Submolecular Potential Profiling Across Organic Monolayers

Filip-Granit, † Neta; Boom, Milko E. van der; Yerushalmi, Roie; Scherz, A.; Cohen, Hagai

doi:10.1021/nl0620435

Cited by 20 publications

(20 citation statements)

References 28 publications

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“…Islam and Mukherjee have used the positive charging to derive information about the structure of Langmuir-Blodgett films of cadmium arachidate on silicon substrate [11]. A recent elegant application reported by Cohen and co-workers has extended the technique to profile the submolecular potentials developed across organic monolayers [12].…”

Section: Introductionmentioning

confidence: 99%

Methods for probing charging properties of polymeric materials using XPS

Sezen

Ertaş

Süzer

2010

Journal of Electron Spectroscopy and Related Phenomena

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a b s t r a c tVarious thin polystyrene, PS, and poly(methyl methacrylate), PMMA and PS + PMMA blend films have been examined using the technique of recording X-ray photoelectron spectrum while the sample is subjected to ±10 V d.c. bias, and three different forms of (square-wave (SQW), sinusoidal (SIN) and triangular (TRG)), a.c. pulses. All films exhibit charging shifts as observed in the position of the corresponding C1s peak under d.c. bias. The a.c. pulses convert the single C1s peak to twinned peaks in the case of the square-wave form, and distort severely in the cases of the SIN, and TRG forms, and all three of them exhibit strong frequency dependence. In order to mimic and better understand the behavior of these polymeric materials, an artificial dielectric system consisting of a clean Si-wafer coupled to an external 1 M resistor and 56 nF capacitor is created, and its response to different forms of voltage stimuli, is examined in detail. A simple electrical circuit model is also developed treating the system as consisting of a parallel resistor and a series capacitor. With the help of the model, the response of the artificial system is successfully calculated as judged by comparison with the experimental data. Using one high frequency SQW measurements, the off-set in the charging shift due to the extra low-energy neutralizing electrons is estimated. After correcting the corresponding off-set shifts, the XPS spectra of the three different PS films, one PMMA, and one PS + PMMA blend film are re-examined. As a result of these detailed analysis, there emerges a clear relationship between the thicknesses of the PS films with their charging abilities. In the blend film, PS and PMMA domains are electrically separated, and exhibit different charging shifts, however, the presence of one is felt by the other. Hence, the PS component shifts are larger in the blend, due to the presence of PMMA domains, which has intrinsically a larger R eff , and conversely the PMMA component shifts are smaller due to the presence of PS domains.

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Section: Introductionmentioning

confidence: 99%

Methods for probing charging properties of polymeric materials using XPS

Sezen

Ertaş

Süzer

2010

Journal of Electron Spectroscopy and Related Phenomena

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“…It is nondestructive, relatively quick and easy for operation, and can, in principle, achieve excellent depth resolution in dielectric systems consisting of sufficient chemical contrast, down to the atomic scale. 22 The accuracy in line-shift determination is typically around 20-50 meV, frequently even Ͻ10 meV, which corresponds here to depth resolution on the order of 1-2 Å. On the other hand, as indeed observed in the O and Si ox signals, potential gradients across layers of finite thicknesses impose line shape distortions which can, in general, be quite large.…”

mentioning

confidence: 57%

“…20,21 CREM and CSC are both noncontact methods, proposing unique capabilities, down to atomic scale resolution of the electrostatic potential. 22 In the present work, we exploit the CSC capabilities for characterizing the internal structure of SiON layers, where the chemical contrast across the layer is rather poor. Line shape analysis is applied for continuous intermixing distribution functions, and comparison with alternative techniques is presented.…”

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confidence: 99%

Electrical depth profiling in thin SiON layers

Rozenblat

Rosenwaks

Segev

et al. 2009

Applied Physics Letters

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Electrical conduction mechanism in silicon nitride and oxy-nitride-sputtered thin filmsThe internal structure of SiON films is extracted electrically, demonstrating an efficient, noncontact, nondestructive means for depth compositional analysis in gate oxides. The electrical data, obtained using x-ray photoelectron spectroscopy ͑XPS͒ based controlled surface charging ͑CSC͒, are compared with independent time of flight secondary ion mass spectroscopy and angle resolved XPS data. Inhomogeneous composition with significant nitrogen enrichment at the top of the oxide layer is observed. Capabilities of the CSC method in treating heterostructures of poor chemical contrast are discussed.

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“…The integrated densities and the potential energy differences extracted are of the order of a few hundred millivolts, in good correspondence with experiment. 27,28 In the context of chemically resolved experiments, the correlation between the extracted potential change and the underlying charge density will assist in inverting the observable potential change into molecular properties. More generally, the approach could benefit the interpretation of various experiments that probe electron transmission via molecular layers.…”

Section: Discussionmentioning

confidence: 99%

“…The numerical simulations presented in the present paper aim primarily to explore the type and quality of information that can be extracted from the class of emerging noncontact transport measurements 21,[26][27][28]45,46 by giving both timedependent pictures of the electron flow through molecular layers and the static observables of the experiment. The latter are the relative charge density between atomic sites and the potential differences at the atomic sites in the absence and the presence of the injected electron.…”

Section: Introductionmentioning

confidence: 99%

The information content of electron flow through adsorbed molecular monolayers

Sherratt¹,

Cohen

Seideman³

2009

The Journal of Chemical Physics

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We point to the ability of noncontact measurements of electron transport via self-assembled monolayers to provide chemical, A-resolved information about the underlying molecule. A conceptual framework is presented to model a current flow of soft electrons through a molecular monolayer to a substrate and explore the information content of this and other emerging noncontact measurements. A numerical scheme is developed where advantage is taken of the split-operator formalism to propagate the incident electronic wave function over a suitable periodic potential energy surface representing the self-assembled monolayer. The (experimentally observable) potential difference introduced by the transmitted electrons is extracted from the time-averaged electron density using the Poisson equation of classical electrostatics.

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Submolecular Potential Profiling Across Organic Monolayers

Abstract: Potential profiles across molecular layers are constructed by means of noncontact electrically stimulated photoelectron spectroscopy, probing for the first time the molecule-substrate interface potential and resolving local screening effects across inner phenyl groups.

Cited by 20 publications

References 28 publications

Methods for probing charging properties of polymeric materials using XPS

Methods for probing charging properties of polymeric materials using XPS

Electrical depth profiling in thin SiON layers

The information content of electron flow through adsorbed molecular monolayers

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