interface tension or capillary length appears in the Gibbs–Thomson relation for NCs embedded in a matrix. Therefore, the system of NCs evolves towards a maximum interface area, which is reached for a monodisperse size distribution (if nucleation of additional NCs is not allowed).

 
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