Microstructural change of Al on H implantation

Abstract
Modifications to the subsurface layer of Al on 25 keV H2 + ion implantation to fluences of 4 × 1017 to 2 × 1018 H+/cm2 at room temperature were investigated by transmission electron microscopy (TEM) and elastic recoil detection (ERD) with 1.5 MeV He+. Numerous bubbles ranging in diameter from 50 to 1000 Å were observed with a sharp peak at 120 Å irrespective of the ion fluence. Stereomicroscopic observations revealed the depth distribution of the bubbles. At fluences greater than 6 × 1017 H+/cm2, a lateral layer of lower density compared with matrix was observed and named “Swiss cheese structure” since its estimated structure is similar to Emmental cheese containing many holes. This Swiss cheese structure causes the formation of new layers on a free surface, and plays a precursor role for blistering. Hydrogen depth profiling with ERD was performed on every specimen revealing the collapse of the implanted hydrogen profile due to the formation of the Swiss cheese structure.