Electrochemical studies of self-assembled monolayers using impedance spectroscopy

Einati, Hila; Mottel, Alexander; Inberg, Alexandra; Shacham‐Diamand, Yosi

doi:10.1016/j.electacta.2009.02.090

Cited by 41 publications

(27 citation statements)

References 26 publications

(32 reference statements)

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“…54 The simulation parameters are ΔV G = 97 mV (evaluated from the ConCap curve in Figure 4b), n = 20; the double-layer capacitance C d was taken to be 20 μF/ cm 2 . 55 The density of hybridized dsDNA molecules calculated using eq 1 and the measured hybridization signal of 34 mV (see Figure 4b) was 2.1 × 10 11 dsDNA/cm 2 . Thus, the hybridization efficiency amounts to be approximately 35%.…”

Section: Resultsmentioning

confidence: 99%

DNA Immobilization and Hybridization Detection by the Intrinsic Molecular Charge Using Capacitive Field-Effect Sensors Modified with a Charged Weak Polyelectrolyte Layer

Bronder

Poghossian

Scheja

et al. 2015

ACS Appl. Mater. Interfaces

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Miniaturized setup, compatibility with advanced micro- and nanotechnologies, and ability to detect biomolecules by their intrinsic molecular charge favor the semiconductor field-effect platform as one of the most attractive approaches for the development of label-free DNA chips. In this work, a capacitive field-effect EIS (electrolyte-insulator-semiconductor) sensor covered with a layer-by-layer prepared, positively charged weak polyelectrolyte layer of PAH (poly(allylamine hydrochloride)) was used for the label-free electrical detection of DNA (deoxyribonucleic acid) immobilization and hybridization. The negatively charged probe single-stranded DNA (ssDNA) molecules were electrostatically adsorbed onto the positively charged PAH layer, resulting in a preferentially flat orientation of the ssDNA molecules within the Debye length, thus yielding a reduced charge-screening effect and a higher sensor signal. Each sensor-surface modification step (PAH adsorption, probe ssDNA immobilization, hybridization with complementary target DNA (cDNA), reducing an unspecific adsorption by a blocking agent, incubation with noncomplementary DNA (ncDNA) solution) was monitored by means of capacitance-voltage and constant-capacitance measurements. In addition, the surface morphology of the PAH layer was studied by atomic force microscopy and contact-angle measurements. High hybridization signals of 34 and 43 mV were recorded in low-ionic strength solutions of 10 and 1 mM, respectively. In contrast, a small signal of 4 mV was recorded in the case of unspecific adsorption of fully mismatched ncDNA. The density of probe ssDNA and dsDNA molecules as well as the hybridization efficiency was estimated using the experimentally measured DNA immobilization and hybridization signals and a simplified double-layer capacitor model. The results of field-effect experiments were supported by fluorescence measurements, verifying the DNA-immobilization and hybridization event.

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Section: Resultsmentioning

confidence: 99%

DNA Immobilization and Hybridization Detection by the Intrinsic Molecular Charge Using Capacitive Field-Effect Sensors Modified with a Charged Weak Polyelectrolyte Layer

Bronder

Poghossian

Scheja

et al. 2015

ACS Appl. Mater. Interfaces

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“…14,32 In the case of Octyl(H) (Figure 4), H_100 shows the highest charge transfer resistance, measured from the semicircle diameter, which is indicative of a low ionic permeability of the electrolyte in the organic structure. The R ct values strongly decrease for H_80 and H_150, indicating a more disordered and nonuniform layer, where the electrolyte can permeate.…”

Section: ■ Experimental Sectionmentioning

confidence: 99%

Alkylsilane–SiO₂ Hybrids. A Concerted Picture of Temperature Effects in Vapor Phase Functionalization

et al. 2015

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The vapor-phase deposition of triethoxy(octyl)-silane and 1H,1H,2H,2H-perfluoroctyltriethoxysilane on silica substrates was studied at different temperatures (70−150°C). An original combination of spectroscopic ( 13 C and 29 Si solid state NMR, FTIR), electrochemical (CV, EIS), and surface (surface free energy determinations, AFM) characterization techniques was adopted to shed light on the role played by the alkylsilane structure and deposition temperature on the resulting layer. As for the unfluorinated molecule, both wettability and ion permeability displayed a bell-shaped curve with respect to the functionalization temperature. Spectroscopic techniques showed similar trends in the functionalization degree and suggested the formation of oligomers/polymers covalently attached to the surface. 29 Si NMR proved that higher functionalization temperatures increase lateral polymerization across the alkylsilane layer. Conversely, the wettability was almost invariant with the functionalization temperature for the fluorinated analogue. However, electrochemical and spectroscopic results had a significant dependence on the functionalization conditions, even more marked than for the unfluorinated alkylsilane. The higher thermal reactivity of fluorinated molecules led to vertical polymerization, as supported by very high water contact angles, diffusion components in EIS, and a lower degree of covalent bonding with the surface. Optimal deposition conditions were identified at 100 and 90°C for the unfluorinated and fluorinated alkylsilane, respectively.

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“…This equivalent circuit consists of several impedance elements in series: the model slurry resistance ͑R s ͒, the capacitive loop for the solidelectrolyte interface ͑R 1 ,C 1 ͒, and the capacitive loop for the passive film ͑R 2 ,C 2 ͒. 9 However, the capacitances have been replaced with constant phase elements ͑CPEs͒ in Fig. 4 to phenomenologically represent the effect of surface heterogeneity.…”

Section: Resultsmentioning

confidence: 99%

Poly(ethyleneimine) as a Passivating Agent for Ta Chemical Mechanical Planarization

Sharma

Suni

Brands

et al. 2010

Electrochem. Solid-State Lett.

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We report poly͑ethyleneimine͒ ͑PEI͒ as a possible passivating agent for Ta during chemical mechanical planarization ͑CMP͒. Studies by electrochemical impedance spectroscopy in a model CMP slurry suggest that PEI forms a polymer film atop a Ta electrode, and voltammetry studies of Ta in 2.5 M HF suggest that PEI films suppress the formation of Ta oxide. Because Ta oxide is mechanically hard, suppressing Ta oxide growth may allow reduced downforce or higher removal rates. These observations are consistent with an increase of approximately 3 times in the Ta removal rate in a model CMP slurry upon addition of 3000 ppm PEI.When Cu replaced Al and W as the interconnect/via material in Si-based semiconductor devices in the late 1990s, Ta and TaN diffusion barriers were introduced between the interconnect wiring and the active device region because Cu forms a deep level defect in Si. 1,2 At that time, chemical mechanical planarization ͑CMP͒ was introduced for both Cu and Ta removal and nanoscale planarization. 3,4 Cu is easily chemically etched, so the chemical component of Cu CMP is quite substantial. Cu CMP slurries typically contain benzotriazole, which forms a passive film of the order 10 nm thick that inhibits formation of thicker Cu oxide films. 5 The formation of thick metal oxide films is widely considered to be undesirable as they likely require significant force to abrade. 6 Ta is a much more active metal than Cu, so suppressing Ta oxidation is more difficult. In addition, both Ta and the Ta native oxide ͑Ta 2 O 5 ͒ are mechanically harder than Cu and its oxide. For this reason, Ta CMP is predominantly mechanical, requiring higher downforce and/or higher abrasive concentrations than Cu CMP. The Ta native oxide can only be chemically removed in aqueous HF, 7 and Ta CMP slurries containing F ions have been developed. 8 However, polymer CMP additives that restrict the growth of Ta oxide following mechanical abrasion would be desirable. Here, poly͑eth-yleneimine͒ ͑PEI͒ is studied as a possible additive to Ta CMP slurries, with the goal being to suppress the formation of Ta oxide. PEI enhances the rate of Ta CMP, and in situ studies by electrochemical impedance spectroscopy ͑EIS͒ demonstrate that PEI forms an adherent film on Ta. It is believed that this is the first report of polymer film formation atop Ta that increases the removal rate during Ta CMP. ExperimentalDeagglomerated ␥-alumina particles ͑50 nm diameter͒ were obtained from Buehler, whereas PEI ͑Mw 70,000 g/mol͒ was obtained from Alfa Aesar. Semiconductor grade HF ͑J.T.Baker͒ was used for all electrochemistry experiments. KClO 4 was obtained from J.T.Baker. The pH was adjusted using either potassium hydroxide ͑KOH͒ or nitric acid ͑HNO 3 ͒.All electrochemistry measurements were performed with a threeelectrode setup including a Ta rotating disk electrode ͑RDE͒, a Pt spiral counter electrode, and a saturated calomel reference electrode ͑SCE͒ controlled with an EG&G PAR model 273A potentiostat/ galvanostat. EIS was studied by coupling this potentiostat to a S...

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Electrochemical studies of self-assembled monolayers using impedance spectroscopy

Cited by 41 publications

References 26 publications

DNA Immobilization and Hybridization Detection by the Intrinsic Molecular Charge Using Capacitive Field-Effect Sensors Modified with a Charged Weak Polyelectrolyte Layer

DNA Immobilization and Hybridization Detection by the Intrinsic Molecular Charge Using Capacitive Field-Effect Sensors Modified with a Charged Weak Polyelectrolyte Layer

Alkylsilane–SiO₂ Hybrids. A Concerted Picture of Temperature Effects in Vapor Phase Functionalization

Poly(ethyleneimine) as a Passivating Agent for Ta Chemical Mechanical Planarization

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Electrochemical studies of self-assembled monolayers using impedance spectroscopy

Cited by 41 publications

References 26 publications

DNA Immobilization and Hybridization Detection by the Intrinsic Molecular Charge Using Capacitive Field-Effect Sensors Modified with a Charged Weak Polyelectrolyte Layer

DNA Immobilization and Hybridization Detection by the Intrinsic Molecular Charge Using Capacitive Field-Effect Sensors Modified with a Charged Weak Polyelectrolyte Layer

Alkylsilane–SiO2 Hybrids. A Concerted Picture of Temperature Effects in Vapor Phase Functionalization

Poly(ethyleneimine) as a Passivating Agent for Ta Chemical Mechanical Planarization

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Alkylsilane–SiO₂ Hybrids. A Concerted Picture of Temperature Effects in Vapor Phase Functionalization