Organic Monolayer Protected Topological Surface State

Yang, Hung-Hsiang; Chu, Yu-Hsun; Lu, Chien-Rong; Butler, C. J.; Sankar, Raman; Chou, F. C.; Lin, Minn-Tsong

doi:10.1021/acs.nanolett.5b02811

Cited by 8 publications

(12 citation statements)

References 35 publications

(60 reference statements)

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“…The Drude conductance retains a similar scattering rate, which indicates the organic thin film layers are homogenous and induce no extra impurity scattering. This is consistent with previous spectroscopy studies, which showed that the surface states dispersion is robust to adsorbed molecules [57][58][59][60]. Nevertheless, in contrast to these works that increased the chemical potential by depositing organics [57][58][59][60], we lower it towards the Dirac point.…”

supporting

confidence: 93%

“…This is consistent with previous spectroscopy studies, which showed that the surface states dispersion is robust to adsorbed molecules [57][58][59][60]. Nevertheless, in contrast to these works that increased the chemical potential by depositing organics [57][58][59][60], we lower it towards the Dirac point. Samples were kept in a desiccator with reduced moisture for the next four months and then re-measured by the THz spectrometer.…”

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confidence: 93%

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Tuning and stabilizing topological insulator Bi2Se3 in the intrinsic regime by charge extraction with organic overlayers

Ireland

Salehi

et al. 2016

Applied Physics Letters

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In this work, we use charge extraction via organic overlayer deposition to lower the chemical potential of topological insulator Bi 2 Se 3 thin films into the intrinsic (bulk-insulating) regime. We demonstrate the tuning and stabilization of intrinsic topological insulators at high mobility with low-cost organic films. With the protection of the organic charge extraction layers tetrafluorotetracyanoquinodimethane(F4TCNQ) or tris(acetylacetonato)cobalt(III) (Co(acac) 3 ), the sample is stable in the atmosphere with chemical potential ~135 meV above the Dirac point (85 meV below the conduction band minimum, well within the topological insulator regime) after four months, which is an extraordinary level of environmental stability. The Co complex demonstrates the use of an organometallic for modulating TI charge density. The mobility of surface state electrons is enhanced as high as ~2000 cm 2 /Vs. Even at room temperature, a true topologically insulating state is realized and stabilized for months' exposure to the atmosphere.Topological insulators (TIs) are exotic bulk insulators which host helical metallic surface states on their boundaries [1,2]. Spin direction is locked to momentum and "up" and "down" spins travel in opposite directions without backscattering, which makes TIs possibly ideal platforms for future low-dissipation spintronics applications [3]. Spin plasmons generated in the topological surface states may be used for the next generation of plasmonic devices [4]. Topological surface states also display a host of interesting fundamental physics phenomena including a topological magneto-electric effect and axion electrodynamics [5, 6,7]. Majorana fermions may be realized in the vortex core through a proximity effect between superconductors and intrinsic TIs [8]. Their non-abelian statistical nature may serve as a foundation for future fault-tolerant quantum computers [9]. All of the above phenomena can only be realized in intrinsic (i.e. bulk-insulating) TIs.However, most TIs are either doped in the bulk or quickly lose their intrinsic properties by exposure to air [10,11,12]. Chemical dedoping has been shown to be effective in reducing the carrier density. Unfortunately, disorder introduced by dedoping tends to pin impurity states at the chemical potential and decrease the mobility significantly [13,14,15]. Furthermore, these chemically compensated TIs suffer from strong aging effects from the atmospheres [12]. O 2 was 2 either shown to reduce the carrier density [16,17,18] or not to have a noticeable effect [19,20], while H 2 O and CO were shown to raise the chemical potential to the conduction band and create topologically trivial Rashba states [21,22], which interferes the transport signal from topological surface states. H 2 O can even serve as an electron donor for layered chalcogenide semiconductors even without prominent surface reactions [23,24]. Therefore, an effective method to keep the sample in the bulk-insulating regime is still lacking. Gating is an effective method to lower the chemical p...

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supporting

confidence: 93%

supporting

confidence: 93%

Tuning and stabilizing topological insulator Bi2Se3 in the intrinsic regime by charge extraction with organic overlayers

Ireland

Salehi

et al. 2016

Applied Physics Letters

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“…Such a self-assembled PTCDA layer can also be used as a buffer layer to protect the topological surface states (TSSs) of Bi2Se3, which exhibits a Dirac cone-like dispersion similar to G [69]. …”

Section: Ptcda On Layered Substratesmentioning

confidence: 99%

Van Der Waals Heterostructures between Small Organic Molecules and Layered Substrates

Huang

Wang

et al. 2016

Crystals

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Two dimensional atomic crystals, like grapheme (G) and molybdenum disulfide (MoS 2 ), exhibit great interest in electronic and optoelectronic applications. The excellent physical properties, such as transparency, semiconductivity, and flexibility, make them compatible with current organic electronics. Here, we review recent progress in the understanding of the interfaces of van der Waals (vdW) heterostructures between small organic molecules (pentacene, copper phthalocyanine (CuPc), perylene-3,4,9,10-tetracarboxylic dianhydride (PTCDA), and dioctylbenzothienobenzothiophene (C 8 -BTBT)) and layered substrates (G, MoS 2 and hexagonal boron nitride (h-BN)). The influences of the underlying layered substrates on the molecular arrangement, electronic and vibrational properties will be addressed.

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“…The creation of hybrid molecule‐TI interfaces has several advantages, namely (i) the electric field‐driven ionization process can change the molecules charge state only by integer numbers, i.e., by adding or removing single electrons. This results, because of the high degree of charge localization typical of molecules, in a well‐defined sequence of discrete states generated by strong Coulomb repulsions, (ii) molecules can be placed onto TI surfaces without perturbing their topological states by scattering, (iii) contrary to conventional doping, i.e., adatoms, the hybridization of molecules with topological surfaces is reduced, thus preserving their functionality, and (iv) their distribution can be precisely controlled through self‐assembly processes …”

mentioning

confidence: 99%

“…More recently, it has been demonstrated that all these limitations can be overcome at once by using molecules as building blocks [14][15][16][17][18][19]. Molecules have already been successfully used in the past to create hybrid heterostructures with functionalities going beyond those of their constituents [20,21].…”

mentioning

confidence: 99%

Single Electron Gating of Topological Insulators

et al. 2016

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The effective gating of topological insulators is demonstrated, through the coupling of molecules to their surface. By using electric fields, they allow for dynamic control of the interface charge state by adding or removing single electrons. This process creates a robust transconductance bistability resembling a single-electron transistor. These findings make hybrid molecule/topological interfaces functional elements while at the same time pushing miniaturization to its ultimate limit.

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Organic Monolayer Protected Topological Surface State

Cited by 8 publications

References 35 publications

Tuning and stabilizing topological insulator Bi2Se3 in the intrinsic regime by charge extraction with organic overlayers

Tuning and stabilizing topological insulator Bi2Se3 in the intrinsic regime by charge extraction with organic overlayers

Van Der Waals Heterostructures between Small Organic Molecules and Layered Substrates

Single Electron Gating of Topological Insulators

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