In-plane structure of an arsenic-adsorbed Si(001) surface probed with grazing-angle x-ray standing waves

The grazing-angle x-ray standing-wave technique has been employed for in-pl ane structure determination of an arsenic-deposited Si(001) surface with 1X 2 and 2X1 domains. Experimental data were collected using the (220), ((2) o ver bar 20), and (040) Bragg planes nearly perpendicular to the surface und er UHV conditions. Three arsenic-emission profiles were fit by calculations based on the x-ray dynamical theory for perfect crystals. The data analysi s allows us to limit the possible ranges of an As-As dimer bond length L, a n in-plane root root[u(parallel to)(2)], and the two domain fractions, M-1 and M-2. The ranges of the structural parameters, such as L and root[u(para llel to)(2)], are consistent with other works. In particular, L and a two-d omain area ratio M-2/M-1 are restricted within the narrow ranges from 2.57 to 2.52 Angstrom, and from 1.35 to 1.29, respectively. Assuming domains are perfectly ordered, it is found that L=2.52+/-0.05 Angstrom, root[u(paralle l to)(2)]=0.22 +/-0.07 Angstrom, M-1=0.44+/-0.07, and M-2=0.56+/-0.07. [S01 63-1829(99)03747-9].