Analysis of the band structure of tetrahedral diamondlike crystals with valence bonds: Prediction of materials with superhigh hardness and negative electron affinity

Abstract

In the present paper, an analysis of the energy gap E gap , work function X, lattice constant L, and some other characteristics of the tetrahedral diamondlike crystals was performed in the framework of tight-binding bandstructure theory. Comparison with experimental data for diamondlike carbon films illustrates a good agreement with the obtained results, providing the possibility to estimate indicated parameters using the relation: E g ϩXϭ5.3 eVϪE v . The materials with extreme properties ͑hardness, exceeding that of natural diamond; high values of negative electron affinity, etc.͒ have been predicted.

Pressure dependence of the energy gaps in diamond-type semiconductors, and their III-V analogues such as InSb

“…(1) is more appropriate to describe a SMT close to the critical point, i.e. a vanishing band gap at a finite lattice parameter a ∼ a c , it is important to note that Litovchenko [6] has verified a correlation E g ∝ 1/a 2 , which agrees with experimental data for a a c , and is justified by the asymptotic, low-a power-law dependence of the energy matrix elements on the lattice parameter a within the tight-binding approximation [7]. That an SMT transition is related to a change in lattice parameter is also confirmed by the empirical correlation between the transition pressure in semiconducting chalcogenides and an appropriate average of the cation and anion radii [8].…”

Analysis of the Fundamental Characteristics of Diamond-Like Crystals and Low-Dimensional Structures

“…on the distance between the atoms, r AB = a A +a B , directly related to L (in particular, for tetrahedral lattice configurations: L = 2/ √ 3r AB , a is the valence radius). Such a dependence was obtained in the series of publications (by Shockley, Slater, Ioannopoulos, Harrison et al, see [1]). An important and unexpected point is that this dependence is nearly the same for all cubic semiconductor crystals of the fourth group in the periodical table of elements, namely for carbon in its diamond modification, silicon, germanium in cubic modification as well as the compounds of these crystals, such as SiC, SiGe and others rather rarely used, such as GeC, GeSn, SiSn.…”

“…Electronic properties of the FC-cubic crystals with dominating valence bonds were analysed in different approximations (LCAO, tight-binding pseudopotential up to ab-initio in Carparinello approach) and have been considered by many authors (Shockley, Slater, Harrison etc., see [1]). The important general conclusion that is possible to draw is that the first energy bands (conductance band edge E C , valence band energy E V for k = 0) dependence on the lattice length constant L is common for all crystalline materials of the fourth group of the periodical table of elements (β−C, Si, Ge, Sn, SiC, SiGe, IV A , IV B as well as for many III-V crystals with relatively small part of type of bonds).…”

Электронное строение монослойных сверхрешеток (GeC)-=SUB=-1-=/SUB=-(SiC)-=SUB=-1-=/SUB=-, (SnC)-=SUB=-1-=/SUB=-(SiC)-=SUB=-1-=/SUB=- и (SnC)-=SUB=-1-=/SUB=-(GeC)-=SUB=-1-=/SUB=-

“…Энергия обрезки плоских волн выбиралась равной 40 Ry, интегрирование по зоне Бриллюэна проводилось на сетках 6 × 6 × 6 (для кристаллов) и 6 × 6 × 4 (для СР). Путем оптимизации геометрии и минимизации полной энергии исследуемых кристаллов были вычислены сле-дующие значения постоянной решетки: 4.377 ¦ (SiC), 4.612 ¦ (GeC), 5.106 ¦ (SnC); которые адекватны дан-ным других авторов, например, [13][14][15][16][17][18] …”