THE NANOSCOPIC STRUCTURE OF ANNEALED GE20TE80 GLASS - QUASI-ATOMIC-SCALE IMAGING USING ATOMIC-FORCE MICROSCOPY

The nanoscopic structure of annealed Ge20Te80 glasses has been observed using atomic-force microscopy (AFM). The AFM images reveal to some extent the structure of amorphous semiconductors. AFM images as large as 20 x 20-50 x 50 nm(2) have shown many particles with diameters 2.5-3.5 nm-of the same order of magnitude as the interparticle distance. Since the peaks for each alignment lie at roughly the same height, it has been possible to image a couple of linear alignments 15-20 nm in length by AFM. The two-dimensional alignments generated a pseudo-surface (or infant surface) around 15 x 10 nm(2) in area. With the aid of our previous work on the quasi-atomic-scale images observed by scanning tunnelling microscopy and on the diffraction data from neutron scattering, the nanoscopic structure of annealed Ge20Te80 glasses can be interpreted in terms of short-range order (SRO), medium-range order (MRO) and supramedium-range order (SMRO) (the regions are similar or equal to 0.5 nm, similar or equal to 2.5-3.5 nm and similar or equal to 15-20 nm, respectively). The SMRO should be established by pseudo-ordered alignment or rings of the particles characterized by MRO of diameter 2.5-3.5 nm; the MRO should be established by pseudo-ordered arrangements among the structural units characterized by SRO.