Concerted Electrodeposition and Alloying of Antimony on Indium

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Concerted Electrodeposition and Alloying of Sb on Indium Electrodes for Selective Formation of Crystalline Indium Antimonide Eli Fahrenkrug, Jessica Rafson, Mitchell Lancaster, and Stephen Maldonado Langmuir, Just Accepted Manuscript • DOI: 10.1021/acs.langmuir.7b00645 • Publication Date (Web): 07 Apr 2017 Downloaded from http://pubs.acs.org on April 8, 2017

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Concerted Electrodeposition and Alloying of Sb on Indium Electrodes for Selective Formation of Crystalline Indium Antimonide Eli Fahrenkrug,1 Jessica Rafson,1 Mitchell Lancaster,1 and Stephen Maldonado1,2* 1) Department of Chemistry 2) Program in Applied Physics University of Michigan 930 N. University Ann Arbor, MI 48109-1055 Abstract. The direct preparation of crystalline indium antimonide (InSb) by the electrodeposition of antimony (Sb) onto indium (In) working electrodes has been demonstrated. When Sb is electrodeposited from dilute aqueous electrolytes containing dissolved Sb2O3, an alloying reaction is possible between Sb and In if any surface oxide films are first thoroughly removed from the electrode. The presented Raman spectra detail the interplay between the formation of crystalline InSb and the accumulation of Sb as either amorphous or crystalline aggregates on the electrode surface as a function of time, temperature, potential, and electrolyte composition. Electron and optical microscopies confirm that under a range of conditions, the preparation of a uniform and phase-pure InSb film is possible. The cumulative results highlight this methodology as a simple yet potent strategy for the synthesis of intermetallic compounds of interest.

*[email protected]

ACS Paragon Plus Environment

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Introduction. Several chemical and electrochemical strategies are known for the preparation of inorganic semiconductors,1-3 each with specific advantages and disadvantages. A specific challenge in electrodeposition strategies is the ability to prepare semiconductor films rapidly that are simultaneously thick and crystalline as-prepared. Our group has started to explore the concept of combining an alloying reaction with freshly electrodeposited species to form new phases and/or compounds.4-7 The appeal of this approach is that it synergizes the synthetic power of metallurgical reactions with the control over heterogeneous reaction rates inherent in electrochemical reactions. Although prevalent in the context of rechargeable batteries,8 amalgam formation,9,10 and with some analogy to the concept of underpotential deposition,11 the intentional reaction of an electrodeposited species with the underlying metal electrode has not been extensively explored for the purpose of producing technologically relevant III-V semiconductors. Indium antimonide (InSb) is one such target material, with extremely high carrier mobilities and a small bandgap suitable for sensing (e.g. photodetectors12) and energy (lattice matched substrates for CdTe photovoltaics,13,14 IR absorbers in thermophotovoltaics15) technologies. Building off our prior demonstrations of hybrid electrodeposition-alloying reaction syntheses of crystalline InAs, GaAs, and GaSb,4-6 we are interested in the synthesis of InSb as a further test of the electrochemically-controlled alloy reaction concept since InSb has a negative free energy of formation at room temperature (-25.3 kJ mol-1 at T = 300 K)16 and Sb can be electrodeposited from aqueous solutions. Therefore a simple alloying reaction between zero valent In and Sb to form InSb should be spontaneous and strongly favored at room temperature (eq 1) when Sb is electrodeposited on indium electrodes.

In 0 + Sb 0 → InSb ( s )

(1)

Herein, this report presents a series of spectroelectrochemical experiments where the chemistry at an indium electrode interface is monitored by Raman spectroscopy to identify any evidence for eq 1. Raman is ideal for these studies because it is naturally compatible with aqueous electrolytes and also yields unique and identifiable spectral signals for crystalline InSb,17 amorphous InSb,18 crystalline Sb,19 and amorphous Sb.20 Raman spectroscopy is particularly well suited to the early stages of InSb film formation,17,20 where the total thickness precludes or substantially


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complicates analysis by X-ray diffraction. In addition, optical and electron microscopy data are presented to identify unambiguously conditions where InSb is formed directly through eq 1. Experimental. Chemicals and Materials Indium foil (0.127 mm thick, 99.99%) was obtained from Alfa Aesar. Powdered antimony (III) oxide (Sb2O3(s), 99%, Sigma-Aldrich), antimony (III) chloride (SbCl3, >99.95%, Sigma-Aldrich), concentrated H2SO4 (95-98%, Sigma-Aldrich) and NaOH (98%, Fisher) were used as received. Water with a resistivity >18 MΩ cm was obtained from a Barnstead Nanopure III purification system. Electrochemical Experiments A CHI760C (CH Instruments) potentiostat was used for electrochemical experiments. All experiments were performed in a deaerated glass electrochemical cell with a three electrode configuration featuring a section of indium foil contacted with a 24 gauge copper wire by silver print (GC Electronics) that was dried at 40 °C for 30 min.. These assemblies were threaded through a glass tube (diameter = 0.25 in) and embedded in inert epoxy (Hysol 1C), exposing only indium. All indium electrodes had a wettable area of 0.5 to 1.0 cm2. A Pt mesh electrode (area = 2 cm2) and Ag/AgCl electrode were used as the counter and reference, respectively. All potentials are reported with respect to E(Ag/AgCl, sat. KCl). Galvanic experiments corresponded to unbiased indium foil electrodes immersed in deaerated electrolytes. Prior to use, all indium electrodes were cleaned by immersion/sonication in separate volumes of acetone (1 min), methanol (1 min), dichloromethane (30 s), methanol (1 min), and water (1 min). Electrodes were used for study immediately thereafter. Materials Characterization High-resolution transmission electron microscopy (HRTEM) and selected area electron diffraction (SAED) measurements were performed with a JEOL 3011 TEM equipped with a LaB6 electron source held at 300 keV. Samples were prepared by first gently scraping any surface off the indium foil working electrodes with a glass pipet tip. The collected film was dispersed in < 500 µL of CH3OH (190 proof, ACS spectrophotometric grade, Aldrich) and sonicated for up to 60 s. Aliquots with 3 µL volumes were then cast over a TEM grid coated with an ultrathin carbon support (400 mesh copper, Ted Pella). All Raman spectra were obtained with a Renishaw RM series Raman microscope equipped with a Nikon LU Plan 20x objective (NA = 0.4), a 785 diode laser, edge filters to reject the 785 nm Rayleigh scatter, and no polarizing optics. The excitation source and CCD detector (578 x 400) were positioned in 180° backscatter geometry. Unless indicated otherwise, the total radiant power to the


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sample during spectral acquisition was < 1.12 mW over a 20 µm2 spot. For steady-state spectra, each spectral acquisition was integrated for 30 s and then scan averaged three times. All reported spectra represent the typical responses observed over at least 10 different spots. A custom Pyrex cell with a quartz viewing window that can accommodate horizontally positioned electrodes designed to fit within the working distance (WD = 13 mm) of the objective was used to collect time-dependent insitu Raman spectra. For in-situ studies, ten spectra (10 s per acquisition, 0.8 s delay between acquisitions) were averaged at each time point. The same optical microscope was used to collect photographs for representative samples. All spectra are presented with y-axes normalized to the highest collected counts in each raw spectrum.

Results. Figure 1 shows representative cyclic voltammetric responses for indium foil electrodes immersed in alkaline (NaOH, pH = 13.8) aqueous solutions containing varied amounts of dissolved Sb2O3. In this electrolyte, SbO2- is the dominant Sb-containing species.21 In the absence of any dissolved Sb2O3, the voltammetric response between -0.75 V and -2.05 V contained two distinctive features for as-prepared indium electrodes (Figure 1a). The first feature was a persistent set of voltammetric waves near -1.15 V corresponding to the quasi-reversible cathodic removal/anodic formation of a surface oxide.22,23 This redox feature was broadly consistent with the standard potential for the redox of stoichiometric indium oxide (i.e. E(In2O3/In) = -1.19 V)21 in this electrolyte (eq 2), implying 3+ redox state of indium in the surface oxide.

In 2O 3 ( s ) + 3H 2 O + 6e −  → 2In( s ) + 6OH − (aq )

(2)

The cathodic and anodic peaks were notably sharper (full width at half maximum ≤ 11 mV) than similar voltammetry reported for indium electrodes in less alkaline electrolytes.23 The peak separation in Figure 1b increased with faster scan rates, indicating some ohmic resistance across the native oxide in accord with Mueller’s passivation model for thin oxide films.24 However, the dependence of the cathodic peak current with scan rate was linear, in line with predicted stripping responses for adsorbed species. At potentials more negative than E = -1.2 V, the second primary feature was the evolution of H2(g) from H+ electroreduction. The steady-state current density for this process reached 2 mA cm-2 at -2.0 V.


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Upon the addition of dissolved Sb2O3, a mass-transport limited peak at -1.05 V for the 3ereduction to Sb0 (E(SbO2-/Sb) = -0.90 V)21 was observed (Figure 1c, eq 3).

SbO 2− (aq ) + 2H 2 O + 3e −  → Sb( s ) + 4OH − (aq )

(3)

Notably, the presence of dissolved Sb2O3 did not substantially perturb the cathodic removal/anodic formation of the native oxide on indium, but residual current was higher on the cathodic scan after the reduction of the oxide film. For 1 mM dissolved Sb2O3, the ~0.2 mA cm-2 current at E = -1.28 V corresponded to a a Sb flux of ~7 x 10-13 mol cm-2 s-1. At more negative potentials, the measured currents were much higher, with a third cathodic peak more negative than E = -1.85 V consistent with the formation of stibine (SbH3(g), E(Sb/SbH3) = -1.47 V).21

Sb( s ) + 3H 2 O + 3e −  → SbH 3 ( g ) + 3OH − (aq )

(4)

The cumulative voltammetry defined three distinct potential ranges in the alkaline electrolytes (Figure 1a): (1) Sb2O3 is electroreduced on the native oxide of indium at -0.90 V > E1 > -1.19 V, (2) Sb2O3 is electroreduced on oxide-free indium at -1.19 V > E2 > -1.47 V, and (3) Sb0 is removed from the electrode through the formation of gaseous stibine at E3 < -1.47 V. Figure 2 shows Raman spectra collected for indium electrodes immersed in an electrolyte containing 0.6 M NaOH(aq) and 1 mM of dissolved Sb2O3. Figure 2a shows the spectra as a function of time while the electrode was stepped to E = -1.10 V. The electrode changed appearance, becoming unevenly coated with dark spots, as shown in Figures 3a and 3b. Raman spectra were collected all over the indium electrodes but only the opaque regions yielded spectra that differed from blank measurements on dry indium foil. At short times (t < 3 min), no signals above the background were observed. At t = 6 min, a peak at 150 cm-1 was noted that became more prominent at t = 10 min. Another peak at 113 cm-1 was also apparent at t = 10 min. These features were consistent with the Raman-active phonon modes for crystalline Sb0 at 110 and 149.8 cm-1 (denoted as Eg and A1g, respectively).19 Figure 2b shows analogous Raman measurements when an indium electrodes is stepped to E = -1.28 V. In these experiments, the electrode surface was coated with a dull film uniformly. Spectra obtained everywhere on the electrode showed a broad wave centered at 141 cm-1 was apparent after less than 3 min, consistent with the Raman-active mode for amorphous Sb0.20 At long times, this broad feature increased in intensity and no additional peaks were observed.


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Figure 4 shows Raman spectra collected for indium electrodes immersed in the same alkaline electrolyte with varied amounts of dissolved Sb2O3 after t = 10 min. Figure 4a shows that at E = -1.10 V, the most dilute levels of dissolved Sb2O3 yielded Raman spectra with no signals above the background. At increasing concentrations of dissolved Sb2O3, the Raman spectra showed features of amorphous and then crystalline Sb. However, Figure 4b shows the analogous experiments yielded different spectra when the electrode was held at E = -1.28 V. At formal concentrations of Sb2O3 of 0.1 mM and 0.5 mM, the Raman spectra showed a prominent peak at 175 cm-1 with a very slight shoulder at larger Raman shifts, in agreement with the transverse optical (TO) and longitudinal optical (LO) phonon modes for crystalline InSb.18 However, at the higher concentration of 1 mM, this Raman signal disappeared and the same broad wave at 141 cm-1 corresponding to amorphous Sb was prominent. Figure 5a shows an optical photograph of indium foils that produced Raman features consistent with crystalline InSb as in Figure 4b. These electrodes were uniformly pale yellow-gold without any dark spots. Upon removal, these films showed direct evidence of crystallinity in transition electron micrographs (Figure 5b). Lattice fringes were observed on films sections with > 5 nm thickness that had a spacing of 0.36 ± 0.01 nm, consistent with the d spacing along the [111] direction of zinc blende InSb.25 These film sections were further probed by selected area electron diffraction and yielded patterns as shown in Figure 5c. Concentric rings rather than discrete spots were routinely collected, implying the beam probed multiple, randomly oriented crystallites rather than a single crystal. However, the number and ratio of the diameters of the rings did not match the known diffraction patterns for crystalline In2O3, In, or Sb. Instead, these data could only be indexed to crystalline InSb. Attempts were made to increase the total amount of InSb produced by controlled electrodeposition of Sb onto oxide-free indium foil electrodes. Figure 6 shows that merely increasing the hold time for the potential step does not yield appreciably thicker quantities of InSb (as inferred from the apparent signal-to-noise ratio of the Raman spectrum). Instead, longer times yielded Raman spectra showing again the broad feature of amorphous Sb centered at 141 cm-1. The slight shoulder at 178 cm-1 for t = 2 h suggests that perhaps the InSb TO mode was formed but was subsequently overcoated by a film of amorphous Sb that blocked any Raman scatter. Experiments were repeated with more negative electrode potentials. Figure 7 shows Raman spectra collected for indium electrodes immersed in an alkaline electrolyte containing 0.1 mM dissolved Sb2O3 and held for t = 10 min at the designated potentials. Although the Raman feature for crystalline InSb was observed at more negative potentials, the similar signal-to-noise ratio (S/N) of ~


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5 in the raw spectra suggested that a similar amount of InSb was deposited. A further set of experiments were attempted employing the highest concentration of dissolved Sb2O3. As before, potentials in regions 1 and 2 (as defined in Figure 1a) yielded either no deposit, amorphous Sb, or crystalline Sb. However, applied potentials in region 3 showed a strong Raman peak for crystalline InSb. At E = -1.56 V, the Raman spectra also showed a very broad peak at lower Raman shifts that appeared to be a convolution of the Raman modes for amorphous and crystalline Sb. At E = -1.85 V, the Raman spectra showed only the peak for crystalline InSb with a S/N value of 86. These electrodes appeared uniformly dark but without any apparent particles or change to the original surface texture of the indium foil. A final set of experiments were performed to determine the influence of temperature. Figure 8 shows Raman spectra collected as in Figure 7b at E = -1.85 V as a function of the temperature of the indium electrode during deposition. The collected spectra all showed the same principle TO mode for crystalline InSb. At the highest temperature of 80 °C, a shoulder consistent with the LO mode was more prominent. Analogous experiments performed at E = -1.28 V only showed the increased prominence of the peak for crystalline Sb over amorphous Sb, but still no InSb (Supporting Information, Figure S1). An additional set of control experiments was performed where an indium electrode coated with a thin amorphous Sb film was heated dry and in air at various temperatures up to T = 250 °C for 10 min each (Supporting Information, Figure S2). Raman spectra collected for these samples also showed conversion of amorphous Sb to crystalline Sb but no signal for crystalline InSb. Discussion. General Observations This work represents the fourth distinct system where a crystalline binary material is synthesized by a sequential electrodeposition of a group V element and a following alloying reaction. In accord with the prior observations for InAs,5 GaAs,4 and GaSb,6 three general themes were clear: (1) the reaction critically hinged on the removal of the surface oxide, (2) accumulation of Sb0 occurs when the deposition outpaces the alloying reaction with In0, and (3) Sb0 can be selectively removed at large overpotentials to yield thicker and homogeneous InSb films. These points are summarized in Scheme 1 and are discussed below. First, removal of the native surface oxide on the metal electrode is essential. Even though the passivating oxide film was sufficiently thin that electroreduction of dissolved Sb2O3 was possible in potential range 1, no evidence for InSb (crystalline or otherwise) was observed. This fact necessarily implies that diffusion of Sb0 through the native oxide was vanishingly slow in the temperature range


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investigated here. Conversely, when the oxide was cathodically stripped off in potential ranges 2 and 3, the production of InSb necessarily implied that In and Sb were in intimate/direct contact. This point is obvious in the context of nuclei formed during electrodeposition, but not in the context of a metallurgical reaction between two elements that are readily oxidized in air and water. That is, even while submerged in water, zero valent In and zero valent Sb are stable enough to react. This notion is in stark contrast with reaction conditions usually employed for vapor phase InSb film deposition26-29 or more general alloying reactions between two thin metal films in vacuum.30,31 From a materials science perspective, the traditional requirements of either high temperatures, extensive vacuum technology, or strongly reducing gases to effect a non-oxidizing environment are entirely obviated just by a sufficiently negative applied potential. Second, the data collected in potential range 2 indicates there are at least two parallel chemical reaction pathways available to Sb0 at the indium electrode surface. Assuming that the initial stages of Sb electrodeposition nucleates only on indium surface sites (i.e. produces discrete Sb0 adatoms), then each new Sb0 species could migrate to its n nearest neighbor and form Sbn clusters.

nSb → Sb n

(5)

The local order, size, and orientations of Sb clusters are determined by several factors but clearly the data here show that both amorphous and crystalline Sb readily form under the employed conditions. Although an alloying reaction between large Sbn clusters and In is possible at higher temperatures as demonstrated by previous studies of annealed thick films of In on Sb,32 the extent and efficiency of the alloying reaction presented here depends critically on the Sb0 not accumulating. Control experiments where amorphous Sb films were deposited on In and then separately annealed in an oven up to T = 250 °C did not show any evidence of InSb in the timescales (101 min) used here. The alloying reaction between In0 and Sb0 (eq 1) represents the alternative to eq 5 for Sb0 adatoms. The initial rate of this reaction should only be governed by the kinetics of In-Sb bond formation. The fact that InSb was readily detected indicates this rate is at least comparable to the rate of eq 5 for Sb0 adatoms. However, as Sb0 is depleted from the electrode/electrolyte interface through the formation of InSb, the predominant form of Sb on the surface depends on the rate of transport of new reactants. Sb0 adatoms are constantly replenished by electroreduction of Sb2O3 but have to diffuse through InSb to react with In0 below the solid/electrolyte interface. Alternatively, In0 atoms from the bulk could diffuse through InSb to react with new Sb0 adatoms. The diffusivities of Sb0 and


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In0 in crystalline InSb are comparable,33,34 suggesting either scenario (or a combination of the two) are possible. Diffusion rather than electromigration35 is more likely the dominant mode of reactant transport as the Raman intensities for the crystalline InSb signal in Figure 7a did not change noticeably with overpotential. Diffusion as the limiting factor in the rate of InSb formation is supported by two separate observations. First, the data in Figure 6 indicated that at long times, and even at potentials in range 2, the deposition of pure Sb eventually outpaces the formation of InSb. This would be expected as thicker amounts of InSb would represent longer transit times of reactants before reaching the reactive interface. Second, the LO phonon mode for crystalline InSb increases at higher temperatures in Figure 8. This feature indicates the InSb crystal domain size increased,20 consistent with faster diffusion at higher temperatures that allows eq 1 to continue to a greater extent. Third, the data collected in potential range 3 shows that extreme negative potentials can be used to selectively remove excess Sb0 and render a 'clean' InSb film. This tunability is generally not possible in alloying reactions between solids or alloying preceded by deposition of reactant from the vapor phase. A similar approach has been used in electrodeposition by electrochemical atomic layer epitaxy36 to reductively dissolve group VI elements as anions. Here, the formation of the hydride (stibine) effectively eliminates any Sb that accumulates on the electrode surface. The advantage of this approach is that it is non-destructive towards InSb. However, it also necessarily implies a disadvantage regarding faradaic efficiency for the preparation of InSb from SbO2- reduction at very negative potentials. That is, deposition of InSb in potential range 3 necessarily ‘wastes’ charge since some of the electroreduced Sb is removed and not efficiently reacted with In to form InSb. Comparison to Related Processes Several reports detail electrodeposition of InSb through simultaneous reduction of oxidized In and Sb salts in a variety of different solvents.37-42 Rapid material synthesis is possible in this way but control over the stoichiometry, purity, and crystallinity of the as-deposited InSb is challenging. For example, although the rates of reduction for both oxidized salts can in principle be balanced at a specific set of parameters (i.e. temperature, potential, concentration), such conditions are difficult to identify a priori. Anomalous co-deposition or induced underpotential deposition phenomenon are common,43 where the nucleation of one element necessarily affects the electroreduction of the other element. In contrast, the control afforded in the method of this work is clear. The trade-off is the limited amount of material that can be generated. Alloying reactions limited by diffusion will be necessarily slow at low temperatures. Accordingly, changing solvents from water to a higher boiling point liquid may enable the deposition of thicker InSb films. Two caveats in the replacement of water


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are that the new solvent must still allow the facile electrochemical removal of the native oxide and should still enable gasification of excess Sb. These conditions probably preclude the use of many aprotic organic solvents, but perhaps molten salts or ionic liquids42,44,45 are still useful. If so, then it may be possible convert a more appreciable fraction of the indium electrode volume to InSb, akin to chemical conversion of metals to metal phosphides by reaction with organophosphines at high temperature.46 The advantage in the electrochemical-alloying approach is that the metallurgical reaction is controlled by the details of the electrodeposition process. This aspect is underscored by separate galvanic (i.e. no applied potential) experiments with indium foils immersed in acidic electrolyte containing dissolved SbCl3 (Supporting Information, Figure S3). At low pH, Sb0 was spontaneously deposited on indium electrodes at open circuit since the native oxide on indium is soluble and the In/In2O3 couple has a more negative standard potential than the reduction of HSbO2 (the dominant Sb species in acid).21 In these control experiments, Raman spectra indicated that although InSb films were produced with dilute HSbO2, there was always some appreciable amount of amorphous Sb0 because there was no precise way to slow the flux. Paths Forward Despite the low boiling temperature of water, there is still potential utility in producing thin films of InSb in aqueous electrolytes. Ultra-thin films of InSb are highly desirable for magnetoresistive, spintronic, and IR sensors.47,48 Although thin InSb can be prepared through electrochemical atomic layer epitaxy,49,50 the approach advocated here eliminates the need for only using substrates that enable underpotential deposition. Preparing thin InSb films through vapor phase methods is similarly problematic because the large lattice mismatch of InSb with most substrates of interest, e.g GaAs and Si, results in discrete nuclei rather than films.47,48 In contrast, deposition of conformal thin metal films on these substrates is straightforward through conventional electrodeposition, electroless plating, metal evaporation, and sputtering. We surmise that if a continuous thin film of In were first deposited by an aforementioned process, then controlled electrodeposition of Sb followed by alloying as shown here may enable complete conversion to contiguous, large area films of InSb on any substrate of interest. Moreover, if the thin indium films were first lithographically patterned, then InSb disks, wires, dots…etc. ought to be readily realizable. Still, more work is needed to determine what factors will affect the crystalline orientation(s) and electronic properties of such materials. For instance, it is not clear what governs the crystal size in this process and if the crystalline domain size of the product material (InSb) has any relation to the grain size in the pristine indium foil. For that matter, it would be prudent to know if more metal antimonide compounds can be made in this way. A number of binary antimonides have similar or


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even more negative free energies of formation,16 suggesting the same sequential electrodepositionalloying scheme ought to be more broadly applicable. More work is needed on this front. Conclusions. This work demonstrates another example where electrodeposition can be utilized in concert with a metallurgical reaction to form targeted crystalline material of interest. Here, the data show that when a buffering, native oxide is removed from a polycrystalline indium electrode, the interface is sufficiently reactive to alloy with freshly electrodeposited Sb0 to form crystalline InSb at room temperature. If the oxide is not removed, no metallurgical reaction occurs at ambient conditions and the result is either amorphous coatings or discontinuous films of crystalline Sb. Two specific routes were identified for crystalline InSb. First, a moderate overpotential could be applied to selectively and to slowly grow InSb, balancing the effective rates of Sb nucleation on the surface, the reaction kinetics for In0 bonding to Sb0, and the diffusivity of Sb through solid In and InSb. Second, selectivity for InSb can be sacrificed for faster InSb formation by removing excess Sb0 through gasification into SbH3. The shared interesting features of these general approaches are that variations in electrolyte composition and applied potential, in addition to temperature, strongly impact the form of the product, affording more experimental control than available in purely solid-state metallurgical reactions. These aspects motivate both the specific use of this method for device structures that employ crystalline InSb and the more general development of this electrochemical-controlled metallurgy as a materials synthetic methodology.

Supporting Information Additional details including temperature-dependent Raman spectra and optical images of indium foils after galvanic treatment in acidic solutions containing Sb2O3 are presented in the Supporting Information. This material is available free of charge via the internet at http://pubs.acs.org. The authors declare no competing financial interest. Acknowledgments This work was supported by the National Science Foundation (CHE-1505635). E.F. also acknowledges a University of Michigan Rackham Doctoral Fellowship. The JEOL 3011 TEM used in this work is maintained by the Michigan Center for Materials Characterization through NSF


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support (DMR-0315633). J. R. acknowledges the NSF REU program (CHE-1460990). D. M. and Q. C. are acknowledged for helpful discussions.


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References. 1. Lincot, D. "Electrodeposition of semiconductors" Thin Solid Films 2005, 487, 40-48. 2. Schlesinger, M. E.; Rajeshwar, K.; De Tacconi, N. R. "Electrodeposition of Semiconductors" In Modern Electroplating; 5th ed.; Schlesinger, M. E., Paunovic, M., Eds.; John Wiley & Sons, Inc.: 2010. 3. Switzer, J. A. "Electrodeposition at the Nanoscale" In Nanoelectrochemistry; Mirkin, M. V., Amemiya, S., Eds.; CRC Press: 2015. 4. Fahrenkrug, E.; Gu, J.; Maldonado, S. "Electrodeposition of Crystalline GaAs on Liquid Gallium Electrodes in Aqueous Electrolytes" J. Am. Chem. Soc. 2013, 135, 330-339. 5. Fahrenkrug, E.; Gu, J.; Maldonado, S. "Electrochemically Gated Alloy Formation of Crystalline InAs Thin Films at Room Temperature in Aqueous Electrolytes" Chem. Mater. 2014, 26, 4535-4543. 6. DeMuth, J.; Ma, L.; Fahrenkrug, E.; Maldonado, S. "Electrochemical Liquid-Liquid-Solid Deposition of Crystalline Gallium Antimonide" Electrochim. Acta 2016, 197, 353-361. 7. Fahrenkrug, E.; Maldonado, S. "Electrochemical Liquid-Liquid -Solid (ec-LLS) Crystal Growth: A Low - Temperature Strategy for Covalent Semiconductor Crystal Growth" Acc. Chem. Res. 2015, 48, 1881-1890. 8. Goodenough, J. B.; Kim, Y. "Challenges for Rechargeable Li Batteries†" Chem. Mater. 2010, 22, 587603. 9. Kemula, W.; Galus, Z.; Kublik, Z. "Application of the Hanginig Mercury Drop Electrode to an Investigation of Intermetallic Compounds in Mercury" Nature 1958, 182, 1228-1229. 10. Galus, Z.; Meites, L. "Electrochemical Behaviors of Metal Amalgams" CRC Critical Reviews in Analytical Chemistry 2008, 4, 359-422. 11. Herrero, E.; Buller, L. J.; Abruna, H. D. "Underpotential Deposition at Single Crystal Surfaces of Au, Pt, Ag, and Other Materials" Chem. Rev. 2001, 101, 1897-1930. 12. Guo, N.; Hu, W. D.; Chen, X. S.; Lei, W.; Lv, Y. Q.; Zhang, X. L.; Si, J. J.; Lu, W. "Optimization for mid-wavelength InSb infrared focal plane arrays under front-side illumination" Optical and Quantum Electronics 2013, 45, 673-679. 13. Song, T.; Kanevce, A.; Sites, J. R. In Photovoltaic Specialist Conference; IEEE: 2015. 14. DiNezza, M. J.; Zhao, X.-H.; Liu, S.; Kirk, A. P.; Zhang, Y.-H. "Growth, steady-state, and timeresolved photoluminescence study of CdTe/MgCdTe double heterostructures on InSb substrates using molecular beam epitaxy" Appl. Phys. Lett. 2013, 103, 193901. 15. Krier, A.; Yin, M.; Marshall, A. R. J.; Krier, S. E. "Low Bandgap InAs-Based Thermophotovoltaic Cells for Heat-Electricity Conversion" J. Electron. Mater. 2016, 45, 2826-2830. 16. Schlesinger, M. E. "Thermodynamic properties of solid binary antimonides" Chem. Rev. 2013, 113, 8066-8092. 17. Wagner, V.; Drews, D.; Esser, N.; Zahn, D. R. T.; Geurts, J.; Richter, W. "Raman monitoring of semiconductor growth" J. Appl. Phys. 1994, 75, 7330-7333. 18. Wang, X.; Kunc, K.; Loa, I.; Schwarz, U.; Syassen, K. "Effect of pressure on the Raman modes of antimony" Phys. Rev. B 2006, 74, 134305. 19. Lannin, J. S.; Calleja, J. M.; Cardona, M. "Second-order Raman scattering in the group-Vb semimetals: Bi, Sb, and As" Phys. Rev. B 1975, 12, 585-593. 20. Rettweiler, U.; Richter, W.; Resch, U.; Geurts, J.; Sporken, R.; Xhonneux, P.; Caudano, R. "Epitaxial InSb(111) layers on Sb(111) substrates characterised by Raman spectroscopy" J. Phys.: Condens. Matter 1989, 1, SB93-SB97. 21. Pourbaix, M. Atlas of Electrochemical Equilibria in Aqueous Solutions; 2nd ed.; National Association of Corrosion Engineers: Houston, TX, 1974. 22. Butler, J. N.; Dienst, M. "Hydrogen Evolution at a Solid Indium Electrode" J. Electrochem. Soc. 1965, 112, 226-232. 23. Omanović, S.; Metikoš-Huković, M. "Thin oxide films on indium: impedance spectroscopy investigation of reductive decomposition" Thin Solid Films 1995, 266, 31-37.


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24. Kapusta, S. D.; Hackerman, N. "Anodic passivation of tin in slightly alkaline solutions" Electrochim. Acta 1980, 25, 1625-1639. 25. Herren, G.; Walsoe de Reca, N. E. "Intercalation of Lithium in InSb" Solid State Ionics 1991, 47, 5761. 26. Okamoto, A.; Yoshida, T.; Muramatsu, S.; Shibasaki, I. "Magneto-resistance effect in InSb thin film grown using molecular beam epitaxy" J. Cryst. Growth 1999, 201/202, 765-768. 27. Kanisawa, K.; Yamaguchi, H.; Hirayama, Y. "Two-dimensional growth of InSb thin films on GaAs(111)A substrates" Appl. Phys. Lett. 2000, 76, 589-591. 28. Senthilkumar, V.; Venkatachalam, S.; Viswanathan, C.; Gopal, S.; Narayandass, S. K.; Mangalaraj, D.; Wilson, K. C.; Vijayakumar, K. P. "Influence of substrate temperature on the properties of vacuum evaporated InSb films" Cryst. Res. Technol. 2005, 40, 573-578. 29. Paul, R. K.; Penchev, M.; Zhong, J.; Ozkan, M.; Ghazinejad, M.; Jing, X.; Yengel, E.; Ozkan, C. S. "Chemical vapor deposition and electrical characterization of sub-10nm diameter InSb nanowires and field-effect transistors" Mater. Chem. Phys. 2010, 121, 397-401. 30. Kozlov, V. M.; Bozzini, B.; Peraldo Bicelli, L. "Preparation of InAs by annealing of two-layer In–As electrodeposits" J. Alloys Compd. 2004, 366, 152-160. 31. Hentzell, H. T. G.; Thompson, R. D.; Tu, K. N. "Interdiffusion in copper–aluminum thin film bilayers. I. Structure and kinetics of sequential compound formation" J. Appl. Phys. 1983, 54, 6923-6928. 32. Kozlov, V. M.; Agrigento, V.; Bontempi, D.; Canegallo, S.; Moraitou, C.; Toussimi, A.; Bicelli, L. P.; Serravalle, G. "Intermetallic compound formed by electrodeposition of indium on antimony" J. Alloys Compd. 1997, 259, 234-240. 33. Eisen, F. H.; Birchenall, C. E. "Self-diffusion in indium antimonide and gallium antimonide" Acta Metall. 1957, 5, 265-274. 34. Kendall, D. L.; Huggins, R. A. "Self‐Diffusion in Indium Antimonide" J. Appl. Phys. 1969, 40, 27502759. 35. Reddy, K. V.; Prasad, J. J. B. "Electromigration in indium thin films" J. Appl. Phys. 1984, 55, 15461550. 36. Gu, J.; Zhang, K.; Maldonado, S. "Analysis of the Electrodeposition and Surface Chemistry of CdTe, CdSe, and CdS Thin Films through Substrate-Overlayer Surface Enhanced Raman Spectroscopy" Langmuir 2014, 30, 10344-10353. 37. McChesney, J.-J.; Haigh, J.; Dharmadasa, I. M.; Mowthorpe, D. J. "Electrochemical growth of GaSb and InSb for applications in infra-red detectors and optical communication systems" Opt. Mater. 1996, 6, 63-67. 38. Fulop, T.; Bekele, C.; Landau, U.; Angus, J.; Kash, K. "Electrodeposition of polycrystalline InSb from aqueous electrolytes" Thin Solid Films 2004, 449, 1-5. 39. Hnida, K.; Mech, J.; Sulka, G. D. "Template-assisted electrodeposition of indium–antimony nanowires – Comparison of electrochemical methods" Appl. Surf. Sci. 2013, 287, 252-256. 40. Kuo, C.-H.; Wu, J.-M.; Lin, S.-J. "Room temperature-synthesized vertically aligned InSb nanowires: electrical transport and field emission characteristics" Nanoscale Research Letters 2013, 8, 69. 41. Hnida, K. E.; Bäßler, S.; Mech, J.; Szaciłowski, K.; Socha, R. P.; Gajewska, M.; Nielsch, K.; Przybylski, M.; Sulka, G. D. "Electrochemically deposited nanocrystalline InSb thin films and their electrical properties" Journal of Materials Chemistry C 2016, 4, 1345-1350. 42. Hsieh, Y.-T.; Chen, Y.-C.; Sun, I.-W. "Electrodeposition of Stoichiometric Indium Antimonide from Room-Temperature Ionic Liquid 1-Butyl-1-Methylpyrrolidinium Dicyanamide" ChemElectroChem 2016, 3, 638-643. 43. Mosby, J. M.; Johnson, D. C.; Prieto, A. L. "Evidence of induced underpotential deposition of crystalline copper antimonide via instantaneous nucleation" J. Electrochem. Soc. 2010, 157, E99-E105. 44. Endres, F. "Ionic liquids: Solvents for the electrodeposition of metals and semiconductors" ChemPhysChem 2002, 3, 144-154.


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45. Yang, M.-H.; Yang, M.-C.; Sun, I.-W. "Electrodeposition of indium antimonide from the waterstable 1-ethyl-3-methylimidazolium chloride/tetrafluoroborate ionic liquid" J. Electrochem. Soc. 2003, 150, C544-C548. 46. Henkes, A. E.; Schaak, R. E. "Trioctylphosphine: A General Phosphorus Source for the LowTemperature Conversion of Metals into Metal Phosphides" Chem. Mater. 2007, 19, 4234-4242. 47. Zhang, T.; Clowes, S. K.; Debnath, M.; Bennett, A.; Roberts, C.; Harris, J. J.; Stradling, R. A.; Cohen, L. F.; Lyford, T.; Fewster, P. F. "High-mobility thin InSb films grown by molecular beam epitaxy" Appl. Phys. Lett. 2004, 84, 4463-4465. 48. Debnath, M. C.; Mishima, T. D.; Santos, M. B.; Phinney, L. C.; Golding, T. D.; Hossain, K. "High electron mobility in InSb epilayers and quantum wells grown with AlSb nucleation on Ge-on-insulator substrates" J. Vac. Sci. Technol., B 2014, 32, 02C116. 49. Wade, T. L.; Vaidyanathan, R.; Happek, U.; Stickney, J. L. "Electrochemical formation of a III-V compound semiconductor superlattice: InAs/InSb" J. Electroanal. Chem. 2001, 500, 322-332. 50. Vaidyanathan, R.; Cox, S. M.; Happek, U.; Banga, D.; Mathe, M. K.; Stickney, J. L. "Preliminary studies in the electrodeposition of PbSe/PbTe superlattice thin films via electrochemical atomic layer deposition (ALD)" Langmuir 2006, 22, 10590-5.


1.0 mM Sb2O3, 0.6 M NaOH 0.5 mM Sb2O3, 0.6 M NaOH 0.1 mM Sb2O3, 0.6 M NaOH 0.6 M NaOH

10 1

2

3

0 -1.0

-1.4

-1.8

Potential /V vs. Ag/AgCl

0.5

b)

0.0

-0.5

Page 16 of 25

Fit

0.6 0.4 0.2 0.0 0

-1.0

5

10

15

20

20 mV s-1 10 mV s-1 5 mV s-1 4 mV s-1 3 mV s-1 2 mV s-1 1 mV s-1 0.5 mV s-1

Scan Rate /mV s-1

-1.1

-1.2

-1.3


Current Density /mA cm-2

a)

Cathodic Peak Current/mA cm-2

20

Current Density /mA cm-2

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Current Density /mA cm -2

Langmuir

c) 0.9 0.0

-0.9

1.0 mM Sb2O3 0.5 mM Sb2O3 0.1 mM Sb2O3

-1.8 -1.0

-1.2

-1.4


Figure 1. a) Representative cyclic voltammetric responses of an indium foil working electrode immersed in alkaline aqueous electrolyte containing various amounts of dissolved Sb2O3. Scan Rate = 20 mV s-1; T = 22 ± 2 °C. b) Representative cyclic voltammetric responses of an indium foil working electrode immersed in 0.6 M NaOH(aq) at various scan rates. T = 22 ± 2 °C. Inset: Peak cathodic current vs scan rate. c) Same voltammetry as in (a) but focused on the potential range around the indium oxide stripping wave.


a)

E = -1.10 V [Sb2O3] = 1 mM

10 min 6 min 3 min 0 min

100

150

200

250 -1

Raman Shift /cm

Normalized Intensity /a.u.

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Langmuir


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b)

E = -1.28 V [Sb2O3] = 1 mM

10 min 3 min 0 min

100

150

200

250 -1

Raman Shift /cm

Figure 2. Representative Raman spectra collected at indium foil electrodes immersed in an alkaline aqueous electrolyte with a formal concentration of 1 mM of dissolved Sb2O3 at a potential of a) -1.10 V and b) -1.28 V for various times. T = 22 ± 2 °C. Spectra are offset for clarity.


Langmuir

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

a)

b)

Page 18 of 25

c)

Figure 3. Optical photographs of a) as-received indium foil, and c) indium foil after treatment as in Figure 2b for t = 10 min. b) indium foil after treatment as in Figure 2a for t = 10 min. Scale bars: 50 µm.


E = -1.10 V t = 10 min

a) 2

[Sb2O3] = 1.0 mM

1

[Sb2O3] = 0.5 mM [Sb2O3] = 0.1 mM [Sb2O3] = 0.0 mM

0 100

150

200

Raman Shift /cm-1

250


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Langmuir


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3

E = -1.28 V t = 10 min

b)

2

[Sb2O3] = 1.0 mM

[Sb2O3] = 0.5 mM

1

[Sb2O3] = 0.1 mM

[Sb2O3] = 0.0 mM

0 100

150

200

250

Raman Shift /cm-1

Figure 4. Representative Raman spectra collected at indium foil electrodes immersed in an alkaline aqueous electrolyte at several different formal concentrations of dissolved Sb2O3 at a potential of a) -1.10 V and b) -1.28 V. T = 22 ± 2 °C; t = 10 min. Spectra are offset for clarity.


Langmuir

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

a)

b)

Page 20 of 25

c)

111 220 311 400

Figure 5. a) Optical photograph of indium foil as treated in Figure 4b with a 0.1 mM concentration of dissolved Sb2O3. Scale bar: 50 µm. b) A representative transition electron micrograph of a film section dislodged off an indium foil as shown in (a). Scale bar: 5 nm. c) A representative selective area diffraction pattern obtained from the film in (b).


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Langmuir


Page 21 of 25

E = -1.28 V [Sb2O3] = 0.1 mM

3

t = 360 min

2

t = 120 min

t = 60 min

1 t = 10 min t = 0 min

0 100

150

200

250 -1

Raman Shift /cm

Figure 6. Representative Raman spectra collected at indium foil electrodes immersed in an alkaline aqueous electrolyte at an applied bias of -1.28 V with a 0.1 mM formal concentration of dissolved Sb2O3 for several different lengths of times. T = 22 ± 2 °C. Spectra are offset for clarity.


3

a)

t = 10 min [Sb2O3] = 0.1 mM

E = -1.85 V

2

E = -1.56 V E = -1.28 V

1 E = -1.10 V E = -0.80 V

0 100

open circuit

150

200

Raman Shift /cm-1

250


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Langmuir

Page 22 of 25

4

t = 10 min [Sb2O3] = 1.0 mM

b)

3

E = -1.85 V E = -1.56 V

2 E = -1.28 V E = -1.10 V

1

E = -0.80 V open circuit

0 100

150

200

250

Raman Shift /cm-1

Figure 7. Representative Raman spectra collected at indium foil electrodes immersed in an alkaline aqueous electrolyte at several applied biases with a formal concentrations of dissolved Sb2O3 of a) 0.1 mM and b) 1 mM for 10 min. T = 22 ± 2 °C. Spectra are offset for clarity.


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Langmuir


Page 23 of 25

E = -1.85 V [Sb2O3] = 1 mM t = 10 min

T = 80 °C

T = 60 °C

T = 40 °C T = 25 °C

100

150

200

250

Raman Shift /cm-1 Figure 8. Representative Raman spectra collected at indium foil electrodes immersed in an alkaline aqueous electrolyte at several temperatures with a formal concentration of dissolved Sb2O3 of 1 mM at an applied bias of -1.85 V for 10 min. Spectra are offset for clarity.


Langmuir

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

InOx

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Sb

-0.9 V > E1 > -1.19 V

In InSb

InOx -1.19 V > E2 > -1.47 V

In

In

In Sb

InSb

-1.47 V > E3

In

In

In SbH3 (g)

Scheme 1.


InSb

Page 25 of 25

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Langmuir

Table of Contents Graphic. InOx -0.9 V > E1 > -1.19 V

Sb

In InSb

InOx -1.19 V > E2 > -1.47 V

In

In

In Sb

InSb

-1.47 V > E3

In

In

InSb In

SbH3 (g)


Concerted Electrodeposition and Alloying of Antimony on Indium

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