ABSTRACT
This chapter considers the formation and thermal stabilization of helium bubbles in amorphous layers produced in thin crystalline silicon (Si)films by low energy helium ion irradiation. The implantation of a helium ion beam in the required high doses into the semiconductor crystal causes inevitable radiation damage within the crystal. The repulsion force acting on the interstitial helium from single vacancies is sufficient to overcome the barrier for diffusion activation. This mechanism of diffusion activation is likely to be impossible in amorphous Si; therefore, a much lower mobility of helium dissolved in a-Si should be expected. During helium implantation into thin Si crystal containing an amorphous layer, nanobubbles are formed solely in this layer, because the mobility of helium atoms in amorphous Si is considerably lower than in the crystal under irradiation. Helium nanobubbles are aligned with the direction of ion motion throughout the radiation-induced amorphous layer.
