Formation of GdAl2 Laves Phase in Gadolinium Zinc Oxide Epitaxy Film

The study involved the growth of zinc oxide (ZnO) by molecular beam epitaxy (MBE) film on a c-plane sapphire (Al₂O₃) substrate, followed by ion implantation of gadolinium (Gd) at a concentration of 4 × 10¹⁵ ion/cm² to a depth of 20 nm to produce GdZnO. Subsequently, the film was subjected to neutron irradiation using a ²⁴¹Am-Be flux that was moderated to 7 × 10⁴ n/s cm² by a 4.5-cm-thick wax. The neutron irradiation was conducted continuously for 7 days. The thermal energy generated from the neutron irradiation with Gd was sufficient to create a compound between the Gd and Al taken from the substrate, resulting in the formation of a GdAl2 crystal. This is due to the nuclear reaction between the thermal neutrons and Gd, which provided the energy needed to initiate the reaction. In addition, the reaction between Gd and Al resulted in the displacement of the indium (In), used as a dopant for ZnO fabricated by MBE, from the Gd site to the Al site, causing the Al exciton line to become the dominant near-band-edge emission.