GaP((1)over-bar(1)over-bar(1)over-bar) reconstructed surface studied with STM and LEED

We have studied GaP((1) over bar(1) over bar(1) over bar) reconstructed clean surface with scanning tunneling microscopy (STM) and low-energy electron diffraction (LEED). We found that the surface consists of six equivalent mirror-symmetric domains and each domain has stripe structure. The stripe directions tilt from three ((1) over bar(1) over bar2) directions clockwise and counterclockwise at the same angle, resulting in six domains. The stripe period and the tilt angle are 1.30 nm and 6.8degrees, respectively. Magnified STM images revealed that all stripes in one domain have the same protrusion unit along the stripe direction, and that the origin of the protrusion unit is arranged by two vectors for the inter-stripe direction. The same unit-vector in the stripe direction and the two unit-vectors in the inter-stripe direction constitute two different surface-reconstruction units, namely units 1 and 2. We assigned the reconstruction matrices of units 1 and 2 in one domain to ((2 5) (3 -1)) and ((2 5) (4 1)), respectively. A trial structure model assuming the same elements located at the protrusions well explains observed LEED patterns. (C) 2002 Elsevier Science B.V. All rights reserved.