LATTICE DISORDER IN ALPHA-AL2O3 INDUCED BY NIOBIUM IMPLANTATION

The effects of 150 keV Nb ion implantation on α-Al2O3 single crystals have been investigated using Rutherford backscattering channeling technique and optical absorption measurements. Analysis of the implantation and damage profiles have been performed on samples implanted with doses ranging from 5 × 1014 to 1017 Nb+ cm-2. The experimental implantation and damage distributions have been compared with TRIM code calculations. For the lowest implantation doses (< 1015 ions cm-2) the damage distribution and the implantation profile are in good agreement with TRIM predictions assuming a displacement energy for oxygen and aluminium atoms of 75 eV and 16 eV respectively. For doses higher than 1015 ions cm-2 a concomittant inward shift and broadening of the defect profile is observed probably due to a defect migration which occurs during the ion implantation process. For doses higher than 5 × 1016 ions cm-2 the defect concentration increases leading to the formation of an amorphous layer. A comparison between RBS channeling analysis and optical absorption measurements has been made in order to make clear the nature of the ion implantation damages and to ascertain the amorphization mechanisms. © 1990.