Electrodeposition of Bi Thin Films on n-GaAs(111)B. I. Correlation between the Overpotential and the Nucleation Process

Abstract

Bismuth thin films constitute a promising nanostructure for the fabrication of spin-based devices. To achieve this goal, it is necessary to obtain high-quality Bi layers with controlled and reproducible properties. Therefore, studies focused on the understanding of the nucleation process and the correlation between the growth conditions and the film properties are of great interest. In this work, we have studied the electrodeposition of Bi thin films onto GaAs(111)B substrates at different overpotentials. In Part I, we have analyzed the nucleation of the films by means of potentiostatic curves. The current density transients have been deconvoluted into individual processes taking into account the energy band diagram of the semiconductor-electrolyte interface. The deconvolution of the current density transients indicates that Bi electrodeposition follows a 3D nucleation controlled by diffusion, accompanied by concurrent processes such as both proton adsorption and reduction. The competition of these processes is controlled by the energy distribution of the surface states at the semiconductor-electrolyte interface and determines the nucleation process. The correlation between the properties of the Bi films and the Bi/GaAs interface with the nucleation process, i.e., with overpotential, is discussed in detail in Part II of this work.

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

“…In the first scan we can observe a cathodic peak with an onset potential (defined as the intersection of the rising current of the cathodic peak with respect to its baseline) around -200 mV, whereas the second scan presents a reduction peak with a different shape and a more positive onset potential (≈ -100 mV). Taking into account our previous work, these two peaks consist of the superposition of those assigned to Bi(III) ion and H + reduction on the n-GaAs surface [13,10,9]. Despite the reduction peaks, no anodic peak is observed in the CV, i.e., the metallic Bi cannot be oxidized into Bi(III) ions during the anodic stage (inset Figure 1).…”

“…For cathodic reactions, where the current density is negative, the absolute value of j(t) should be used. We have elaborated a theoretical nucleation model based on several processes that occur in the SEI when it is biased, and that accurately describes the experimental nucleation curves for the electrodeposition of Bi on n-GaAs substrates [9]:…”

“…Among the different growth techniques, electrodeposition appears as the most suitable to grow Bi since it is a fast procedure to obtain high quality layers on different substrates ( [9] and references therein). Also important to remark, it is a cost-effective growth method compatible with patterning and transferable to industry.…”

“…We showed the strong impact that the growth overpotential has on the properties of Bi layers electrodeposited at constant potential on Hads-free highly doped n-GaAs(111)B substrates [11,9]. We reported that the morphological, structural and interfacial electrical properties are clearly correlated with the nucleation process which is in turn correlated with the energy band diagram of the semiconductor-electrolyte interface (SEI).…”

Influence of Bi on dielectric properties of GaAs1−xBix alloys

“…In the literature [7,8], several works have been focused on the study of the impact of laser irradiation on GaAsBi/GaAs quantum wells, band structure, photovoltaic characterization, structural and electronic properties of GaAsBi. The effect of Bi in Bi-doped GaAs barrier layers on the structural and optical properties of * E-mail: deger@istanbul.edu.tr InAs/GaAs quantum-dot heterostructures has been studied [9], while the study on the correlation between overpotential and nucleation process, nucleation process and structural, electrical properties has been reported in another works [10,11]. Besides, the nonlinear optical properties of GaAsBi semiconductor have been reported in the literature [12].…”