STM study of the C-inducedSi(100)−c(4×4)reconstruction

Abstract

We report a direct and reliable way to produce the Si͑100͒-c(4ϫ4) reconstruction by submonolayer deposition from a SiC source and subsequent annealing. Auger electron spectroscopy, low-energy electron diffraction, and scanning tunneling microscopy ͑STM͒ investigations reveal that a C amount equivalent to 0.07 monolayers ͑ML's͒ is sufficient to obtain full coverage of the c(4ϫ4)reconstruction. A deposition of 0.035 ML's C produces a c(4ϫ4)coverage of only 19%, indicating that C is not only present in the c(4ϫ4)areas, but also in the 2ϫ1 areas. There is not enough C to make it a regular part of the c(4ϫ4) reconstruction and we therefore conclude that the c(4ϫ4) reconstruction is strain induced. We find that a combination of the mixed ad-dimer and buckled ad-dimer models explains all main features observed in the STM images. Images of freshly prepared c(4ϫ4) surfaces exhibit a decoration of approximately 50% of the unit cells, which is attributed to perpendicular ad-dimers. Long exposures (Ͼ20 h) to the UHV background gas quench these features and the c(4ϫ4) reconstruction appears as if more homogeneous.

Step structure and surface morphology of hydrogen-terminated silicon: (001) to (114)

“…Naval Research Laboratory,Code 6177,4555 Overlook Avenue SW,Washington,DC,20375 8. PERFORMING ORGANIZATION REPORT NUMBER…”

“…Some surfaces will undertake extreme morphologies to assure a low-energy configuration. Roughening [2,3], faceting [4,5], growth mode modification [6,7], and surface reconstructions [8][9][10] are just a few of the properties that are directly tied to surface temperature and/or adsorbate coverage (i.e. chemical potential).…”

Modeling of the carbon-rich c(4×4) reconstruction on Si(100)

“…As we mentioned in Section 1, an alternative picture for the c(4 · 4) reconstruction is given by the experimental work of Jemander et al [10]. These authors proposed that with a deposition of only 0.07 ML of C they were able to get a homogeneous coverage of the whole surface with the c(4 · 4) reconstruction.…”

“…Regarding the last issue, there have been reports [2,10] suggesting that the reconstruction is formed even at very low C contents, below 0.1 monolayer (ML) coverage, corresponding to less than one C atom per c(4 · 4) unit cell. This means that C does not need to be a regular part of the reconstruction, but that it can induce the c(4 · 4) pattern through the strain field produced by its incorporation.…”

“…The structure of the carbon-induced c(4 · 4) reconstruction on the Si(1 0 0) surface has been the subject of intense investigations over the last years [1][2][3][4][5][6][7][8][9][10]. The change from the well-known c(2 · 4) or p(2 · 2) reconstructions of the pure Si surface to the c(4 · 4) pattern, with four dimers per unit cell, takes place after carbon (C) deposition at 600°C.…”