Electrodeposition of Bi films on H covered n-GaAs(111)B substrates

Abstract

We have investigated how the presence of an adsorbed hydrogen layer affects the nucleation and properties of Bi layers grown by dc electrodeposition at different overpotentials on n-GaAs(111)B substrates with a carrier concentration of 1.3.10^17 cm^-3 in darkness and at 300 K. The kinetics of Bi(III) ions reduction is controlled by the overpotential but also negatively affected by the adsorbed hydrogen layer, as deduced from the deconvolution of the current density transients recorded during the nucleation of the films. The surface morphology and the structural properties of the Bi films are correlated with the nucleation process and therefore, influenced by both the overpotential and the adsorbed hydrogen layer. At low overpotentials, porous and rough Bi films with a low crystal quality are obtained due to the low rate of proton and Bi(III) ion reduction. As the overpotentials raises, the rate of these reactions increase leading to flatter and more compact Bi films with a higher crystal quality. The electrical properties of the Bi/n-GaAs interface depend on the interfacial states whose origin is again the combined effect of the adsorbed hydrogen layer and growth overpotential. (C) 2019 Elsevier Ltd. All rights reserved.