Surfaces of GaAs and Ga1-xMnxAs nanolayers

Igor Bartoš

These crystalline - promising for the spintronics - materials are prepared as nanolayers by the low-temperature molecular epitaxy and their properties are affected by the sample surfaces. Surface sensitive methods provide information about the crystallography of their reconstructed surfaces and about their electronic and magnetic properties.

Atomic configurations of reconstructed GaAs(100)c(4x4) surfaces (phases alpha and beta) can be extracted from measured intensities of low-energy electron beams back diffracted from the surfaces by the dynamical theory interpretation of the I-V curves. Surfaces with homo- (As-As) and hetero- (Ga-As) dimers in the two phases can also be distinguished from core level electron energy shifts detected in photoelectron spectroscopy.

Magnetic properties of Mn-doped GaAs samples are determined by Mn incorporation into the GaAs lattice: ferromagnetism is connected with substitutional Mn atoms whereas it is suppressed by interstitial Mn atoms. Role of preparation procedures in the proper incorporation of Mn atoms is studied by the sample dichroism (circularly polarized radiation available e.g. from synchrotron sources Elettra Trieste, Max Lab Lund). Photoelectron diffraction from Mn core levels enables to determine local coordination of these atoms in the lattice.