Surface States- and Field-Effects at GaAs(100) Electrodes in Sodium Dodecyl Sulfate Acid Solution

Abstract

Sodium dodecyl sulfate (SDS) effects at the electrified p-and n-GaAs(100)/H 2 SO 4 interfaces were investigated by EIS, XPS and AFM. XPS data revealed that under the open circuit conditions, SDS adsorption on GaAs(100) results in a protective overlayer which prevents the further oxidation in air of both types of semiconductor surfaces. The dopant nature is, however, decisive for the way of bonding the surfactant molecule to the surface. At the p-doped substrate, SDS adsorbs mainly at As sites by its hydrocarbon tail and by the anion head to the Ga sites at the n-doped one. Although the surfactant behaves as a dipole under the applied potential control, the dopant type plays a key role in the SDS interaction with GaAs(100) electrodes too. EIS data evidenced that SDS interaction with n-GaAs(100) electrode brings a pronounced decrease of the capacitive contribution of the surface states and a shift of the flatband potential to less negative values, unlike the p-doped one, where no significant change in its electronic properties was observed. These results were rationalized in terms of surface states-and field-effects operating at the electrified interfaces under discussion.

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

“…Taking into account the data obtained with the analysis of the current density transients we can conclude that the principal SSext that influences on the electrochemical properties of an n-GaAs electrode is the upper level of the AsGa antisite defect (0.75 eV + EV,s). This result is in agreement with the recent work of M. Enache et al [57] where they show that the principal group of electronic states at n-type GaAs electrodes is located at 0.7 eV below the bottom of the CB.…”

Surface states mediated charge transfer in redox behavior of hemin at GaAs(100) electrodes

“…Our previous investigations revealed an important group of donor-like surface states centred at about 0.4 eV above the semiconductor valence band edge, 15,17 at p-GaAs(100) and of another one of acceptor-like surface states located at about 0.7 eV below the conduction band edge at n-GaAs(100). 15,17,45 Quite similar to the deep surface states reported in literature, [46][47][48][49][50] they were associated with a missing Ga defect, As Gaantisite, considered responsible for the Fermi level pinning on p-GaAs(100), 47 and with an As decit, Ga As , regarded as the main electron trap in n-GaAs(100), 51 respectively. The difference in their energetic position of 0.3 eV is similar to the difference of about 0.3 V between the potential values at which occurs the cathodic reduction of hemin at the p-and n-GaAs(100) electrodes as seen in Fig.…”

“…The further examination of the hemin-covered GaAs electrodes by second harmonic generation, X-ray photoelectron spectroscopy and atomic force microscopy pointed to a possible change in the spin conguration of the iron ions preceding the charge transfer step originating in the mutual interactions between solvent, hemin and surface sites. 12 Since surface states and eld effects were found to depend signicantly at GaAs electrodes on both the surface orientation and the charge carrier type, [14][15][16][17] the comparison between the redox behaviour of hemin on Siand Zn-doped GaAs(100) in the same electrolyte should give a good hint about the role played by the charge carrier type in this charge transfer process. It is the aim of this paper to present the results of our electrochemical impedance spectroscopy (EIS) and X-ray photoelectron spectroscopy (XPS) investigations in this respect.…”

First-principles theory for Schottky barrier physics

“…The band gap of the reconstructed surface is 0.63 eV. 31 Such surface reconstruction creates surface states in the valence band and in the conduction band 32,33,34,35 which are partially filled (see Fig. 7a).…”