Atomic structure determination of the Si-rich β-SiC(001)3×2surface by grazing-incidence x-ray diffraction: A stress-driven reconstruction

Abstract

The atomic structure of the Si-rich ␤-SiC͑001͒ 3ϫ2 surface reconstruction is solved by grazing-incidence x-ray diffraction with surface and subsurface structure determination. The reconstruction involves three Si atomic planes ( 1 3 ϩ 2 3 ϩ1 Si monolayers͒ in qualitative agreement with ab initio theoretical calculations. The first plane includes Si dimers that are asymmetric with a 0.1 Å height difference between Si atoms while the second plane includes Si dimers having alternating long ͑2.41 Å͒ and short ͑2.26 Å͒ lengths resulting in long-range influence with no buckling of the top surface dimers, in strong contrast to other group-IV semiconductors. Dimerization is also shown to take place in the third Si plane with a dimer having a bond length at 2.38 Å. In addition, a large Si interlayer spacing is found between the reconstructed planes at 1.56 Å, significantly larger than that for bulk SiC ͑1.09 Å͒ and Si ͑1.35 Å͒ interlayer distances, indicating a very open surface. The results suggest that stress is at the origin of this complex surface organization.

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“…The structure includes three Si atomic layers at 1/3, 2/3 and 1 ML, respectively, on top of the first C atomic plane7891011 as illustrated in Fig. 1.…”

“…Indeed, at the end of the nineteenth century, Henri Moissan found SiC on a meteorite in the Diablo Canyon, Arizona 6 . The cubic 3C-SiC(001) surface is of special interest with its atomic structure and many of its properties driven by surface strain/stress relief 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 . This leads to a large number of surprising and interesting surface arrangements with more than ten different well-characterized surface reconstructions (such as 3 × 2, 8 × 2, 5 × 2, 7 × 2, …, (2 n +1) × 2; c(4 × 2), c(2 × 2)), ranging from Si-rich to C-rich systems including notably in the latter case, graphene 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 .…”

“…The cubic 3C-SiC(001) surface is of special interest with its atomic structure and many of its properties driven by surface strain/stress relief 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 . This leads to a large number of surprising and interesting surface arrangements with more than ten different well-characterized surface reconstructions (such as 3 × 2, 8 × 2, 5 × 2, 7 × 2, …, (2 n +1) × 2; c(4 × 2), c(2 × 2)), ranging from Si-rich to C-rich systems including notably in the latter case, graphene 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 . The atomic structures of these reconstructions are now well understood and established on the ground of advanced experimental techniques such as scanning tunneling microscopy (STM), synchrotron-radiation-based photoemission spectroscopy/diffraction (SR-PES, SR-PED), grazing incidence X-ray diffraction, low-energy electron diffraction, near-edge absorption fine structure and state-of-the-art ab-initio calculations 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 .…”

“…The atomic structure of the Si-rich 3C-SiC(001)-3 × 2 surface reconstruction is now very well understood and established on the basis of atom-resolved real-space STM 8 , synchrotron radiation-based grazing incidence X-ray diffraction 9 and PED 10 experiments, and ab-initio calculations 11 . The structure includes three Si atomic layers at 1/3, 2/3 and 1 ML, respectively, on top of the first C atomic plane 7 8 9 10 11 as illustrated in Fig. 1 .…”

“…1 . The first plane (1/3ML) includes dimer rows having asymmetric Si–Si dimers all tilted along the same direction, the second plane (2/3 ML) also includes dimer rows having alternating lengths and the third plane also has dimer rows 7 8 9 10 . This complex structure tends to reduce the surface strain.…”