Electrodeposition of Crystalline GaAs on Liquid Gallium Electrodes in Aqueous Electrolytes

Abstract

Crystalline GaAs (c-GaAs) has been prepared directly through electroreduction of As(2)O(3) dissolved in an alkaline aqueous solution at a liquid gallium (Ga(l)) electrode at modest temperatures (T ≥ 80 °C). Ga(l) pool electrodes yielded consistent electrochemical behavior, affording repetitive measurements that illustrated the interdependences of applied potential, concentration of dissolved As(2)O(3), and electrodeposition temperature on the quality of the resultant c-GaAs(s). Raman spectra indicated the composition of the resultant film was strongly dependent on both the electrodeposition temperature and dissolved concentration of As(2)O(3) but not to the applied bias. For electrodepositions performed either at room temperature or with high (≥0.01 M) concentrations of dissolved As(2)O(3), Raman spectra of the electrodeposited films were consistent with amorphous As(s). X-ray diffractograms of As(s) films collected after thermal annealing indicated metallurgical alloying occurred only at temperatures in excess of 200 °C. Optical images and Raman spectra separately showed the composition of the as-electrodeposited film in dilute (≤0.001 M) solutions of dissolved As(2)O(3)(aq) was pure c-GaAs(s) at much lower temperatures than 200 °C. Diffractograms and transmission electron microscopy performed on as-prepared films confirmed the identity of c-GaAs(s). The collective results thus provide the first clear demonstration of an electrochemical liquid-liquid-solid (ec-LLS) process involving a liquid metal that serves simultaneously as an electrode, a solvent/medium for crystal growth, and a coreactant for the synthesis of a polycrystalline semiconductor. The presented data serve as impetus for the further development of the ec-LLS process as a controllable, simple, and direct route for technologically important optoelectronic materials such as c-GaAs(s).

Electrochemically Gated Alloy Formation of Crystalline InAs Thin Films at Room Temperature in Aqueous Electrolytes

“…In fact, no voltammetric feature suggestive of a mass-transport-limited reduction of HAsO 3 2− was seen out to the cathodic window edge of water. Still, at potentials more negative than −1.2 V, the onset of current for H 2 evolution was consistently larger in the presence of dissolved As 2 O 3 than 14,22 and solid metal electrodes. 23 Both in the absence and presence of dissolved As 2 O 3 , the voltammetric responses included a sharp symmetrical wave near −1.15 V that was followed by two anodic features on the return sweep near −1.1 V (Figure 1) that showed a linear dependence with scan rate (Supporting Information, Figure S1a,b).…”

Electrochemical Liquid-Liquid-Solid Deposition of Crystalline Gallium Antimonide

“…GaAs ec-LLS. That is, the Ga electrode began to change its visible hue (to yellow) within the first 10 minutes of GaAs ec-LLS [15] while in GaSb ec-LLS the Ga electrode appeared unchanged for up to 30…”

“…An important difference between Sb and As is the fact that the former is approximately 10 5 times more soluble in Ga than the latter, as determined from the corresponding phase diagrams extrapolated to the temperatures explored here. [15,[33][34][35] The difference in the equilibrium solubility has several consequences. First, the greater solvating power of Ga towards Sb 0 means that a larger absolute concentration is needed to reach supersaturation for GaSb as compared to GaAs.…”

“…Briefly, in ec-LLS a liquid metal working electrode is used that functions both as a source of electrons for heterogeneous reductions and as a separate solvent for semiconductor crystal nucleation and growth. [15] In effect, ec-LLS couples conventional electrodeposition with melt crystal growth by using a liquid metal electrode with the ability to solubilize GaSb as the solvent to mediate crystal growth. Finite equilibrium solubilities of both Sb 0 (s) and GaSb(s) in the liquid metal permits the formation of crystalline GaSb at low temperatures.…”

Electrochemical Liquid-Liquid-Solid Deposition of Crystalline Ge Nanowires as a Function of Ga Nanodroplet Size

“…[9][10][11][12][13] By using liquid metals as the working electrode in an electrodeposition process, we have shown that electrochemically controlled semiconductor crystal growths are possible. [9][10][11][12][13] By using liquid metals as the working electrode in an electrodeposition process, we have shown that electrochemically controlled semiconductor crystal growths are possible.…”