We present a scanning tunneling microscopy (STM) study of the initial stages of ZnSe deposition on the GaAs(001)-(2×4) surface. The deposition of elemental Se and of ZnSe on the bare GaAs surface induces considerable atomic disorder attributed to the Se–As exchange reaction. The deposition of elemental Zn weakens the 2× periodicity of the surface but induces no apparent changes in the STM images of the As dimers. Comparison of STM images of submonolayers of ZnSe on GaAs with and without a Zn pretreatment suggests that Zn reduces the interaction of Se with the GaAs surface.

The atomic geometry of the CuCKl 10)-(1 x 1) surface is determined by dynamical analysis of lowenergy electron-diffraction intensities. This surface undergoes a relaxation characterized by a -30° Cu-Cl surface bond rotation, a 0.15 A contraction of the top-to-second layer distance, and a 0.4 A horizontal displacement of CI relative to Cu. The relaxation is consistent with the "universal" structure deduced from the analysis of cleavage surfaces of tetrahedrally coordinated III-V and II-VI compounds, thereby revealing that this feature of the structure does not depend significantly on the ionicity of the compound.PACS numbers: 61.l4.Hg, 68.35.BsFor decades the study of the dependence of surface atomic geometries on parameters characteristic of the bulk chemical bonding [1,2] (e.g., crystal class, lattice parameters, bonding character) has been a major topic in surface science. Historically, the cleavage faces of tetrahedrally coordinated compound semiconductors have been a fertile ground for the proposition and testing of such structure-bonding relationships because of their reproducible surface composition and extensive structure studies [3-5]. In recent years, however, the validity of earlier experimentally established scaling rules [6] has been questioned by a series of model predictions of the surface structures of the cleavage faces of zinc-blendestructure compounds [7]. The case of CuCl(llO) emerged from these predictions as a crucial test case in which the scaling rules failed completely [7]. Our purpose in this paper is to report a structure analysis of CuClO 10) revealing that it is compatible with the experimentally established scaling rules and hence constitutes a critical piece of experimental evidence that atomic size and surface topology rather than bonding ionicity are the dominant determinants of the surface atomic geometries of the (110) cleavage surfaces of zinc-blende-structure compound semiconductors. Zinc-blende (110) surfaces experience significant (-1A) relaxation of surface atomic positions from their bulk positions. Because of the reproducible 1:1 stoichiometry of these surfaces, the questions of the dominant driving force of the relaxations and their correlation with bulk structural and energetic parameters may be posed precisely. The earliest quantitative relaxation model predicted a link between relaxation and ionicity based on the small-molecule chemistry of the threefold-coordinated surface species [8]. According to this model, the surface anion and cation of mostly covalent III-V compounds would assume pyramidal p-like and planar 5"p 2 -like bonding configurations, leading to the observed bond rotation, whereas their counterparts on the more ionic II-VI compounds would not. Yet, all geometries subsequently determined appeared to be largely independent of the ionicity of the compound, exhibiting an approximately constant bond rotation angle of 29° ±3° [4,5]. Moreover, atomic displacements were found to scale in such a way that all materials exhibit the same basic structure when dimensi...

Epitaxial layers of the ionic zinc blende compound CuCl are grown on the (110) surface of GaP. The growth is performed by congruent evaporation from a single CuCl source. Surface and interface properties of CuCl/GaP are studied with Auger electron spectroscopy, ultraviolet and x-ray photoemission spectroscopy, electron energy-loss spectroscopy, and low-energy electron diffraction. The interface formed at 100 °C is abrupt, but undergoes a massive chemical reaction which leads to the formation of a copper phosphide layer at high temperature (≥300 °C). The valence band discontinuity is 0.85 eV ±0.15 at the abrupt CuCl/GaP interface. The CuCl(110) surface is atomically ordered and exhibits a (1×1) unit cell. Its atomic geometry is determined by multiple scattering analysis of low-energy electron diffraction intensities. The surface is found to be relaxed in a way which is entirely compatible with the ‘‘universal’’ structure of cleavage surfaces of tetrahedrally coordinated III–V and II–VI compound semiconductors.