Formation of graphene atop a Si adlayer on the C-face of SiC

Abstract

The structure of the SiC( 1 000 ) surface, the C-face of the {0001} SiC surfaces, is studied as a function of temperature and of pressure in a gaseous environment of disilane (Si2H6). Various surface reconstructions are observed, both with and without the presence of an overlying graphene layer (which spontaneously forms at sufficiently high temperatures). Based on cross-sectional scanning transmission electron microscopy measurements, the interface structure that forms in the presence of the graphene is found to contain 1.4 -1.7 monolayers (ML) of Si, a somewhat counterintuitive result since, when the graphene forms, the system is actually under C-rich conditions. Using ab initio thermodynamics, it is demonstrated that there exists a class of Si-rich surfaces containing about 1.3 ML of Si that are stable on the surface (even under C-rich conditions) at temperatures above 400 K. The structures that thus form consist of Si adatoms atop a Si adlayer on the C-face of SiC, with or without the presence of overlying graphene.

The (3$\times$3)-SiC-($\bar{1}\bar{1}\bar{1}$) Reconstruction: Atomic Structure of the Graphene Precursor Surface from a Large-Scale First-Principles Structure Search

“…Vibrational entropy effects that modify the higher-temperature equilibria are considered in more detail in Ref. 28 . In the limit of sufficiently thick slabs, the surface energy γ of a two-dimensional periodic SiC slab with a C face and a Si face is given as…”

“…In a very recent publication 28 , Li et al (including some of us) presented a more detailed study of surface phases occurring prior to the onset of near-equilibrium growth of graphene on the C-face of SiC without and with temperature effects and presence of hydrogen. In Ref.…”

“…In Ref. 28 , a preliminary description of a new (3×3) surface reconstruction model was presented, which is known to occur along with graphene growth onset 14,[29][30][31][32][33][34][35][36][37] and the structure of which had previously eluded a definitive solution.…”

“…We note that further reconstructions with different periodicities were additionally addressed in Ref. 28…”

Order and disorder at the C-face of SiC: A hybrid surface reconstruction

“…This team has pursued its search and independently proposed the same ad-layer 2DL 1 as a possible candidate for the 3×3. 18 In order to understand why the 2DL 1 silicon over-layer does not reproduce the stm g condition it is necessary to analyze the interaction of this layer with the last carbon layer. Among the nine dangling bonds in the 3×3 cell, two are passivated by the silicon ad-atoms in top position (A and B sites), six are passivated by the three bridging Si connecting (O sites), the remaining dangling bond (C site) being not passivated.…”