scholarly journals First-Principles Study of the Contact Resistance at 2D Metal/2D Semiconductor Heterojunctions

2020 ◽  
Vol 10 (8) ◽  
pp. 2731 ◽  
Author(s):  
Michel Houssa ◽  
Ruishen Meng ◽  
Valery Afanas’ev ◽  
André Stesmans
Keyword(s):  
Contact Resistance ◽  
First Principles ◽  
Density Functional ◽  
Functional Theory ◽  
Nanoelectronic Devices ◽  
Device Applications ◽  
Mos2 Monolayers ◽  
Contact Symmetry ◽  
Non Equilibrium Green’S Function ◽  
Theoretical Results

The high contact resistance at metal/two-dimensional (2D) semiconductor junctions is a major issue for the integration of 2D materials in nanoelectronic devices. We review here recent theoretical results on the contact resistance at lateral heterojunctions between graphene or 1T-MoS2 with 2H-MoS2 monolayers. The transport properties at these junctions are computed using density functional theory and the non-equilibrium Green’s function method. The contact resistance is found to strongly depend on the edge contact symmetry/termination at graphene/2H-MoS2 contacts, varying between about 2 × 102 and 2 × 104 Ω∙μm. This large variation is correlated to the presence or absence of dangling bond defects and/or polar bonds at the interface. On the other hand, the large computed contact resistance at pristine 1T/2H-MoS2 junctions, in the range of 3–4 × 104 Ω.μm, is related to the large electron energy barrier (about 0.8 eV) at the interface. The functionalization of the metallic 1T-MoS2 contact by various adsorbates is predicted to decrease the contact resistance by about two orders of magnitude, being very promising for device applications.

First-Principles Study of Triangle Terarylene as a Possible Optical Molecular Switch

2011 ◽  
Vol 311-313 ◽  
pp. 526-529
Author(s):  
Cai Juan Xia ◽  
Han Chen Liu ◽  
Ji Xin Yin
Keyword(s):  
First Principles ◽  
Density Functional ◽  
Molecular Switch ◽  
Optical Switches ◽  
Functional Theory ◽  
Closed Ring ◽  
Potential Applications ◽  
Homo Lumo ◽  
Non Equilibrium Green’S Function ◽  
Theoretical Results

Using non-equilibrium Green’s function formalism combined with first-principles density functional theory, we investigate the electronic transport properties of a triangle terarylene(open- and closed-ring forms) optical molecular switch. The influence of the HOMO-LUMO gaps and the spatial distributions of molecular orbitals on the quantum transport through the molecular device is discussed. Theoretical results show that the conductance of the closed-ring is 3-8 times larger than that of open-ring, which expect that this system can be one of good candidates for optical switches due to this unique advantage, and may have some potential applications in future molecular circuit.

scholarly journals Electronic structure, transport, and collective effects in molecular layered systems

2017 ◽  
Vol 8 ◽  
pp. 2094-2105 ◽  
Author(s):  
Torsten Hahn ◽  
Tim Ludwig ◽  
Carsten Timm ◽  
Jens Kortus
Keyword(s):  
Master Equation ◽  
Density Functional ◽  
Copper Phthalocyanine ◽  
Pure Copper ◽  
Mean Field ◽  
Collective Effects ◽  
Functional Theory ◽  
Master Equation Approach ◽  
Device Applications ◽  
Non Equilibrium Green’S Function

The great potential of organic heterostructures for organic device applications is exemplified by the targeted engineering of the electronic properties of phthalocyanine-based systems. The transport properties of two different phthalocyanine systems, a pure copper phthalocyanine (CoPc) and a flourinated copper phthalocyanine–manganese phthalocyanine (F16CoPc/MnPc) heterostructure, are investigated by means of density functional theory (DFT) and the non-equilibrium Green’s function (NEGF) approach. Furthermore, a master-equation-based approach is used to include electronic correlations beyond the mean-field-type approximation of DFT. We describe the essential theoretical tools to obtain the parameters needed for the master equation from DFT results. Finally, an interacting molecular monolayer is considered within a master-equation approach.

Cyclodextrins Stabilize TOPO-(CdSe)ZnS Quantum Dots In Water

2004 ◽  
Vol 823 ◽  
Author(s):  
Jun Feng ◽  
Yong-Hyun Kim ◽  
S. B. Zhang ◽  
Shi-You Ding ◽  
Melvin P. Tucker ◽  
...  
Keyword(s):  
Density Functional Theory ◽  
Quantum Dots ◽  
First Principles ◽  
Density Functional ◽  
Water Soluble ◽  
Hydroxyl Group ◽  
Functional Theory ◽  
Chemical Action ◽  
Coordinate Bond ◽  
Device Applications

AbstractChemical action between cyclodextrins (CDs) and TOPO-(CdSe)ZnS quantum dots (QDs) generates a water-soluble solution of CD-QDs. Hydrophobic TOPO molecules on surface of the QDs are compatible to thread through the pockets of CDs and make the hydroxyl group on end of CDs to approach the ZnS surface, and then cause the interaction between ZnS and the hydroxyls. In this paper, Photoluminescence of the γ-CD-QD solution appeared about 15 nm of red movement compared with that of the QDs in hexane; 58% replacement of the crystal coordinate bond of Zn-S with that of Zn-O in the ZnS shell was demonstrated by using first-principles density functional theory and the red shift of the photoluminescence of CD-QDs; and –0.11eV of the energy gain of the exchange model was calculated by using an effective mass (EM) model. CD-QDs will provide water-soluble QDs with conjugational group for biology and molecule-device applications.

An Ab Initio Study on Negative Differential Resistance in Pyrrole Trimer Molecular Device

2010 ◽  
Vol 152-153 ◽  
pp. 931-934
Author(s):  
Cai Juan Xia ◽  
Han Chen Liu ◽  
Qiu Ping Wang
Keyword(s):  
Electronic Transport ◽  
First Principles ◽  
Negative Differential Resistance ◽  
Density Functional ◽  
Differential Resistance ◽  
Resonance Peak ◽  
Molecular Device ◽  
Transmission Resonance ◽  
Functional Theory ◽  
Theoretical Results

The electronic transport properties of pyrrole trimer sandwiched between two electrodes are investigated by using nonequilibrium Green’s function formalism combined first-principles density functional theory. Theoretical results show that the system manifests negative differential resistance (NDR) behavior. A detailed analysis of the origin of negative differential resistance has been given by observing the shift in transmission resonance peak across the bias window with varying bias voltage.

Electronic and optical properties of AlN under pressure: DFT calculations

2017 ◽  
Vol 31 (02) ◽  
pp. 1650255
Author(s):  
Sahar Javaheri ◽  
Arash Boochani ◽  
Manuchehr Babaeipour ◽  
Sirvan Naderi
Keyword(s):  
Optical Properties ◽  
Electronic Properties ◽  
Dielectric Function ◽  
First Principles ◽  
Density Functional ◽  
Functional Theory ◽  
Zinc Blende ◽  
Rocksalt Phase ◽  
Optical And Electronic Properties ◽  
Theoretical Results

Structural, elastic, optical, and electronic properties of wurtzite (WZ), zinc-blende (ZB), and rocksalt (RS) structures of AlN are investigated using the first-principles method and within the framework of density functional theory (DFT). Lattice parameters, bulk modulus, shear modulus, Young’s modulus, and elastic constants are calculated at zero pressure and compared with other experimental and theoretical results. The wurtzite and zinc-blende structures have a transition to rocksalt phase at the pressures of 12.7 GPa and 14 GPa, respectively. The electronic properties are calculated using both GGA and EV-GGA approximations; the obtained results by EV-GGA approximation are in much better agreement with the available experimental data. The RS phase has the largest bandgap with an amount of 4.98 eV; by increasing pressure, this amount is also increased. The optical properties like dielectric function, energy loss function, refractive index, and extinction coefficient are calculated under pressure using GGA approximation. Inter-band transitions are investigated using the peaks of imaginary part of the dielectric function and these transitions mainly occur from N-2[Formula: see text] to Al-3[Formula: see text] levels. The results show that the RS structure has more different properties than the WZ and ZB structures.

WATER EFFECT ON HIGH-PRESSURE ELASTICITY OF OLIVINE, WADSLEYITE AND RINGWOODITE IN Mg2SiO4 BY FIRST-PRINCIPLES

2012 ◽  
Vol 26 (19) ◽  
pp. 1250106 ◽  
Author(s):  
WEI LIU ◽  
LI-YUN TIAN ◽  
JI-JUN ZHAO ◽  
HONG LIU ◽  
LEI LIU ◽  
...  
Keyword(s):  
High Pressure ◽  
Water Content ◽  
First Principles ◽  
Density Functional ◽  
Water Effect ◽  
Functional Theory ◽  
Seismic Properties ◽  
Hydration Effect ◽  
Theoretical Results ◽  
Water Contents

The hydration effects of water on the high-pressure elastic properties of three Mg 2 SiO 4 polymorphs have been investigated using first-principles simulation density functional theory. The effect of water incorporation was simulated by considering Mg 2 SiO 4 crystals with water contents of 0, 1.65 and 3.3 wt%. With increasing water content, the calculated bulk/shear modulus and sound velocities decrease and their pressure derivatives tend to increase. Thus the hydration effect becomes less obvious at higher pressure. The bulk velocity contrasts from olivine to wadsleyite and from wadsleyite to ringwoodite are found to decrease after water incorporation. Our theoretical results indicate that water content and partition around the phase boundaries have profound impact on the structural and seismic properties of the mantle.

The image charge effect and vibron-assisted processes in Coulomb blockade transport: a first principles approach

Nanoscale ◽  
2015 ◽  
Vol 7 (45) ◽  
pp. 19231-19240 ◽  
Author(s):  
A. M. Souza ◽  
I. Rungger ◽  
U. Schwingenschlögl ◽  
S. Sanvito
Keyword(s):  
Quantum Transport ◽  
First Principles ◽  
Coulomb Blockade ◽  
Density Functional ◽  
Image Charge ◽  
Functional Theory ◽  
Master Equation Approach ◽  
Image Charge Effect ◽  
Coulomb Blockade Regime ◽  
Non Equilibrium Green’S Function

We present a combination of density functional theory and of both non-equilibrium Green's function formalism and a Master equation approach to accurately describe quantum transport in molecular junctions in the Coulomb blockade regime.

FIRST-PRINCIPLES STUDY ON PHOTOSWITCHING BEHAVIOR IN SINGLE MOLECULE JUNCTION

2018 ◽  
Vol 25 (03) ◽  
pp. 1850070 ◽  
Author(s):  
BAO-AN BIAN ◽  
YA-PENG ZHENG ◽  
PEI-PEI YUAN ◽  
BIN LIAO ◽  
YU-QIANG DING
Keyword(s):  
Single Molecule ◽  
First Principles ◽  
Density Functional ◽  
Molecular Switch ◽  
Functional Theory ◽  
Current Voltage ◽  
Molecule Junction ◽  
Single Molecule Junction ◽  
Close Form ◽  
Non Equilibrium Green’S Function

We carry out first-principles calculations based on density functional theory and non-equilibrium Green’s function to investigate the electronic transport properties of a diarylethene-based molecule sandwiched between two Au electrodes. This molecular switch can be reversed between open and close forms by using light stimulation. We analyze the switch behavior of these two forms through the current–voltage curves, transmission spectra and molecular projected self-consistent Hamiltonian. It has been found that the current of the close form is significantly larger than the open form, and there is a large and stable switch ratio in a wide bias window. This result indicates that this molecule can become one of the good candidates for optical molecular switch in the future.

First-principle calculations of the structure and elastic properties of GaAs under pressure

2009 ◽  
Vol 87 (2) ◽  
pp. 153-159 ◽  
Author(s):  
Hong-Ling Cui ◽  
Fen Luo ◽  
Xiang-Rong Chen ◽  
Guang-Fu Ji
Keyword(s):  
First Principles ◽  
Density Functional ◽  
First Principle ◽  
Pressure Derivative ◽  
Functional Theory ◽  
Plane Wave Method ◽  
First Principle Calculations ◽  
Zinc Blende ◽  
Debye Temperatures ◽  
Theoretical Results

A first-principles plane-wave method with the ultrasoft pseudopotential scheme in the framework of density functional theory is performed to calculate the lattice parameters, the bulk modulus B0 and its pressure derivative B0' of the zinc-blende GaAs (ZB–GaAs), rocksalt GaAs (RS–GaAs), CsCl–GaAs, NiAs–GaAs, and wurtzite GaAs (WZ–GaAs). We also calculate the phase transition pressures between different phases, Debye temperatures, and the anisotropies. Our results are consistent with other theoretical results.

EFFECT OF TORSION ANGLE ON THE RECTIFYING PERFORMANCE IN THE DONOR-BRIDGE-ACCEPTOR SINGLE MOLECULAR DEVICE

2012 ◽  
Vol 11 (04) ◽  
pp. 735-743 ◽  
Author(s):  
CAI-JUAN XIA ◽  
YING-TANG ZHANG ◽  
DE-SHENG LIU
Keyword(s):  
Electronic Transport ◽  
First Principles ◽  
Torsion Angle ◽  
Density Functional ◽  
Coupling Effect ◽  
Molecular Devices ◽  
Molecular Device ◽  
Functional Theory ◽  
Homo Lumo ◽  
Theoretical Results

By applying nonequilibrium Green's function formalism combined with first-principles density functional theory, we investigate the effect of torsion angle on the rectifying performance in the donor-bridge-acceptor single molecular device. The influence of HOMO–LUMO gaps and the spatial distributions of molecular orbitals on the electronic transport through the molecular device are discussed in detail. The theoretical results show that the torsion angle plays an important role in the rectifying behavior of such devices. By changing the torsion angle, namely changing the magnitude of the intermolecular coupling effect, a different rectifying behavior can be observed in these systems. The results can provide fundamental guidelines for the design of functional molecular devices to a certain extent.

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