| Full text | |
| Author(s): |
Guilhon, I.
;
Teles, L. K.
;
Marques, M.
;
Pela, R. R.
;
Bechstedt, F.
Total Authors: 5
|
| Document type: | Journal article |
| Source: | PHYSICAL REVIEW B; v. 92, n. 7, p. 12-pg., 2015-08-24. |
| Abstract | |
The energetics and thermodynamic properties of two-dimensional binary graphene-like alloys made from graphene, silicene, or germanene are investigated by combining first-principles total energy calculations, and a statistical approach to account for disorder and composition effects. For the electronic properties the calculations are performed within the GGA-1/2 approach for an approximate quasiparticle bands. We derive lattice constants, first-neighbor distances, and buckling parameters as a function of composition x. The Si1-xGex system is the only stable random alloy at usual growth temperatures. For Ge1-xCx, we observe strong distortions of the lattice making the random configurations less favorable and leading to a pronounced tendency for phase separation. The situation for Si1-xCx alloys is completely different. An ordered structure with composition x = 0.5 is stable up to T approximate to 1000 K, while intermediate compositions are mainly realized by silicongraphene and graphene or silicene. The ordering and decomposition effects have a strong influence on the average fundamental energy gap versus composition. Whereas large gaps appear for Si1-xCx systems they almost vanish for Ge1-xSix and Ge1-xCx. Moreover, the dependence of the Si1-xCx energy gap on growth temperature is also obtained. The results can be very useful for chemical vapor deposition growth of these materials. (AU) | |