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Fenter, Paul; Eisenberger, P.; Liang, K. S.

doi:10.1103/physrevlett.70.2447

Cited by 430 publications

(343 citation statements)

References 15 publications

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“…Phase transitions and desorption of alkanethiol monolayers on Au(1 1 1) have been observed at elevated temperatures with STM [20,21,[24][25][26][27]. The two dimensional melting temperature of alkanethiol SAMs increases with increasing chain length of the alkane backbone [22,23,27]. The transition temperature in the junctions being independent of chain length can therefore not yet be explained.…”

Section: Introductionmentioning

confidence: 97%

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Stability of large-area molecular junctions

Akkerman

Kronemeijer

Harkema

et al. 2010

Organic Electronics

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Stability of large-area molecular junctions Akkerman, Hylke B.; Kronemeijer, Auke J.; Harkema, Jan; van Hal, Paul A.; Smits, Edsger C. P.; de Leeuw, Dago M.; Blom, Paul W. M. Take-down policy If you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim. Keywords:Molecular electronics Molecular devices Self-assembled monolayers Stability Alkanedithiols a b s t r a c tThe stability of molecular junctions is crucial for any application of molecular electronics. Degradation of molecular junctions when exposed to ambient conditions is regularly observed. In this report the stability of large-area molecular junctions under ambient conditions for more than two years is presented. Furthermore, the thermal stability of molecular junctions at elevated temperatures is investigated. A transition temperature at 50°C was observed for molecular junctions based on self-assembled monolayers of alkanedithiols, above which the resistance decreases exponentially with temperature. This transition temperature limits the process window during fabrication and the temperature window during operation.

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Section: Introductionmentioning

confidence: 97%

“…Thermal stability of SAMs on Au surfaces has been studied extensively [17][18][19][20][21][22][23]. Phase transitions and desorption of alkanethiol monolayers on Au(1 1 1) have been observed at elevated temperatures with STM [20,21,[24][25][26][27].…”

Section: Introductionmentioning

confidence: 99%

Stability of large-area molecular junctions

Akkerman

Kronemeijer

Harkema

et al. 2010

Organic Electronics

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“…The measurements also reiterate the importance of secondary structure in macromolecular activity. SAM structure and packing, which are strongly influenced by chain length (39,40), have a strong control on calcite nucleation. A recent molecular dynamics analysis suggests these effects may be related to the degree of symmetry in interactions between SAM monomers and its impact on SAM order, highlighting once again the importance of cooperativity in both SAM-crystal-binding and templatedirected nucleation (35).…”

Section: Significancementioning

confidence: 99%

Reconciling disparate views of template-directed nucleation through measurement of calcite nucleation kinetics and binding energies

Hamm

Giuffre

Han

et al. 2014

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

136

173

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The physical basis for how macromolecules regulate the onset of mineral formation in calcifying tissues is not well established. A popular conceptual model assumes the organic matrix provides a stereochemical match during cooperative organization of solute ions. In contrast, another uses simple binding assays to identify good promoters of nucleation. Here, we reconcile these two views and provide a mechanistic explanation for template-directed nucleation by correlating heterogeneous nucleation barriers with crystal-substrate-binding free energies. We first measure the kinetics of calcite nucleation onto model substrates that present different functional group chemistries (carboxyl, thiol, phosphate, and hydroxyl) and conformations (C11 and C16 chain lengths). We find rates are substrate-specific and obey predictions of classical nucleation theory at supersaturations that extend above the solubility of amorphous calcium carbonate. Analysis of the kinetic data shows the thermodynamic barrier to nucleation is reduced by minimizing the interfacial free energy of the system, γ. We then use dynamic force spectroscopy to independently measure calcitesubstrate-binding free energies, ΔG b . Moreover, we show that within the classical theory of nucleation, γ and ΔG b should be linearly related. The results bear out this prediction and demonstrate that low-energy barriers to nucleation correlate with strong crystal-substrate binding. This relationship is general to all functional group chemistries and conformations. These findings provide a physical model that reconciles the long-standing concept of templated nucleation through stereochemical matching with the conventional wisdom that good binders are good nucleators. The alternative perspectives become internally consistent when viewed through the lens of crystal-substrate binding.B iological systems are unique in their ability to organize minerals into functional materials with complex patterns and architectures. A substantial body of evidence suggests specialized macromolecules, particularly proteins (1, 2) and carbohydrates (3, 4), provide preferential sites for nucleation to direct the placement, timing, and orientation of crystals (5), both intra-and extracellular. Within the biomineralization community, the conventional view of biologically directed nucleation is that macromolecular matrices present an interfacial match to the crystal lattice that assists in forming the crystal nucleus. This cooperative view of directed nucleation is rooted in the collective action of multiple residues that guide the organization of ions into a configuration defining the energetic minimum for the system. A series of in vitro observations have reinforced this picture by showing that highly ordered organic monolayers can control the location and orientation of calcite crystals precipitated from solution (6). In this approach, good templates are revealed through a direct functional assay, i.e., nucleation. Over the years, this view of mineralization, both in the context of natural stru...

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“…[43][44][45][46][47][48][49] Substrate oxidation due to oxygen molecule penetration through the OML occurs at increasing rates with decreasing chain length, indicating increasingly poor organization or porosity of the alkyl chains layer. 12 Preferential post-grafting oxidation (Fig. 1) is expected at specific areas with either lower molecular coverage or higher molecular disorder; hence, physically adsorbed oxygen-containing species can be trapped within the organic film or bound to the pinholes.…”

mentioning

confidence: 99%

“…[7][8][9][10] The organization of linear molecules in quasi-2D assemblies is the result of a delicate interplay between substrateadsorbate interactions and lateral intermolecular (electrostatic, van der Waals) interactions. 11,12 Strong covalent grafting produces robust assemblies, however irreversible binding to the semiconductor substrate may lead to substantial fluctuations in molecular packing density and formation of domains with variable average orientation. 1,13,14 In spite of the intrinsic topological disorder of organic monolayers (OML) covalently bound to semiconductor (SC) surfaces, electrical transport properties of such M-OML-SC devices have been widely studied due to their relatively low density of electrically active defects at the OML-Si interface, at least in their as-grown state.…”

mentioning

confidence: 99%

Barrier height distribution and dipolar relaxation in metal-insulator-semiconductor junctions with molecular insulator: Ageing effects

Fadjie-Djomkam

Ababou‐Girard

Godet

2012

Journal of Applied Physics

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To cite this version:Alain-Bruno Fadjie-Djomkam, Soraya Ababou-Girard, Christian Godet. Barrier height distribution and dipolar relaxation in metal-insulator-semiconductor junctions with molecular insulator: Ageing effects. Journal of Applied Physics, American Institute of Physics, 2012, 112, pp.113701-1-113701-11 Related ArticlesAtomic layer deposition of Al2O3 on GaSb using in situ hydrogen plasma exposure Appl. Phys. Lett. 101, 231601 (2012) Defect induced mobility enhancement: Gadolinium oxide (100) on Si(100) Appl. Phys. Lett. 101, 222903 (2012) Band alignment in Ge/GeOx/HfO2/TiO2 heterojunctions as measured by hard x-ray photoelectron spectroscopy Appl. Phys. Lett. 101, 222110 (2012) Electronic properties at the oxide interface with silicon and germanium through x-ray induced oxide charging Appl. Phys. Lett. 101, 211606 (2012) A computational study of graphene silicon contact J. Appl. Phys. 112, 104502 (2012) Additional information on J. Appl. Phys. Electrical transport through molecular monolayers being very sensitive to disorder effects, admittance and current density characteristics of Hg//C 12 H 25 -n Si junctions incorporating covalently bonded n-alkyl molecular layers, were investigated at low temperature (150-300 K), in the as-grafted state and after ageing at the ambient. This comparison reveals local oxidation effects both at the submicron scale in the effective barrier height distribution and at the molecular scale in the dipolar relaxation. In the bias range dominated by thermionic emission and modified by the tunnel barrier (TB) attenuation, expðÀb 0 d T Þ, where d T is the thickness of the molecular tunnel barrier and b 0 is the inverse attenuation length at zero applied bias, some excess current is attributed to a distribution of low barrier height patches.Complementary methods are used to analyze the current density J(V, T) characteristics of metal-insulator-semiconductor tunnel diodes. Assuming a Gaussian distribution of barrier heights centered at qU B provides an analytical expression of the effective barrier height, qU EFF ðTÞ ¼ qU B þ ðkTÞb 0 d T À ðqdUÞ 2 =2kT; this allows fitting of the distribution standard deviation dU and tunnel parameter ðb 0 d T Þ over a wide temperature range. In a more realistic modeling including the voltage dependence of barrier height and circular patch area, the so-called "pinch-off" effect is described by a distribution of parameter c ¼ 3ðD P R 2 P =4Þ 1=3 , which combines interface potential modulation and patch area variations. An arbitrary distribution of c values, fitted to low-temperature J(V) data, is equally well described by Gaussian or exponential functions. Ageing in air also increases the interface oxidation of Si substrate and affects the density of localized states near mid gap, which typically rises to the high 10 11 eV À1 cm À2 range, as compared with D S < 10 11 eV À1 cm À2 in the as-grafted state. The bias-independent relaxation observed near 1 kHz at low temperature may be attributed either to dipoles in the alkyl chain in...

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Chain-length dependence of the structures and phases ofCH3(CH2<

Cited by 430 publications

References 15 publications

Stability of large-area molecular junctions

Stability of large-area molecular junctions

Reconciling disparate views of template-directed nucleation through measurement of calcite nucleation kinetics and binding energies

Barrier height distribution and dipolar relaxation in metal-insulator-semiconductor junctions with molecular insulator: Ageing effects

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