Structure and existence of the first sharp diffraction peak in amorphous germanium prepared in UHV and measured in-situ

Abstract

The structure of “glassy” germanium films prepared by slow sublimation of germanium on heated substrates in ultra-high vacuum was investigated using in-situ high-energy transmission electron elastic scattering up to the scattering vector s = 4π/λ · sin θ ∼- 10 A ̊ −1 . It is shown that on the basis of the presently available experimental evidence, there exists a number of important physical constraints as to the structure of amorphous germanium. Furthermore, a diffraction pre-peak at the scattering vector s ⋍ 1.2 A ̊ −1 has been observed, the first such observation in tetrahedrally bonded elemental amorphous semiconductor. This result is discussed in the light of similar observations in other disordered systems. The significance of short- and medium-range real space correlations in disordered systems is pointed out.