Topographic and crystallographic characterization of a grazing-ion-bombarded GaAs(110) surface by time-of-flight ion-scattering spectrometry

Abstract

We studied the topography and the atomic structure of a clean GaAs(110) surface by time-of-flight ion-scattering spectrometry (TOF-ISS). In a first series of measurements the surface was cleaned by standard cycles of ion bombardment and annealing (500 eV Ar${}^{+}$, 500$\ifmmode^\circ\else\textdegree\fi{}$C). This method was very efficient to remove surface contaminants but not to smooth out the damage produced in TOF-ISS experiments. A cleaning method consisting of grazing bombardment with 20 keV Ar${}^{+}$ combined with annealing at 500$\ifmmode^\circ\else\textdegree\fi{}$C resulted in a clear improvement of the surface flatness. This was confirmed by measurements of electron energy distributions recorded under grazing proton bombardment and by a topographical analysis with an atomic force microscope. The crystallographic structure of the grazing ion bombarded surface was then studied by TOF-ISS. The quasisingle backscattered intensity measured for 5 keV Ne${}^{+}$ presented strong variations with the incident and azimuthal angles which are consistent with the generally accepted relaxed GaAs(110) surface. From the comparison of critical angles measured and focusing regions calculated with a code recently developed we have obtained an As-Ga first interlayer spacing $\ensuremath{\Delta}Z=(0.66\ifmmode\pm\else\textpm\fi{}0.08)$\AA{}, and the spacings between the first and second As layers $\ensuremath{\Delta}{Z}_{1,2}^{\mathrm{As}}=(2.25\ifmmode\pm\else\textpm\fi{}0.08)$ \AA{} and between the first and second Ga layers $\ensuremath{\Delta}{Z}_{1,2}^{\mathrm{Ga}}=(1.57\ifmmode\pm\else\textpm\fi{}0.1)$ \AA{}.