Structures of molten Tl- and Bi-chalcogen systems

Topological insulator thin films starting from the amorphous phase-Bi2Se3 as example

“…The structure results are comparable to known similar amorphous semiconductor systems 35 , but specially to the structure of the liquid phase of Bi 2 Se 3 investigated by Usuki 36 . Our results show similar features as the liquid phase, e.g.…”

“…the position of the first and second peak in the S(K) and g(r) are almost at the same values. The first peak at r 1 ≈ 0.29 nm in g(r) corresponds to the same value in the liquid phase and is close to the corresponding first nearest neighbor distance in the crystalline phase of Bi 2 Se 3 37 ; the peak r 2 ≈ 4.18 nm was identified in the liquid phase as consequence of the building of a short-range order related to the crystalline phase 36 . After integration, the first peak in g(r) allows us to calculate the coordination number N c ≈ 3.2.…”

“…After integration, the first peak in g(r) allows us to calculate the coordination number N c ≈ 3.2. This value is less than that of the liquid state (N c,Liquid ≈ 4.12) 36 and is due to the amorphous phase, which builds more defined first neighbors in comparison to the liquid phase. From the slope of the reduced atomic distribution G(r) = 4πrn 0 [g(r) − 1] at small values of r (dashed line in Fig.…”

A determination of the partial structure factors of liquid TlSe using combined x-ray and neutron diffraction

“…The peaks that we find at 4 Å for both the Tl-Tl and Se-Se correlations are broadly similar to those reported for liquid Tl 2 Se 3 . Integration of the first peak in Se-Se yields an Se-Se coordination of 0.5 ± 0.1 which is close to the values of 0.38 and 0.63 reported by Usuki et al (1993) and Kameda et al (1990) respectively. The coordination number for the main peaks (calculated to the first minimum in g ij (r)) are Tl-Tl: 9 ± 1, Se-Se: 10 ± 1 and Tl-Se: 6.0 ± 0.5.…”

“…Most notable is the sharp dip in S TlSe (Q) at ∼1.5 Å−1 which is characteristic of chemical ordering in the liquid. Lague et al (1996) and Usuki et al (1993) have previously reported measurements of the total structure factor of liquid Tl 1−x Se x at various compositions. Each of theses authors observes a peak in the total radial distribution function at 2.35 Å which they attribute to the existence of Se polyanions at selenium-rich compositions.…”