Room-Temperature Epitaxial Electrodeposition of Single-Crystalline Germanium Nanowires at the Wafer Scale from an Aqueous Solution

Fahrenkrug, Eli; Gu, Junsi; Jeon, Sohee; Veneman, P. Alex; Goldman, R. S.; Maldonado, Stephen

doi:10.1021/nl404228z

Cited by 59 publications

(87 citation statements)

References 34 publications

(53 reference statements)

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“…10,13,14 In general, the data shown here further emphasize that ec-LLS can be a synthetic materials method at the micro-, meso-, and macro-length scales. However, with liquid Ga or GaIn microdroplets, the growing Ge crystal(s) push the liquid metal nano/microdroplet away from the surface because nucleation and crystal growth occur preferentially at the interface between the liquid metal droplet and the support substrate.…”

Section: D504supporting

confidence: 58%

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Electrochemical Liquid-Liquid-Solid Deposition of Ge at Hg Microdroplet Ultramicroelectrodes

Zhang¹,

Fahrenkrug²,

Maldonado³

2016

J. Electrochem. Soc.

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Individual Hg microdroplet electrodes were used to perform Ge electrochemical liquid-liquid-solid (ec-LLS) crystal growth in aqueous solutions containing dissolved GeO2. The Hg microdroplets were prepared by electrodeposition of Hg onto pre-existing Pt ultramicroelectrodes (r < 10 μm). These Hg microdroplet ultramicroelectrode platforms were then used for analyses of Ge ec-LLS by both voltammetry and amperometry. Voltammetric responses indicated that Ge was neither immediately nor quantitatively dissolved into Hg upon electroreduction of aqueous solutions of GeO2. Separately, chronoamperometry performed at large overpotentials for reduction of dissolved GeO2 yielded crystalline Ge but with notable differences as compared to ec-LLS at a bulk Hg pool electrode. One set of experiments featured the surface of the Hg microdroplets possessing a complete Ge shell. The data suggested this shell formed within the first 1000 s and essentially passivated the electrode against further heterogeneous GeO2 reduction but allowed limited H+ reduction. The other set of experiments exhibited a similar shell but with fissures or cracks that exposed fresh Hg to the electrolyte and allowed Ge electrodeposition to persist much longer. In these experiments, hollow, spiral crystalline Ge tubes were extruded from the interior of the Hg microdroplets.

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Section: D504supporting

confidence: 58%

“…13,14 There are no previous reports on whether the same is achievable with small Hg droplets, i.e. at volumes 10 10 times smaller than our previous investigation with Hg as an ec-LLS electrode/medium.…”

mentioning

confidence: 61%

Electrochemical Liquid-Liquid-Solid Deposition of Ge at Hg Microdroplet Ultramicroelectrodes

Zhang¹,

Fahrenkrug²,

Maldonado³

2016

J. Electrochem. Soc.

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“…In fact, we showed both homoepitaxy and heteroepitaxy in ec-LLS of Ge nanowires. 37 In these experiments, the liquid Ga nanodroplets were always observed on the tip of the Ge nanowire. For longer ec-LLS nanowire experiments, stacking faults were observed that caused kinking.…”

Section: Ec-lls Synthesis Of Crystalline Group IV Semiconductorsmentioning

confidence: 89%

“…For longer ec-LLS nanowire experiments, stacking faults were observed that caused kinking. 37 Notably, all of the nanowires across a given film showed kinking at essentially the same position (Figure 5c), implying that the stacking faults formed consistently and simultaneously for each nanowire. A consequence of the stacking faults was an abrupt change in growth direction within the [111] family.…”

Section: Ec-lls Synthesis Of Crystalline Group IV Semiconductorsmentioning

confidence: 91%

Electrochemical Liquid–Liquid–Solid (ec-LLS) Crystal Growth: A Low-Temperature Strategy for Covalent Semiconductor Crystal Growth

Fahrenkrug

Maldonado

2015

Acc. Chem. Res.

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This Account describes a new electrochemical synthetic strategy for direct growth of crystalline covalent group IV and III-V semiconductor materials at or near ambient temperature conditions. This strategy, which we call "electrochemical liquid-liquid-solid" (ec-LLS) crystal growth, marries the semiconductor solvation properties of liquid metal melts with the utility and simplicity of conventional electrodeposition. A low-temperature liquid metal (i.e., Hg, Ga, or alloy thereof) acts simultaneously as the source of electrons for the heterogeneous reduction of oxidized semiconductor precursors dissolved in an electrolyte as well as the solvent for dissolution of the zero-valent semiconductor. Supersaturation of the semiconductor in the liquid metal triggers eventual crystal nucleation and growth. In this way, the liquid electrolyte-liquid metal-solid crystal phase boundary strongly influences crystal growth. As a synthetic strategy, ec-LLS has several intrinsic features that are attractive for preparing covalent semiconductor crystals. First, ec-LLS does not require high temperatures, toxic precursors, or high-energy-density semiconductor reagents. This largely simplifies equipment complexity and expense. In practice, ec-LLS can be performed with only a beaker filled with electrolyte and an electrical circuit capable of supplying a defined current (e.g., a battery in series with a resistor). By this same token, ec-LLS is compatible with thermally and chemically sensitive substrates (e.g., plastics) that cannot be used as deposition substrates in conventional syntheses of covalent semiconductors. Second, ec-LLS affords control over a host of crystal shapes and sizes through simple changes in common experimental parameters. As described in detail herein, large and small semiconductor crystals can be grown both homogeneously within a liquid metal electrode and heterogeneously at the interface of a liquid metal electrode and a seed substrate, depending on the particular details chosen for ec-LLS. Third, the rate of introduction of zero-valent materials into the liquid metal is precisely gated with a high degree of resolution by the applied potential/current. The intent of this Account is to summarize the key elements of ec-LLS identified to date, first contextualizing this method with respect to other semiconductor crystal growth methods and then highlighting some unique capabilities of ec-LLS. Specifically, we detail ec-LLS as a platform to prepare Ge and Si crystals from bulk- (∼1 cm(3)), micro- (∼10(-10) cm(3)), and nano-sized (∼10(-16) cm(3)) liquid metal electrodes in common solvents at low temperature. In addition, we describe our successes in the preparation of more compositionally complex binary covalent III-V semiconductors.

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“…5,[35][36][37] More recently, an electrochemical electrolyte-liquid-solid analog has been demonstrated for growth of Ge nanowires. [38][39][40] In another approach nanowire growth of metallic nanostructures capitalizes on the intrinsic or additive engineered anisotropic energetics and/or growth kinetics on different crystal facets. 21,41 For example, adsorption of anions or dilute metal ion additives, via under potential deposition (upd), enables fabrication of structures such as Au nanospikes of moderate aspect ratio using a Pb additive 42,43 and highly faceted, moderately elongated dendrite-like grains using Tl as an additive 44 on unpatterned substrates.…”

mentioning

confidence: 99%

Morphological Transitions during Au Electrodeposition: From Porous Films to Compact Films and Nanowires

Josell

Levin

Moffat

2015

J. Electrochem. Soc.

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Gold electrodeposition was studied in a sulfite electrolyte to which micromolar concentrations of Tl 2 SO 4 were added. Hysteresis and a regime of negative differential resistance (NDR) evident in electroanalytical measurements are correlated with deposit morphology and interpreted through measurements of thallium underpotential deposition (upd). Deposit morphologies range from specular surfaces to highly faceted dendrite-like grains of moderate aspect ratio and, for potentials within the NDR region, sub-50 nm diameter, high aspect ratio 110 oriented single crystal nanowires. The nanowires exhibit an epitaxial relationship to the substrate that permits one step fabrication of surfaces densely covered with high aspect ratio nanowires having controlled orientations. The NDR and nanowires are a consequence of the non-monotonic relationship between Tl coverage and growth velocity; at low coverage Tl accelerates Au deposition while at higher coverage it inhibits deposition. Immiscibility of the Tl and Au supports on-going surface segregation during area expansion that accompanies nanowire growth leading to greater dilution of the additive coverage and more rapid growth at the nanowire tips, while the sidewalls remain passivated by a saturated Tl coverage. Interest in nanostructures is driven by the unique properties associated with high surface area to volume materials that express quantum or mesoscale phenomena of importance to diverse subjects ranging from biology and medicine 1-3 to optics and energy conversion. [4][5][6][7] Of particular interest is the substantial literature on solution or vapor processing to yield a wide variety of nanostructures including high aspect ratio nanowires. 4,8,9 Solution-based, chemical reduction processes are attractive because they are inexpensive and scalable.9-18 Subsequent processing involving particle packing and/or substrate interactions can lead to higher order organization and colloidal crystals.19 Alternatively, nanostructures can be grown on or in surfaces that have been shaped by lithography or other means to obtain control of orientation and/or placement.8 Electrochemical processing may involve throughmask plating in patterned templates 20,21 or superconformal electrodeposition of metals and alloys [22][23][24][25][26][27][28][29][30][31] including gold 32-34 in high aspect ratio features. However, these processes require nanoscale patterned topography to create such structures and the associated patterning often comes with increased processing complexity.Controlled anisotropic growth and orientation, if not position, is possible through vapor-liquid-solid (VLS) growth processes. Fabrication of semiconductor and oxide nanowires typically uses dewetting of a low melting point metal catalyst where the resulting clusters set the feature size while epitaxy to the underlying substrate can control the growth orientation. 5,[35][36][37] More recently, an electrochemical electrolyte-liquid-solid analog has been demonstrated for growth of Ge nanowires. [38][39][40] In another ap...

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Room-Temperature Epitaxial Electrodeposition of Single-Crystalline Germanium Nanowires at the Wafer Scale from an Aqueous Solution

Cited by 59 publications

References 34 publications

Electrochemical Liquid-Liquid-Solid Deposition of Ge at Hg Microdroplet Ultramicroelectrodes

Electrochemical Liquid-Liquid-Solid Deposition of Ge at Hg Microdroplet Ultramicroelectrodes

Electrochemical Liquid–Liquid–Solid (ec-LLS) Crystal Growth: A Low-Temperature Strategy for Covalent Semiconductor Crystal Growth

Morphological Transitions during Au Electrodeposition: From Porous Films to Compact Films and Nanowires

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