Characterization of Cd1-yZnyTe(111) and Hg1-xCdxTe(111) real surfaces by x-ray photoelectron diffraction.

Abstract

The surfaces of ${\mathrm{Cd}}_{1\mathrm{\ensuremath{-}}\mathit{y}}$${\mathrm{Zn}}_{\mathit{y}}$Te(111) substrates and of lattice-matched ${\mathrm{Hg}}_{1\mathrm{\ensuremath{-}}\mathit{x}}$${\mathrm{Cd}}_{\mathit{x}}$Te epilayers have been investigated with use of x-ray photoelectron diffraction (XPD) to assess their crystalline properties, in particular termination, reconstruction, and relaxation, as well as structural imperfections induced by various etch treatments. In this context, we also explore the general analytical potential of XPD for the characterization of the surface structures of compounds. The azimuthal- and polar-angle-resolved photoemission recorded as a complete hemispherical pattern for the core levels of Cd 3${\mathit{d}}_{5/2}$, Te 3${\mathit{d}}_{5/2}$, and Hg 4${\mathit{f}}_{7/2}$ photoelectrons clearly revealed the phenomenon of photoelectron diffraction for the investigated surfaces. Modeling results indicate that the structure observed in the diffraction patterns can be interpreted simply in terms of zeroth-order interference or forward-direction focusing. Thus XPD is a powerful technique for imaging atoms in real space, and provides a complete description of the symmetry of the three-dimensional crystal lattice within the volume analyzed. The terminations of the examined (111)A and (111)B surfaces are easily differentiated and are found surprisingly to be almost perfect. We find no evidence for any reconstruction or relaxation of the (111) surfaces of ${\mathrm{Cd}}_{1\mathrm{\ensuremath{-}}\mathit{y}}$${\mathrm{Zn}}_{\mathit{y}}$Te and ${\mathrm{Hg}}_{1\mathrm{\ensuremath{-}}\mathit{x}}$${\mathrm{Cd}}_{\mathit{x}}$Te.