Anti-ohmic nanoconductors: myth, reality and promise

Bajaj, Ashima; Ali, Md. Ehesan

doi:10.1039/d3cp00366c

Cited by 5 publications

(3 citation statements)

References 76 publications

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“…This suggests that both the PBE and HSE06 functionals result in similar electronic structures of ZGNRs, except that HSE06 shows a larger bandgap. We have studied the effect of hybrid functionals on the transport properties of molecular systems in our previous work [48]. Hybrid functionals can provide quantitative estimates of conductance, while the GGA functional can provide a qualitative understanding of the transport properties of the system.…”

Section: Spin Symmetry In Zgnrsmentioning

confidence: 99%

“…Various schemes have been proposed to modulate ZGNR's magnetic properties for different device applications, such as chemical functionalizations and substitutions, and the exploitation of quantum interference (QI) effects to control spinpolarized electron transmission [45][46][47][48][49][50][51][52][53][54]. Saraiva-Souza et al reported the observation of destructive quantum interference (DQI) features in the electron transmission spectrum by adding an imidazole donor group to the polyacetylene chain connected to the ZGNR electrodes [55].…”

Section: Introductionmentioning

confidence: 99%

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Broken edge spin symmetry induces a spin-polarized current in graphene nanoribbon

Ali,

Ali

2024

J. Phys. D: Appl. Phys.

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Zig-zag graphene nanoribbons (ZGNRs) are known to possess spin moments at the hydrogen-terminated edge carbon atoms, thus the spin-polarized electron transmission is expected while the current is longitudinally passed through the ZGNRs. However, in pristine ZGNRs, the spin-polarized transmission is not observed due to symmetric anti-parallel distributions of the spin densities between the edges. Here, the hypothesis is, any physical or chemical process that breaks such anti-parallel spin-symmetry can induce spin-polarized transmission in the ZGNRs. In this work, we have established this proof-of-concept by depositing the trimethylenemethane (TMM) radical on 6ZGNRH and investigating the quantum transport properties by employing the density functional theory in conjunction with nonequilibrium Green’s function (DFT-NEGF) method. Although TMM has a high magnetic moment (2 µB ), it does not induce magnetization in 6ZGNRH when TMM is physisorbed. But, during the chemisorption of TMM, it forms the π − π bond with the 6ZGNRH in a particular geometric configuration where the pz orbitals of carbon atoms of TMM have maximum overlap with the pz orbitals of carbon atoms of 6ZGNRH. The chemisorption of TMM transfers the spin moment to 6ZGNRH, which breaks the edge spin-symmetry of pristine 6ZGNRH. The adsorption of TMM radical results in transmission dips in the transmission spectra due to interference between localized states of TMM and 6ZGNRH states. This induces spin-polarized transmission with 60% spin-filtering efficiency (SFE) at zero bias, which can further be enhanced up to 92% by applying the bias voltage of 1.0 V.

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Section: Spin Symmetry In Zgnrsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Broken edge spin symmetry induces a spin-polarized current in graphene nanoribbon

Ali,

Ali

2024

J. Phys. D: Appl. Phys.

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“…To overcome this challenge, growing efforts have aimed at engineering the molecule’s electronic structure to enhance the molecular conductance while battling against the length-dependent decay. Ideally, reaching the reverse conductance/length trend, known as antiohmic behavior, − in single molecular wires is long thought-after for the development of novel quantum electronic technology, energy harvesting, and photosynthesis applications. In addition, long-range charge transport in molecules will play a crucial role in future nanodevices where CMOS-compatible molecules with outstanding performance and scalability are integrated.…”

Section: Introductionmentioning

confidence: 99%

No More Conductance Decay: Toward Efficient Long-Range Transport in Molecular Wires

Shiri,

Zhang,

Wang

2024

ACS Appl. Electron. Mater.

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Molecular electronics has emerged as a highly interdisciplinary field that utilizes single molecules or monolayers as functional electronic and sensing components, offering potential capabilities beyond conventional silicon-based electronics. A key mission of the field is to search for molecular candidates that can facilitate efficient charge transport over long distances. This requires overcoming the inherent poor conductivity of organic molecules and the "well-known" conductance decay with the increase in molecular length. Recent advances in molecular design and singlemolecule characterizations have sparked exciting opportunities for achieving ultrahigh and length-independent transport with a nearzero or inverted conductance attenuation coefficient in single molecular wires. To highlight this progress, this review surveys the representative molecular systems, the fundamental mechanisms, and design strategies involved in creating highly conductive long molecular wires in single-molecule junction platforms. Through elucidating both the chemical and physical properties of emerging molecular systems, we will facilitate an in-depth future investigation of promising design approaches and potential applications.

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Zero‐Bias Anti‐Ohmic Behaviour in Diradicaloid Molecular Wires

Sil,

Hamilton,

Morris

et al. 2024

Angewandte Chemie

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Open‐shell materials bearing multiple spin centres provide a key route to efficient charge transport in single‐molecule electronic devices. They have narrow energy gaps, and their molecular orbitals align closely to the Fermi level of the metallic electrodes, thus allowing efficient electronic transport and higher conductance. Maintaining and stabilising multiple open‐shell states – especially in contact with metallic electrodes – is however very challenging, generally requiring a continuous chemical or electrochemical potential to avoid self‐immolation of the open‐shell character. To overcome this issue, we designed, synthesised, and measured the conductance of a series of bis(indeno) fused acenes, where stability is imparted by a close‐shell quinoidal conformation in resonance with the diradical electronic configuration. We show here that these compounds have anti‐ohmic behaviour, with conductance increasing with increasing molecular length, at an unprecedented rate and across the entire bias window ([[EQUATION]]). Density Functional Theory (DFT) calculations support our findings, showing the rapidly narrowing HOMO‐LUMO gap, unique to these diradicaloid structures, is responsible for the observed behaviour. Our results provide a framework for achieving efficient transport in neutral compounds and demonstrate the promise that diradicaloid materials have in single‐molecule electronics, owing to their great stability and unique electronic structure.

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Anti-ohmic nanoconductors: myth, reality and promise

Abstract: The recent accomplishment in the design of molecular nanowires characterized by an increasing conductance with length have embarked the origin of extraordinary new family of molecular junctions referred to as...

Cited by 5 publications

References 76 publications

Broken edge spin symmetry induces a spin-polarized current in graphene nanoribbon

Broken edge spin symmetry induces a spin-polarized current in graphene nanoribbon

No More Conductance Decay: Toward Efficient Long-Range Transport in Molecular Wires

Zero‐Bias Anti‐Ohmic Behaviour in Diradicaloid Molecular Wires

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