Recoil - ion fractions in collisions of keV Ar+ and Kr+ ions with clean and adsorbate covered GaAs(110) surfaces

J.E. GAYONE; E.A. SÁNCHEZ; O. GRIZZI; L.I. VERGARA; M.C.G. PASSEGGI (JR.); R. VIDAL; J. FERRÓN

NUCLEAR INSTRUMENTS AND METHODS IN PHYSICS RESEARCH B - BEAM INTERACTIONS WITH MATERIALS AND ATOMS

Elsevier

Lugar: Amsterdam; Año: 2002 vol. 193 p. 440 - 448

0168-583X

Ion scattering and recoiling spectroscopy with time of flight analysis is used to study the ion fractions in Ga and As atoms recoiled in collisions of 5 keV Ar+ and Kr+ with clean GaAs(110) and with GaAs(110) covered with H, alkali metals (K and Cs), and fluorides (AlF3). For the case of the clean surface, the ion fraction in Ga direct recoils is positive,  large (~50%), and independent of the projectile type. The ion fraction in As direct recoils is also positive, low for Ar+ (<10%) and relatively large (25%) for Kr+ projectiles. The adsorption of H produces slight changes in both the As and Ga ion fractions, while the adsorption of alkalis produces strong changes that can be correlated to the adsorption kinematics and the preferential adsorption sites. At the beginning of the alkali adsorption the neutralization of Ga recoils increases fast with the coverage and follows approximately the variation of the work function. At coverages above half of the saturation value, where the work function has attained a stable value, the ion fraction in Ga remains low and stable while that in As changes, the positive ion fraction decreases and the negative ion fraction increases. The adsorption of AlF3 produces no change in the Ga and the As ion fractions, supporting a non-dissociative and weak reacting model for adsorption.