Reconstruction and Thermal Stability of the Cubic SiC (001) Surfaces

Abstract

The (001) surfaces of cubic SiC were investigated with ab-initio molecular dynamics simulations. We show that C-terminated surfaces can have different c(2×2) and p(2×1) reconstructions, depending on preparation conditions and thermal treatment, and we suggest experimental probes to identify the various reconstructed geometries. Furthermore we show that Si-terminated surfaces exhibit a p(2×1) reconstruction at T = 0, whereas above room temperature they oscillate between a dimer row and an ideal geometry below 500 K, and sample several patterns including a c(4×2) above 500 K.Typeset using REVT E X 1

Multiconfigurational self-consistent field study of the silicon carbide (001) surface

“…The ϾCvCϽ dimer geometry on the C-SiC surface ͑001͒ is predicted to be symmetric by the CASSCF calculation, in qualitative agreement with the previous DFT calculations. 23,26,29 Symmetric dimers are also predicted on the diamond ͑001͒ surfaces by theoretical studies. 44,45 The NOON of the C-SiC ͑001͒ dimer orbital is slightly larger ͑i.e., smaller diradical character, stronger bond͒ than that on diamond ͑001͒.…”

“…This is different from the partially doublebonded 2ϫ1 dimer row on the diamond ͑001͒ surface. [43][44][45] Previous semiempirical, 19 LDA, 22 and GGA 20,24,26,29,32 calculations indicated that the bridging dimer is more stable than the staggered ϾCvCϽ dimer ͓Fig. 1͑c͔͒ on the C-SiC ͑001͒ 2ϫ2 surface, although the difference in energy between the two alternative reconstructions is small.…”

“…While the previous theoretical studies on SiC ͑001͒ surfaces were performed using empirical potentials, 15,16 semiempirical molecular orbital [17][18][19] calculations and DFT 14,[20][21][22][23][24][25][26][27][28][29][30][31][32] calculations, there have been virtually no ab initio calculations 33 performed on these systems. In particular, it may be important to employ multiconfigurational wave functions to describe the structures of SiC ͑001͒ surfaces by analogy with the dimer of the Si ͑001͒ surface, since the latter a͒ Electronic mail: tamura@cphys.s.kanazawa-u.ac.jp b͒ Electronic mail: mark@si.fi.ameslab.gov exhibits significant partial diradical character.…”

Dynamical-charge neutrality at a crystal surface

“…Our choice is the (001) Si-terminated surface of the zincblende semiconductor SiC, which has been the subject of recent theoretical work [9,10]. The actual structure is 2×1 reconstructed, but even the ideal (truncated bulk) one is insulating, and fits well our purpose of dealing with a test case as simple as possible: the sum rule for this case takes precisely the form of Eq.…”

Early Stages of Deposition of Nitrides on Cubic Silicon Carbide: A Theoretical Study

“…For both sets of calculations, the use of symmetric supercells is mandatory in order to avoid spurious charge transfer and electric fields [12].…”