FIGURE 1. Optical and electron micrographs of vitrified Ge.

a, b, The Ge sample through the gasket aperture (between the diamond anvils) before and after the melting pulse. c, 300 nm segment of the 2 m sample fragment of vitrified Ge quenched at 7.9(7.1) GPa, showing globules in matrix. Energy-dispersive X-ray analysis of both shows only Ge and Cu (from the grid) to be present. d, Amorphous diffraction pattern obtained from all areas except the area including the globule indicated by the arrowhead. e, Amorphous diffraction pattern for the globule area. Laue spots, indicating crystalline character, are obvious. The crystal–glass boundary (at the arrow tip) is seen in the high-resolution image of f. The crystal has grown within a globule. Energy-dispersive X-ray analysis of both shows only Ge and Cu (from the grid) present (see Supplementary Information). Other globules in c are fully amorphous. This is reminiscent of the preferential crystallization of the LDA in Al₂O₃–Y₂O₃ polyamorphic transitions²⁹, and also in the molecular triphenyl phosphite case³⁰. Annular dark-field imaging (see Supplementary Information) proves that the globules in c are darker because they are thicker, protruding from the matrix as seen at the right edge of c. In the annular dark field they appear bright.