Alkanethiol self-assembled monolayers as the dielectric of capacitors with nanoscale thickness

Rampi, Maria Anita; Schueller, Olivier; Whitesides, George M.

doi:10.1063/1.121183

Cited by 282 publications

(310 citation statements)

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“…There are mainly two approaches for wiring molecules between electrodes. One method is to make top-contact junctions, which includes scanning probe microscopy (scanning tunneling microscopy (STM) and conducting atomic force microscopy (AFM)), [11][12][13][14][15][16][17][18][19][20][21][22] cross wire junctions, [23][24][25] mercury drop electrodes [26,27] and thermally deposited metal films. [6] All devices manufactured by this kind of method can be categorized as 'prototype devices', which are very useful for fundamental investigations and have already provided many important results.…”

Section: Introductionmentioning

confidence: 99%

“…[6] All devices manufactured by this kind of method can be categorized as 'prototype devices', which are very useful for fundamental investigations and have already provided many important results. [4][5][6][7][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26][27] However, these devices are far from practical applications, as we can not imagine a nanometer device carrying a huge scanning probe microscopy (SPM) system or other systems. The other way utilizes nanogap electrodes [28][29][30][31][32] to form metal/molecule/metal devices.…”

Section: Introductionmentioning

confidence: 99%

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Nanogap Electrodes

2009

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Nanogap electrodes (namely, a pair of electrodes with a nanometer gap) are fundamental building blocks for the fabrication of nanometer‐sized devices and circuits. They are also important tools for the examination of material properties at the nanometer scale, even at the molecular scale. In this review, the techniques for the fabrication of nanogap electrodes, the preparation of assembled devices based on the nanogap electrodes, and the potential application of these nanodevices for analysis of material properties are introduced. The history, the research status, and the prospects of nanogap electrodes are also discussed.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Nanogap Electrodes

2009

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“…Comparing these data with data taken by a single user (Figure 7), we observe β odd = 1.19 ± 0.08 and β even = 1.05 ± 0.06 n C -1 at -0.5 V. Our value of β for the even n-alkanethiols occupies the high end of the range of values reported for systems using Hg-SAM electrodes and spin-cast polymer electrodes (β even = 0.71 -1.1 n C -1 ). 66,67,78,[144][145][146][147] Likewise, the separate fits to Equation 1 of data from odd-and even-numbered alkanethiols give two log-normally distributed estimates for the pre-exponential factor: Reproducibility. There are two axes along which to assess the reproducibility of measurements using Ag TS -SC n //Ga 2 O 3 /EGaIn junctions: dependence on the technique of the operator, and dependence on the ambient conditions of measurement.…”

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confidence: 99%

Odd−Even Effects in Charge Transport across Self-Assembled Monolayers

et al. 2011

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This paper compares charge transport across self-assembled monolayers (SAMs) of nalkanethiol containing odd and even numbers of methylenes. Ultraflat template-stripped silver (Ag TS ) surfaces supported the SAMs, while top-electrodes of eutectic galliumindium (EGaIn) contacted the SAMs to form metal/SAM//oxide/EGaIn junctions. TheEGaIn spontaneously reacts with ambient oxygen to form a thin (~ 2 nm) oxide layer.This oxide layer enabled EGaIn to maintain a stable, conical shape (convenient for forming microcontacts to SAMs) while retaining the ability to deform and flow upon contacting a hard surface. Conical electrodes of EGaIn conform (at least partially) to 2 SAMs, and generate high yields of working junctions. Ga 2 O 3 /EGaIn top electrodes enable the collection of statistically significant numbers of data in convenient periods of time. The observed difference in charge transport between n-alkanethiols with odd-and even-numbers of methylenes -the "odd-even effect" -is statistically discernable using these junctions, and demonstrates that this technique is sensitive to small differences in the structure and properties of the SAM. Alkanethiols with an even number of methylenes exhibit the expected exponential decrease in current density (J) with increasing chain length, as do alkanethiols with an odd number of methylenes. This trend disappears, however, when the two datasets are analyzed together; alkanethiols with an even number of methylenes typically show higher J than homologous alkanethiols with an odd number of methylenes. The precision of the present measurements, and the statistical power of the present analysis, were only sufficient to identify, with statistical confidence, the difference between an odd and even number of methylenes with respect to J, but not with respect to the tunneling decay constant, β, or the pre-exponential factor, J 0 .3

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“…1 In addition to the standard electrical measurements, STM, AFM, and Kelvin probe techniques are widely used to elucidate the structural changes accompanying these processes. [2][3][4][5][6] When chemical information is also needed, XPS is usually the preferred spectroscopic technique because all elements, except for hydrogen, and their oxidation state(s) can easily be identified. 7 One of the disadvantages of the XPS technique is that additional positive charges are naturally introduced as a consequence of the photoemission process.…”

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Time-Resolved XPS Analysis of the SiO₂/Si System in the Millisecond Range

2004

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By applying voltage pulses to the sample rod while recording the spectrum, we show, for the first time, that it is possible to obtain a time-resolved XPS spectrum in the millisecond range. The Si 2p spectrum of a silicon sample containing a ca. 400-nm oxide layer displays a time-dependent charging shift of ca. 1.7 eV with respect to the Au 4f peaks of a gold metal strip in contact with the sample. When gold is deposited as C 12 -thiol-capped nanoclusters onto the same sample, this time the Au 4f peaks also display time-dependent charging behavior that is slightly different from that of the Si 2p peak. This charging/discharging is related to emptying/filling of the hole traps in the oxide layer by the stray electrons within the vacuum system guided by the external voltage pulses applied to the sample rod, which can be used to extract important parameter(s) related to the dielectric properties of surface structures.Charging/discharging is one of the fundamental processes dictating both the thermodynamics and the kinetics of the various physicochemical changes taking place on surfaces. 1 In addition to the standard electrical measurements, STM, AFM, and Kelvin probe techniques are widely used to elucidate the structural changes accompanying these processes. [2][3][4][5][6] When chemical information is also needed, XPS is usually the preferred spectroscopic technique because all elements, except for hydrogen, and their oxidation state(s) can easily be identified. 7 One of the disadvantages of the XPS technique is that additional positive charges are naturally introduced as a consequence of the photoemission process. These charges do not interfere with measurements when the surfaces are electrically conducting but can cause significant binding-energy shifts for poorly conducting samples. [8][9][10][11] Such charges are usually compensated by flooding the sample with low-energy electrons (or sometimes ions) and trying to bring the surfaces to a steady state in terms of electrons going in and out, but the complete elimination of charging is only an ideal. Surfaces can also be negatively charged if more electrons are introduced. This modification, dubbed controlled surface charging (CSC), has been successfully applied to depth profiling in the 1-10 nm range and/or to the lateral differentiation of mesoscopic layers. [12][13][14][15][16] However, prolonged exposure of the surfaces to intense low-energy electrons can cause physical and chemical damage. 9 It was even reported that the surface potential that developed from the added charging caused deintercalation in layered compounds. 17 Lau and co-workers have also utilized the CSC to extract structural and electrical properties of ultrathin dielectrics on semiconductors. [18][19][20][21][22] In a complementary study, we have recently reported that the positive charging developed on the SiO 2 /Si system can also be controlled simply by the application of an external bias to the sample rod to affect the measured binding-energy difference between the Si 4+ overlayer and the...

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Alkanethiol self-assembled monolayers as the dielectric of capacitors with nanoscale thickness

Cited by 282 publications

References 23 publications

Nanogap Electrodes

Nanogap Electrodes

Odd−Even Effects in Charge Transport across Self-Assembled Monolayers

Time-Resolved XPS Analysis of the SiO₂/Si System in the Millisecond Range

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Alkanethiol self-assembled monolayers as the dielectric of capacitors with nanoscale thickness

Cited by 282 publications

References 23 publications

Nanogap Electrodes

Nanogap Electrodes

Odd−Even Effects in Charge Transport across Self-Assembled Monolayers

Time-Resolved XPS Analysis of the SiO2/Si System in the Millisecond Range

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Product

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Time-Resolved XPS Analysis of the SiO₂/Si System in the Millisecond Range