Room temperature detection of individual molecular physisorption using suspended bilayer graphene

Detection of individual molecular adsorption, which represents the ultimate resolution of gas sensing, has rarely been realized with solid-state devices. So far, only a few studies have reported detection of individual adsorption by measuring the variation of electronic transport stemming from the charge transfer of adsorbate. We report room-temperature detection of the individual physisorption of carbon dioxide molecules with suspended bilayer graphene (BLG) based on a different mechanism. An electric field introduced by applying back-gate voltage is used to effectively enhance the adsorption rate. A unique device architecture is designed to induce tensile strain in the BLG to prevent its mechanical deflection onto the substrate by electrostatic force. Despite the negligible charge transfer from a single physisorbed molecule, it strongly affects the electronic transport in suspended BLG by inducing charged impurity, which can shut down part of the conduction of the BLG with Coulomb impurity scattering. Accordingly, we can detect each individual physisorption as a step-like resistance change with a quantized value in the BLG. We use density functional theory simulation to theoretically estimate the possible resistance response caused by Coulomb scattering of one adsorbed CO2 molecule, which is in agreement with our measurement.

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First Principle DFT Study of Electric Field Effects on the Characteristics of Bilayer Graphene

Zeitschrift für Naturforschung A ◽

10.1515/zna-2016-0231 ◽

2017 ◽

Vol 72 (1) ◽

pp. 1-7 ◽

Cited By ~ 3

Author(s):

Hassan Sabzyan ◽

Narges Sadeghpour

Keyword(s):

Charge Transfer ◽

Electric Field ◽

Density Functional ◽

Local Density ◽

Bilayer Graphene ◽

Binding Energies ◽

First Principle ◽

Electric Field Effects ◽

Field Effects ◽

Unit Cells

AbstractFirst principle density functional theory methods, local density and Perdew-Burke-Ernzerhof generalized gradient approximations with Goedecker pseudopotential (LDA-G & PBE-G), are used to study the electric field effects on the binding energy and atomic charges of bilayer graphene (BLG) at the Γ point of the Brillouin zone based on two types of unit cells (α and β) containing nC=8–32 carbon atoms. Results show that application of electric fields of 4–24 V/nm strengths reduces the binding energies and induces charge transfer between the two layers. The transferred charge increases almost linearly with the strength of the electric field for all sizes of the two types of unit cells. Furthermore, the charge transfer calculated with the α-type unit cells is more sensitive to the electric field strength. The calculated field-dependent contour plots of the differential charge densities of the two layers show details of charge density redistribution under the influence of the electric field.

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Outstanding elastic, electronic, transport and optical properties of a novel layered material C4F2: first-principles study

RSC Advances ◽

10.1039/d1ra04065k ◽

2021 ◽

Vol 11 (38) ◽

pp. 23280-23287

Author(s):

Tuan V. Vu ◽

Huynh V. Phuc ◽

Sohail Ahmad ◽

Vo Quang Nha ◽

Chu Van Lanh ◽

...

Keyword(s):

Density Functional Theory ◽

Optical Properties ◽

Electronic Transport ◽

First Principles ◽

Density Functional ◽

Single Layer ◽

Bilayer Graphene ◽

Layered Material ◽

Functional Theory ◽

First Principles Study

Motivated by transformation of AB-stacking bilayer graphene into fluorinated single-layer diamond (fluorinated diamane C4F2), we investigate the structural, elastic, electronic, transport, and optical properties of fluorinated diamane C4F2 using density functional theory.

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Back-Gate GaN Nanowire-Based FET Device for Enhancing Gas Selectivity at Room Temperature

Sensors ◽

10.3390/s21020624 ◽

2021 ◽

Vol 21 (2) ◽

pp. 624

Author(s):

Md Ashfaque Hossain Khan ◽

Ratan Debnath ◽

Abhishek Motayed ◽

Mulpuri V. Rao

Keyword(s):

Density Functional ◽

Room Temperature ◽

Gate Dielectric ◽

Molecular Models ◽

Functional Theory ◽

Back Gate ◽

Highly Sensitive ◽

Gan Nanowire ◽

Effect Transistor ◽

Gas Response

In this work, a TiO2-coated GaN nanowire-based back-gate field-effect transistor (FET) device was designed and implemented to address the well-known cross-sensitive nature of metal oxides. Even though a two-terminal TiO2/GaN chemiresistor is highly sensitive to NO2, it suffers from lack of selectivity toward NO2 and SO2. Here, a Si back gate with C-AlGaN as the gate dielectric was demonstrated as a tunable parameter, which enhances discrimination of these cross-sensitive gases at room temperature (20 °C). Compared to no bias, a back-gate bias resulted in a significant 60% increase in NO2 response, whereas the increase was an insignificant 10% in SO2 response. The differential change in gas response was explained with the help of a band diagram, derived from the energetics of molecular models based on density functional theory (DFT). The device geometries in this work are not optimized and are intended only for proving the concept.

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Photoconductivity in Vacuum Deposited Films of Silicon-Based Polymers

MRS Proceedings ◽

10.1557/proc-444-191 ◽

1996 ◽

Vol 444 ◽

Author(s):

H. Okumoto ◽

M. Shimomura ◽

N. Minami ◽

Y. Tanabe

Keyword(s):

Charge Transfer ◽

Chemical Modification ◽

Electronic Transport ◽

Hole Transport ◽

Electron Acceptors ◽

Oxygen Atmosphere ◽

Dangling Bonds ◽

Silicon Based ◽

Deposited Films

AbstractSilicon-based polymers with σconjugated electrons have specific properties; photoreactivity for microlithography and photoconductivity for hole transport materials. To explore the possibility of combining these two properties to develop photoresists with electronic transport capability, photoconductivity of polysilanes is investigated in connection with their photoinduced chemical modification. Increase in photocurrent is observed accompanying photoreaction of poly(dimethylsilane) vacuum deposited films. This increase is found to be greatly enhanced in oxygen atmosphere. Such changes of photocurrent can be explained by charge transfer to electron acceptors from Si dangling bonds postulated to be formed during photoreaction.

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On the Nature of Halide-Water Interactions: Insights from Many-Body Representations and Density Functional Theory

10.26434/chemrxiv.7613042.v2 ◽

2019 ◽

Author(s):

Brandon B. Bizzarro ◽

Colin K. Egan ◽

Francesco Paesani

Keyword(s):

Density Functional Theory ◽

Charge Transfer ◽

Molecular Orbital ◽

Density Functional ◽

Decomposition Analysis ◽

Orbital Energy ◽

Energy Decomposition Analysis ◽

Interaction Energies ◽

Many Body ◽

Functional Theory

<div> <div> <div> <p>Interaction energies of halide-water dimers, X<sup>-</sup>(H<sub>2</sub>O), and trimers, X<sup>-</sup>(H<sub>2</sub>O)<sub>2</sub>, with X = F, Cl, Br, and I, are investigated using various many-body models and exchange-correlation functionals selected across the hierarchy of density functional theory (DFT) approximations. Analysis of the results obtained with the many-body models demonstrates the need to capture important short-range interactions in the regime of large inter-molecular orbital overlap, such as charge transfer and charge penetration. Failure to reproduce these effects can lead to large deviations relative to reference data calculated at the coupled cluster level of theory. Decompositions of interaction energies carried out with the absolutely localized molecular orbital energy decomposition analysis (ALMO-EDA) method demonstrate that permanent and inductive electrostatic energies are accurately reproduced by all classes of XC functionals (from generalized gradient corrected (GGA) to hybrid and range-separated functionals), while significant variance is found for charge transfer energies predicted by different XC functionals. Since GGA and hybrid XC functionals predict the most and least attractive charge transfer energies, respectively, the large variance is likely due to the delocalization error. In this scenario, the hybrid XC functionals are then expected to provide the most accurate charge transfer energies. The sum of Pauli repulsion and dispersion energies are the most varied among the XC functionals, but it is found that a correspondence between the interaction energy and the ALMO EDA total frozen energy may be used to determine accurate estimates for these contributions. </p> </div> </div> </div>

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A Reinvestigation of the Deceptively Simple Reaction of Toluene with ●OH, and the Fate of the Benzyl Radical. I. a Combined Thermodynamic and Kinetic Study on the Competition Between ●OH Addition and Hydrogen Abstraction Reactions.

10.26434/chemrxiv.8281283.v1 ◽

2019 ◽

Author(s):

Zoi Salta ◽

Agnie M. Kosmas ◽

Marc E. Segovia ◽

Martina Kieninger ◽

Oscar Ventura ◽

...

Keyword(s):

Density Functional ◽

Room Temperature ◽

Hydrogen Abstraction ◽

Reaction Rates ◽

Composite Model ◽

Alternative Mechanism ◽

Radical Intermediate ◽

Experimental Conditions ◽

Methyl Group ◽

Benzyl Radical

This work reports density functional and composite model chemistry calculations performed on the reactions of toluene with the hydroxyl radical. Both experimentally observed H-abstraction from the methyl group and possible additions to the phenyl ring were investigated. Reaction enthalpies and heights of the barriers suggest that H-abstraction is more favorable than ●OH addition to the ring. The calculated reaction rates at room temperature and the radical-intermediate product fractions support this view. This is somehow contradictory with the fact that, under most experimental conditions, cresols are observed in a larger concentration than benzaldehyde. Since the accepted mechanism for benzaldehyde formation involves H-abstraction, a contradiction arises that begs for an explanation. In this first part of our work we give the evidences that support the preference of hydrogen abstraction over ●OH addition and suggest an alternative mechanism which shows that cresols can actually arise also from the former reaction and not only from the latter.

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