Crystal growth and phase selectivity of organic superconductors [.beta.-(ET)2I3 (Tc = 1.5 K) and .kappa.-(ET)2Cu(NCS)2 (Tc = 10.4 K)] on graphite electrodes

Wang, Hau H.; Montgomery, L. K.; Husting, Chad A.; Vogt, Bradley A.; Williams, Jack M.; Budz, Sandra M.; Lowry, Michael J.; Carlson, K. Douglas; Kwok, W. K.; Mikheyev, Vladimir

doi:10.1021/cm00005a004

Cited by 7 publications

(5 citation statements)

References 0 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Previous studies of the electrocrystallization of (ET) 2 I 3 salts have demonstrated that the choice of electrocrystallization conditions influences the selectivity toward the α and β polymorphs, with the kinetically favored α-phase forming at high overpotentials and the thermodynamically favored β-phase forming at low overpotentials . Furthermore, electrocrystallization on electrochemically etched HOPG favors formation of the α-phase, whereas the β-phase forms on pristine HOPG surfaces . Electrochemical parameters also influence polymorph selectivity during growth of the ET x (ReO 4 ) y salts.…”

Section: Resultsmentioning

confidence: 99%

Epitaxially Driven Assembly of Crystalline Molecular Films on Ordered Substrates

et al. 1998

View full text Add to dashboard Cite

Crystalline, molecularly thick organic films mimicking layer motifs observed in bulk crystals of conducting (ET)2X charge-transfer salts (ET = bis(ethylenedithiolo)tetrathiafulvalene, X = I3, ReO4) form on highly oriented pyrolytic graphite (HOPG) electrodes upon electrochemical oxidation of ET in electrolytes containing I3 - or ReO4 - anions. The assembly of these molecular overlayers can be observed directly by in situ atomic force microscopy (AFM), and their structures can be deduced from lattice images obtained by AFM under growth conditions. AFM data reveal two different (ET)2I3 overlayers that are distinguished by the orientation of the ET molecules. One of these overlayers (type I) exhibits lattice structure and thickness corresponding to the (001) layer of bulk β-(ET)2I3, while the other (type II) exhibits structural characteristics consistent with a slightly reconstructed version of the (1̄10) layer in crystalline β-(ET)2I3. In contrast, (ET)2ReO4 overlayers exhibit only the type II orientation, which resembles the (011) layer of bulk (ET)2ReO4. Comparison of the overlayer azimuthal orientation with respect to the underlying HOPG substrate, determined directly by AFM, reveals that each overlayer forms by coincident epitaxy in which strict commensurism is achieved only at the vertexes of a supercell comprising an array of primitive unit cells. The observed azimuthal orientations are in agreement with values predicted by either potential energy calculations or an analytical model of the overlayer−substrate interface. Strong two-dimensional intralayer interactions in the type I (001) β-(ET)2I3 overlayer and a coincident lattice match favor the formation of a crystalline layer in which the structure mimicks the bulk layer structure. However, the type II overlayers are oriented such that only one strong intralayer bonding vector remains, facilitating slight reconstructions from the bulk layer structures so that coincidence can be achieved. Calculations of overlayer−substrate and overlayer energies and elastic constants indicate that although coincident epitaxy between the (001) (ET)2ReO4 overlayer and HOPG is possible, the accumulation of interfacial stresses from noncommensurate overlayer sites within its large supercell prevents its formation. These observations, when combined with analysis of the intralayer and overlayer−substrate elastic constants, indicate that the overlayer structure and its orientation with respect to the substrate are governed by the epitaxial relationship between the substrate and large ordered arrays of molecules, reflecting a delicate balance of intralayer and overlayer−substrate energetics. The design strategy based on bulk crystallographic layers and the overlayer−substrate epitaxy represents a “crystal engineering” approach to the fabrication of molecular thin films.

show abstract

Section: Resultsmentioning

confidence: 99%

Epitaxially Driven Assembly of Crystalline Molecular Films on Ordered Substrates

et al. 1998

View full text Add to dashboard Cite

show abstract

“…It has also been shown that the presynthesis treatments of the electrode, such as polishing with fine sand paper and electrolysis in 1 M H 2 SO 4 solution, can lead to different crystalline phases (polymorphism). 26 The choice of the electrolysis solvent is limited by its ability to dissolve both the organic donor and the electrolyte. 21 For this purpose, a mixture of two or more solvents may be required, but one must keep in mind that ultimately the salt of the electro-oxidized species must not be soluble if it is to crystallize.…”

Section: Electrocrystallization: the Experimentsmentioning

confidence: 99%

“…A platinum wire is used as the working electrode. It has also been shown that the presynthesis treatments of the electrode, such as polishing with fine sand paper and electrolysis in 1 M H 2 SO 4 solution, can lead to different crystalline phases (polymorphism) . The choice of the electrolysis solvent is limited by its ability to dissolve both the organic donor and the electrolyte .…”

Section: Electrocrystallization: the Experimentsmentioning

confidence: 99%

Electrocrystallization, an Invaluable Tool for the Construction of Ordered, Electroactive Molecular Solids

et al. 1998

View full text Add to dashboard Cite

For the past three decades, the electrocrystallization technique has been used extensively to assemble a large variety of molecular ions into long range ordered single crystals of high purity. This effort is reviewed in the present paper from the initial vigorous impetus triggered by the development of organic (molecular) metals and superconductors to the continuous diverse developments toward insulating antiferromagnetic systems, the synthesis of crystals of coordination polymers, the construction of ternary and quaternary phases, the variation of molecular conformation, the use of polyfunctionalized π-donor molecules with hydrogen-bond-donor and/or -acceptor capabilities and the development of molecular alloys, with the aim of exemplifying an approach to the solid-state chemistry of molecular ions.

show abstract

“…Our laboratory recently reported the electrochemical synthesis, on HOPG electrode substrates, of crystalline monolayers based on the charge-transfer salt bis(ethylenedithiolo)tetrathiafulvalene triiodide, (ET) 2 I 3 . , Real-time in situ atomic force microscopy (AFM) revealed that because of epitaxial interactions between the monolayers and the HOPG substrate, monolayer growth initiated by electrochemical oxidation of ET in the presence of triiodide occurred exclusively on pristine terraces instead of at step edges that decorated the HOPG surface. Two monolayer structure types with the same composition were observed, one mimicking the (001) plane of β-(ET) 2 I 3 (Type I) and the other resembling a slightly expanded form of the (1̄10) plane of β-(ET) 2 I 3 (Type II).…”

Section: Introductionmentioning

confidence: 99%

Nanoconfined Electrochemical Nucleation of Crystalline Molecular Monolayers on Graphite Substrates

1998

View full text Add to dashboard Cite

Real-time in situ atomic force microscopy (AFM) has been employed to examine the electrochemical nucleation of epitaxially oriented, crystalline monolayers of bis(ethylenedithiolo)tetrathiafulvalene triiodide, (ET)2I3, on the basal plane of highly oriented pyrolytic graphite electrodes decorated with circular, single-layer-deep pits created by thermal etching. The nucleation of the monolayers in the pits is inhibited compared to the contiguous terraces. The time required for pit filling scales inversely with pit diameter, with nucleation completely suppressed in pits with diameters less than 100 nm. The suppression of growth in the pits can be attributed to the surface discontinuity created by the pit edge that prevents surface diffusion of ET growth units from the surrounding terrace to the pit. Consequently, growth of nuclei in the pits is limited by the amount of ET arriving in the pit by diffusion directly from solution. Numerical simulations of aggregate growth in pits illustrate the influences of transport and the finite boundary created by pit wall on the evolution of aggregate shape and size during growth, while revealing the most probable locations for nucleation within the pit. These studies illustrate the convenience of investigating nucleation processes triggered by electrochemically driven changes in redox state, the advantage of AFM for probing nucleation in the nanoscale-confined environments, and the role of transport in nucleation of ordered films.

show abstract

Crystal growth and phase selectivity of organic superconductors [.beta.-(ET)2I3 (Tc = 1.5 K) and .kappa.-(ET)2Cu(NCS)2 (Tc = 10.4 K)] on graphite electrodes

Cited by 7 publications

References 0 publications

Epitaxially Driven Assembly of Crystalline Molecular Films on Ordered Substrates

Epitaxially Driven Assembly of Crystalline Molecular Films on Ordered Substrates

Electrocrystallization, an Invaluable Tool for the Construction of Ordered, Electroactive Molecular Solids

Nanoconfined Electrochemical Nucleation of Crystalline Molecular Monolayers on Graphite Substrates

Contact Info

Product

Resources

About