Massless Dirac Fermions in ZrTe<sub>2</sub> Semimetal Grown on InAs(111) by van der Waals Epitaxy

Tsipas, Polychronis; Tsoutsou, D.; Fragkos, Sotirios; Sant, Roberto; Alvarez, Carlos; Okuno, Hanako; Renaud, Gilles; Alcotte, Reynald; Baron, T.; Dimoulas, A.

doi:10.1021/acsnano.7b08350

Cited by 93 publications

(119 citation statements)

References 47 publications

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“…Next, coming to the discussion on the electronic structure of ZrTe 2 , for the first time we report here the ARPES studies on bulk ZrTe 2 . An earlier existing only ARPES study is on monolayer thickness ZrTe 2 film deposited on InAs (111), suggesting a Dirac like linear bands at the Γ(A) point [56]. Interestingly, our DFT calculations predict a band inversion between Zr d and Te p states at the Γ(A) point, hinting at a possible nontrivial band structure in ZrTe 2 despite experimentally failing to detect any linear Dirac surface states.…”

Section: Discussionmentioning

confidence: 58%

“…Moreover, these studies report only the electronic structure of Zr(Se 1−x S x ) 2 which are semiconductors. Although several theoretical reports on ZrTe 2 predicted it to be a metal [53][54][55], so far no ARPES study exists on this compound in bulk phase confirming the same, except that a recent ARPES study on monolayer ZrTe 2 deposited on InAs (111) substrate showing linear Dirac states near the Fermi level at the Γ-point [56]. Thus, a thorough understanding of the electronic structure of ZrTe 2 has other vested interests as well, whether ZrTe 2 is another topological system like ZrTe 5 [57][58][59][60][61].…”

Section: Introductionmentioning

confidence: 97%

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Metal-chalcogen bond-length induced electronic phase transition from semiconductor to topological semimetal in ZrX2 ( X=Se and Te)

et al. 2020

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Using angle resolved photoemission spectroscopy (ARPES) and density functional theory (DFT) calculations we studied the low-energy electronic structure of bulk ZrTe2. ARPES studies on ZrTe2 demonstrate free charge carriers at the Fermi level, which is further confirmed by the DFT calculations. An equal number of hole and electron carrier density estimated from the ARPES data, points ZrTe2 to a semimetal. The DFT calculations further suggest a band inversion between Te p and Zr d states at the Γ point, hinting at the non-trivial band topology in ZrTe2. Thus, our studies for the first time unambiguously demonstrate that ZrTe2 is a topological semimetal. Also, a comparative band structure study is done on ZrSe2 which shows a semiconducting nature of the electronic structure with an indirect band gap of 0.9 eV between Γ(A) and M (L) high symmetry points. In the below we show that the metal-chalcogen bond-length plays a critical role in the electronic phase transition from semiconductor to a topological semimetal ingoing from ZrSe2 to ZrTe2. arXiv:1907.03987v1 [cond-mat.mtrl-sci]

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Section: Discussionmentioning

confidence: 58%

Section: Introductionmentioning

confidence: 97%

Metal-chalcogen bond-length induced electronic phase transition from semiconductor to topological semimetal in ZrX2 ( X=Se and Te)

et al. 2020

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“…Figure c shows the band schemes of the semimetals and semiconductors of group IVB TMDs, respectively. TiSe 2 , TiTe 2 , ZrTe 2 , and HfTe 2 show semimetal behaviors, with a small overlap between the top of the p‐orbital chalcogen valence band and the bottom of the d‐orbital transition metal conduction band. These semimetallic materials have more complex and attractive electronic behaviors and properties than other semiconductors of group IVB, such as the CDW transition and controllable superconducting transition.…”

Section: Crystal and Electronic Structuresmentioning

confidence: 99%

2D Group IVB Transition Metal Dichalcogenides

Yan

Gong

Wangyang

et al. 2018

Adv Funct Materials

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Semiconductor technology is currently impaired by the surface dangling bond of materials, which introduces scattering and interface traps. 2D materials, especially transition metal dichalcogenides (TMDs) with different main groups, have settled this issue by utilizing unique atomically smooth surfaces and van der Waals (vdW) structures. Over the past few decades, many processes for exploring new materials, manipulating physical properties, and synthesizing single crystals have been developed. Among these 2D materials, group IVB TMDs are distinguished for their splendid physical properties, including ultrahigh mobility, charge density wave, superconducting transitions, etc. Here, the recent advances in group IVB TMDs are reviewed, which offer easy access to next generation nano-, opto-, thermal-electronic, energy storage and conversion applications. Both the advantages and challenges of these studies are summarized to further clarify existing problems.such as ZrSe 2 is up to 8000 µA µm −1 , which is 10 3 times higher than that of MoS 2 . [11] Group IVB TMDs are also promising thermoelectric materials for their enhanced thermoelectric performance with a high power factor such as TiS 2 . [12][13][14][15][16] These features indicate the great potential of group IVB TMDs for adoption into electronics. In addition, group IVB TMDs show fascinating electrochemical performances as hold materials [17][18][19] or electrodes [20,21] in catalysis [22,23] and batteries [24,25] (Figure 1). A breakthrough may be introduced in nanoelectronic and energy fields for ultrahigh performances and nontoxicity of 2D group IVB TMDs.In this review, we focus on the electronic structures of 1T-phase group IVB TMDs, the abundant properties of group IVB TMDs, and their applications in electronic devices. In particular, we start with the unique crystal structures and calculated electronic structures of 2D group IVB dichalcogenides. Then, the great properties and the current studies in electronic devices are reviewed with an emphasis on recently reported transistor and photodetectors based on group IVB TMD nanosheets. In the third part, the synthesis of group IVBs nanostructures is described. We review the current approaches for the isolation of ultrathin sheets and analyze the advantages and drawbacks of various preparation methods. At last, we present the challenges and future prospects of group IVB TMDs. Crystal and Electronic StructuresThe electronic structures of 2D TMDs strongly depend on their crystal structures and d-electron counts. Another crucial feature is the partially filled d bands of transition metals. Bulk TMDs are composed of ordered stacking monolayers connected by the weak van der Waals (vdW) interaction. This kind of layered material exists multifarious in polymorphs and commonly crystallize into three different structures in 1T, 2H, and 3R phases. For group IVB TMDs, 1T phase is more stable than 2H phase in reversal of group VIB TMDs due to their lower formation energies. [23] Figure 2a,b depicts the two typical structures o...

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“…The group IVB 2D transition metal dichalcogenides (TMDs) with the chemical formula MX 2 (M = Ti, Hf, and Zr; X = S, Se, and Te) are generally stable adopting a high symmetry trigonal octahedral (1T) structure since they do not possess unpaired d electrons at the metal site that could otherwise be a source of instability. A notable exception is 1T TiSe 2 which, below 205 K makes the transition to a lower symmetry commensurate charge density wave (CDW) ground state associated with a 2 × 2 × 2 periodic lattice distortion (PLD).…”

Section: Introductionmentioning

confidence: 99%

Room Temperature Commensurate Charge Density Wave in Epitaxial Strained TiTe₂ Multilayer Films

Fragkos

Sant

Alvarez

et al. 2019

Adv Materials Inter

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Despite a large number of studies [2,3] over the years since the first discovery [7] and a couple of comprehensive reviews [8,9] the actual mechanism for PLD/CDW formation is still under debate. The most recent experimental [10][11][12][13] and theoretical [14] works focus on the large area growth of the CDW phase [13] the thickness dependence, and the possible unconventional behavior in the ultimate 2D limit of a single layer TiSe 2 . [10][11][12]14] On the other hand, the other Ti dichalcogenides namely TiS 2 and TiTe 2 did not show any clear evidence until very recently when a CDW state was reported only for 1 monolayer (ML)-thin TiTe 2 at temperatures lower than 92 K. [15] It is surprising that the CDW in TiTe 2 was found to be totally suppressed for films thicker than 1 ML, [15] unlike the case of other TMDs where 1 ML and bulk-like films both make the transition to a CDW at nearly the same temperature.The interest about TiTe 2 is continuously increasing in view of theoretical predictions [16] and more recent experimental evidence [17] about pressure induced topological phase transitions in TiTe 2 . The possibility to also manipulate superconductivity by external pressure as predicted [18] and more recently evidenced [19] in bulk TiTe 2 creates the prospect to explore the emergence of topological superconductivity in this material. In the latter work [19] it has been shown that under nonhydrostatic pressure, a CDW-like state with estimated transition temperature above room temperature (RT) appears in bulk TiTe 2 at around 0.5-1.8 GPa. These results call for a re-examination of the possibility to obtain a CDW in multilayer TiTe 2 and indeed at RT with good potential for real world applications utilizing the properties of the CDW state. These applications include a voltage-controlled oscillator device operating at room temperature, [20] fast electronic resistance switching for nonvolatile memories, [21,22] and field-effect transistor devices potentially suitable for implementation of non-Boolean logic. [23] In this paper it is shown that multilayer films (50 ML ≈ 32 nm), as well as single layer TiTe 2 epitaxially grown on InAs(111)/ Si(111) substrates by molecular beam epitaxy exhibit, in ambient pressure conditions, a CDW distortion at room temperature which is sustained up to higher temperatures, at least 400 °C, as evidenced by reflection high energy electron diffraction (RHEED) ( Figure S1, Supporting Information). The results are explained in terms of anisotropic strain imposed by the substrate.The group IVB 2D transition metal dichalcogenides are considered to be stable in the high symmetry trigonal octahedral structure due to the lack of unpaired d-electrons on the metal site. It is found that multilayer epitaxial TiTe 2 is an exception adopting a commensurate 2 × 2 × 2 charge density wave (CDW) structure at room temperature with an ABA type of stacking as evidenced by direct lattice imaging and reciprocal space mapping. The CDW is stabilized by highly anisotropic strain imposed by the substrate with an...

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Massless Dirac Fermions in ZrTe₂ Semimetal Grown on InAs(111) by van der Waals Epitaxy

Cited by 93 publications

References 47 publications

Metal-chalcogen bond-length induced electronic phase transition from semiconductor to topological semimetal in ZrX2 ( X=Se and Te)

Metal-chalcogen bond-length induced electronic phase transition from semiconductor to topological semimetal in ZrX2 ( X=Se and Te)

2D Group IVB Transition Metal Dichalcogenides

Room Temperature Commensurate Charge Density Wave in Epitaxial Strained TiTe₂ Multilayer Films

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Massless Dirac Fermions in ZrTe2 Semimetal Grown on InAs(111) by van der Waals Epitaxy

Cited by 93 publications

References 47 publications

Metal-chalcogen bond-length induced electronic phase transition from semiconductor to topological semimetal in ZrX2 ( X=Se and Te)

Metal-chalcogen bond-length induced electronic phase transition from semiconductor to topological semimetal in ZrX2 ( X=Se and Te)

2D Group IVB Transition Metal Dichalcogenides

Room Temperature Commensurate Charge Density Wave in Epitaxial Strained TiTe2 Multilayer Films

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Massless Dirac Fermions in ZrTe₂ Semimetal Grown on InAs(111) by van der Waals Epitaxy

Room Temperature Commensurate Charge Density Wave in Epitaxial Strained TiTe₂ Multilayer Films