Amorphization Induced by Ball — Milling in Some Pure Elements: Si, Ge

Abstract

We report on the crystal to amorphous phase transition induced by ball — milling in pure Si and pure Ge powders. Based on X-ray diffraction patterns, scanning and transmission electron micrographs, EDX microanalyses, differential thermal analyses and differential scanning calorimetry, it seems that amorphization occurs during the continuous decrease of the particle grain size and the crystalline lattice parameter expansion which both lead to the destabilization of the diamond cubic structure. The analyses of the X-ray diffraction patterns reveal the coexistence of microcrystallites and of an amorphous phase. The transmission electron microscopy investigations reveal that some particles of about 100 to 200 nm exhibit an amorphous structure (bright field image and selected area diffraction patterns). Only some slight effect of the ball — milling onditions are noted on the critical values of the grain size and the lattice expansion of such a destabilization.