Metastable structures of liquid-quenched and vapour-quenched antimony films

Abstract

Antimony foils/films have been prepared by liquid-quenching and by vapour-quenching. (1) Simple cubic (a=3.16 A), (2) f c c (a=4.61 A), (3) tetragonal (a=3.01 A, c=4.96 A and c/a=1.64) structures, and (4) a new rhombohedral (aH=4.12 A, cH=10.26 A and cH/aH=2.49) metastable structure have been observed in splat-quenched foils. The metastable rhombohedral phase transforms to the equilibrium rhombohedral phase (aH=4.30 A, cH=11.27 A and cH/aH=2.62) on heating. The simple cubic, f c c and tetragonal phases are converted in to a hexagonal close-packed (a=3.33 A, c=5.23 A and c/a=1.57) structure on heating in the electron microscope. The simple cubic and h c p phases correspond to the known high-pressure phases of antimony. The h c p phase does not transform on further heating. Films prepared by vapour deposition on substrates held at room temperature show the same metastable f c c and rhombohedral phases as observed in splat-quenched foils, in addition to the equilibrium rhombohedral phase. On heating, these metastable phases transform in the same way as the splat-quenched specimens. The films deposited at liquid air temperature are amorphous; on electron-beam heating, these crystallize first to an unidentified complicated structure and then to the equilibrium structure.