Surface morphology and structural changes in insulators induced by high-current 60 keV Cu− implantation

Abstract

Surface morphology and structural changes of amorphous (a-), crystalline (c-) SiO2 and MgAl2O4 spinel, implanted with high-current Cu− of 60 keV, were studied using atomic force microscopy. Kinetic variation of the surface morphology was evaluated by changing dose rate from 1 to 100 μA/cm2. In the cases of a-SiO2 and c-SiO2, the surface morphology significantly varied with dose rate: dome-type textures in the lower dose-rate region caused radiation-induced roughening, while net-type ones in the higher region occurred with radiation-induced smoothing. Step-height measurements showed radiation-induced expansion and compaction for c-SiO2 and a-SiO2, respectively. Radiation-induced amorphization is responsible for the expansion processes of c-SiO2. Contrarily, no amorphization was observed in the spinel up to dose rates of about 100 μA/cm2, although radiation-induced swelling, due to defect accumulation, was discernible by the step-height measurement. The surface morphology and the roughness of the spinel were not very dependent on dose rate. The results of c-SiO2 and a-SiO2 indicate that both of them are subjected to enhanced changes in surface morphology and microstructures and that high-current implantation causes highly dynamic states in the near-surface region. On the other hand, the results for the spinel show pronounced stability and that the spinel may be used as an effective substrate for optical modification, even for high-current ion implantation.