Growth modes of epitaxial copper films on c-sapphire

Knoll, E.; Bialas, H.

doi:10.1016/0040-6090(94)90162-7

Cited by 9 publications

(8 citation statements)

References 11 publications

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“…There are six diffraction spots in the pole figure instead of three because there are two discrete sets of crystallites from twinning with an azimuthal angle of 60°a part. Twinning defects are common in the epitaxial growth of fcc metals due to both growth accidents and grain encounters (16,17). Similar to the Cu(200) pole figure for Cu(111) growth on Ti/Al 2 O 3 (0001), the Cu(111) pole figure for Cu(100) growth on Si(100) shows discrete Bragg reflections, indicating cube-oncube epitaxial growth of Cu on the Si(100) substrate (Fig.…”

Section: Resultsmentioning

confidence: 64%

“…In particular, researchers have used physical vapor deposition (PVD) and molecular beam epitaxy to successfully grow Cu epitaxially on Si and Al 2 O 3 (12,13,(15)(16)(17). It is worth noting that Si has garnered interest as a cathode in photoelectrochemical (PEC) cells (18,19), and developing synthetic methods to engineer the surface structure of Cu on Si could be advantageous for controlling the performance and selectivity of PEC CO 2 R devices.…”

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confidence: 99%

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Engineering Cu surfaces for the electrocatalytic conversion of CO ₂ : Controlling selectivity toward oxygenates and hydrocarbons

Hahn

Hatsukade

Kim

et al. 2017

Proc. Natl. Acad. Sci. U.S.A.

369

329

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In this study we control the surface structure of Cu thin-film catalysts to probe the relationship between active sites and catalytic activity for the electroreduction of CO 2 to fuels and chemicals. Here, we report physical vapor deposition of Cu thin films on large-format (∼6 cm 2 ) single-crystal substrates, and confirm epitaxial growth in the <100>, <111>, and <751> orientations using X-ray pole figures. To understand the relationship between the bulk and surface structures, in situ electrochemical scanning tunneling microscopy was conducted on Cu(100), (111), and (751) thin films. The studies revealed that Cu(100) and (111) have surface adlattices that are identical to the bulk structure, and that Cu(751) has a heterogeneous kinked surface with (110) terraces that is closely related to the bulk structure. Electrochemical CO 2 reduction testing showed that whereas both Cu(100) and (751) thin films are more active and selective for C-C coupling than Cu(111), Cu(751) is the most selective for >2e− oxygenate formation at low overpotentials. Our results demonstrate that epitaxy can be used to grow singlecrystal analogous materials as large-format electrodes that provide insights on controlling electrocatalytic activity and selectivity for this reaction.carbon dioxide reduction | epitaxy | electrocatalysis | copper T he electrochemical reduction of CO 2 (CO 2 R) is a process that could couple to renewable energy from wind and solar to directly produce fuels and chemicals in a sustainable manner. However, developing catalysts is a major challenge for this reaction, and significant advances are needed to overcome the issues of poor energy efficiency and product selectivity. One reason for these issues is that there are a limited number of catalysts that can effectively convert CO 2 to products that require more than two electrons (>2e − products), e.g., methane, methanol, ethylene, etc. (1, 2). Therefore, developing catalysts that are effective for CO 2 R to >2e − products would greatly improve prospects for utilization, and such an endeavor requires a deeper understanding of the relevant surface chemistry.Out of the polycrystalline metals, Cu is the only one that has shown a propensity for CO 2 R to >2e − products at considerable rates and selectivity (2, 3). To date, its uniqueness is reflected by how nearly all work on catalysts with improved activity and selectivity for >2e − products is based on Cu (4-6). However, polycrystalline Cu is not particularly selective toward any one >2e − reduction product (7). Thus, it is critical to understand what active site motifs lead to this unique selectivity for further reduced products and to apply this knowledge to develop new materials with this electrocatalytic behavior.Single-crystal studies on Cu have shown that CO 2 R activity and selectivity are extremely sensitive to surface structure. In particular, facet sensitivities for C-C coupling are the most widely studied, with experimental reports concluding that Cu(100) terraces and any orientation of step sites are more...

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Section: Resultsmentioning

confidence: 64%

mentioning

confidence: 99%

Engineering Cu surfaces for the electrocatalytic conversion of CO ₂ : Controlling selectivity toward oxygenates and hydrocarbons

Hahn

Hatsukade

Kim

et al. 2017

Proc. Natl. Acad. Sci. U.S.A.

369

329

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“…The study of the Al 2 O 3 (0001)/Cu(111) epitaxy is thus of great importance and was first studied in 1968 by Katz et al and thereafter by various other research groups. ,,− The two different thermodynamically stable orientation relationships, OR-I and OR-II, between Cu(111) and c-plane sapphire are rotated by 30° about ⟨111⟩. In OR-I, Cu atoms are filling the sapphire octahedral interstitial sites with a lattice mismatch of −6.9%.…”

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confidence: 99%

Epitaxial Al₂O₃(0001)/Cu(111) Template Development for CVD Graphene Growth

et al. 2015

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Chemical vapor deposition (CVD) is widely considered to be the most economically viable method to produce graphene for high-end applications. However, this deposition technique typically yields undesired grain boundaries in the graphene crystals, which drastically increases the sheet resistance of the layer. These grain boundaries are mostly caused by the polycrystalline nature of the catalytic template that is commonly used. Therefore, to prevent the presence of grain boundaries in graphene crystals, it is crucial to develop a large scale, single-crystalline template. In this paper, we demonstrate the deposition of a single-crystalline Cu(111) film on top of a 2″ sapphire wafer. The crystalline quality of the Cu(111) templates is optimized by controlled modification of the sapphire surface termination and by tuning the Cu deposition conditions. Moreover, we find that the Cu layer transforms into an untwinned single-crystalline Cu(111) structure after annealing at typical graphene growth temperatures. This allows for the growth of high-quality graphene by the CVD technique. The findings presented in this paper are an important step forward in the production of wafer scale, single-crystalline graphene.

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“…This is not unlikely since extensive twinning in the copper grains was found in the TEM studies. Another explanation given by Knoll and Bialas [15] is that the off-centre peaks emerge from steps (different crystal planes) in the a-Al 2 O 3 (0 0 1) surface.…”

Section: Resultsmentioning

confidence: 95%

Epitaxy of copper on α-Al2O3(001) by atomic layer deposition

Törndahl

Ottosson

Carlsson

2005

Journal of Crystal Growth

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Growth modes of epitaxial copper films on c-sapphire

Cited by 9 publications

References 11 publications

Engineering Cu surfaces for the electrocatalytic conversion of CO ₂ : Controlling selectivity toward oxygenates and hydrocarbons

Engineering Cu surfaces for the electrocatalytic conversion of CO ₂ : Controlling selectivity toward oxygenates and hydrocarbons

Epitaxial Al₂O₃(0001)/Cu(111) Template Development for CVD Graphene Growth

Epitaxy of copper on α-Al2O3(001) by atomic layer deposition

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Growth modes of epitaxial copper films on c-sapphire

Cited by 9 publications

References 11 publications

Engineering Cu surfaces for the electrocatalytic conversion of CO 2 : Controlling selectivity toward oxygenates and hydrocarbons

Engineering Cu surfaces for the electrocatalytic conversion of CO 2 : Controlling selectivity toward oxygenates and hydrocarbons

Epitaxial Al2O3(0001)/Cu(111) Template Development for CVD Graphene Growth

Epitaxy of copper on α-Al2O3(001) by atomic layer deposition

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Product

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Engineering Cu surfaces for the electrocatalytic conversion of CO ₂ : Controlling selectivity toward oxygenates and hydrocarbons

Engineering Cu surfaces for the electrocatalytic conversion of CO ₂ : Controlling selectivity toward oxygenates and hydrocarbons

Epitaxial Al₂O₃(0001)/Cu(111) Template Development for CVD Graphene Growth