Phase Formation Study In Alpha-Al2o3 Implanted With Niobium Ions

Niobium ion.s of 150 keV energy have been implanted at temperatures of 77 or 300 K in α-Al 2 O 3 with doses ranging from 5 × 10 15 to 3 × 10 17 ions/cm 2 and subsequently thermal annealed up to 1273 K in H 2 gas or in air. The structure of the implanted layer has been characterized by X-ray diffraction at glancing incidence and its physical properties have been investigated by means of optical absorption spectroscopy and electrical conductivity measurements. For implantation performed at 77 K, the sapphire reaches an amorphous state at a fluence of 5 × 10 15 ions/cm 2 whereas an implantation dose of 5 × 10 16 Nb/cm 2 is required at 300 K. For heavily implanted samples the amorphous layer has an electrical resistivity typical of poor metal. Annealing treatment performed in Hi gas leads to the formation of an Nb 2 O 5 oxide plus clusters of niobium, whereas a NbA10 4 compound is observed after annealing in air.