Surface roughening of Ge(001) during 200 eV Xe ion bombardment and Ge molecular beam epitaxy

Abstract

The kinetics of surface roughening of Ge(001) during 200 eV Xe ion bombardment and during Ge molecular beam epitaxy (MBE) are studied by real-time reflection high-energy electron diffraction. In both cases, initially smooth surfaces reach a steady state roughness which depends on temperature and incident ion or adatom flux. The data are analyzed in terms of a phenomenological model in which beam-induced roughening competes with beam-induced smoothening, and in which the defect creation rate and surface diffusivity are fitting parameters. For comparable fluxes, the temperature dependences for the net roughening induced by ions and adatoms are strikingly similar, implying a similarity in the surface diffusivities of vacancies and adatoms. For the case of ion-induced roughening, approximately one surface defect (in units of displaced surface atoms) is created per ion which is consistent with calculations assuming that a large fraction of atomic displacements recombine without producing surface defects at these ion energies.