Angle-resolved photoemission studies of the band structure of Ti<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mrow><mml:mi mathvariant="normal">Se</mml:mi></mml:mrow><mml:mrow><mml:mn>2</mml:mn></mml:mrow></mml:msub></mml:mrow></mml:math>and Ti<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mrow><mml:mi mathvariant="normal">S</mml:mi></mml:mrow><mml:mrow><mml:mn>2</mml:mn></mml:mrow></mml:msub></mml:mrow

Chen, C. H.; Fabian, W.; Brown, F. C.; Woo, K. C.; Davies, Brian M.; DeLong, B.; Thompson, A. H.

doi:10.1103/physrevb.21.615

Cited by 169 publications

(46 citation statements)

References 25 publications

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“…It consists of layers of face-sharing TiS 6 octahedra with strong covalent  interaction and weak van der Waals forces between TiS 2 layers. TiS 2 has shown its potential as a promising thermoelectric material through its high power factor 2 ( ) S  at room temperature [4].…”

Section: Introductionmentioning

confidence: 99%

“…TiS 2 has shown its potential as a promising thermoelectric material through its high power factor 2 ( ) S  at room temperature [4]. However, its TE performance is limited by its high thermal conductivity, so ZT value is not optimal [5][6][7][8]. The intercalation of bismuth sulfide (BiS) as a phonon barrier layer in van der Waals gaps to form (BiS) 1.2 (TiS 2 ) 2 had become an effective way of reducing the thermal conductivity.…”

Section: Introductionmentioning

confidence: 99%

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Thermoelectric performance enhancement of (BiS)1.2(TiS2)2 misfit layer sulfide by chromium doping

et al. 2013

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Abstract:A misfit layer sulfide (BiS) 1.2 (TiS 2 ) 2 with a natural superlattice structure has been shown to be a promising thermoelectric material, but its high carrier concentration should be reduced so as to further optimize the thermoelectric performance. However, ordinary acceptor doping has not succeeded because of the non-parabolic band structure. In this paper, we have successfully doped chromium ions into the Ti sites, which can maintain or even enhance the high effective mass of electrons so as to effectively improve ZT value. X-ray diffraction analysis, coupled with X-ray photoelectron spectroscopy, shows that chromium has been substituted into titanium sites in TiS 2 layers and confirms its ionic state. The chromium doping has successfully reduced the carrier concentration with the subsequent reduction of electrical conductivity. Unlike other acceptor dopants (alkaline earth metals), chromium also enhances Seebeck coefficient and the effective mass, which can possibly be attributed to the formation of additional resonant states near Fermi level. Though the power factor does not improve, the significant reduction in the electronic part of the thermal conductivity leads to a measurable improvement in ZT.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Thermoelectric performance enhancement of (BiS)1.2(TiS2)2 misfit layer sulfide by chromium doping

et al. 2013

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“…ARPES measurements revealed the band structure, with some of the details that still remain controversial. In the normal state, above the CDW state, TiSe 2 is either a semimetal [3,4] or a semiconductor [5,6] with a small indirect gap. The Se 4p valence band is at the Brillouin zone center Γ while the Ti 3d conduction band forms pockets at the Brillouin zone boundary L. In the CDW state the Se 4p bands become backfolded.…”

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confidence: 99%

Evolution of the charge density wave state in CuxTiSe2

et al. 2012

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We present scanning tunneling microscopy and spectroscopy measurements of the charge-density wave state in 1T -TiSe2, Cu0.05TiSe2 and Cu0.06TiSe2 single crystals. Topography images at 4.2 K reveal that the charge density waves are present in all samples studied, although the amplitude of the charge modulation decreases with the Cu-doping. Moreover, the chiral phase of the charge density wave is preserved also in Cu-doped samples. Tunneling spectroscopy shows that there is only a partial gap in the pure compound, with bands crossing the Fermi surface. In the Cu-doped samples the system becomes more metallic due to the increase of the chemical potential.PACS numbers: 71.45. Lr, 74.55.+v, 72.80.Ga, 73.22.Gk INTRODUCTIONTransition metal dichalcogenides are quasi-twodimensional, highly anisotropic compounds that often show instabilities to charge density wave (CDW) formation at low temperature. The chalcogenide atoms form two parallel layers with the atoms in a hexagonal arrangement. The transition metal atoms exist in between these two layers. In the 1T -type crystal structure the transition metal atoms are octahedrally coordinated. In particular, 1T -TiSe 2 undergoes a CDW phase transition below 200 K with a formation of a commensurate (2a 0 × 2a 0 × 2c 0 ) superlattice [1] that involves a small ionic displacement( 0.08Å), and it is accompanied by a phonon softening [2]. ARPES measurements revealed the band structure, with some of the details that still remain controversial. In the normal state, above the CDW state, TiSe 2 is either a semimetal [3,4] or a semiconductor [5,6] with a small indirect gap. The Se 4p valence band is at the Brillouin zone center Γ while the Ti 3d conduction band forms pockets at the Brillouin zone boundary L. In the CDW state the Se 4p bands become backfolded. The origin of the CDW state remains still a matter of controversy up to date. The CDW transition is not likely to originate from nesting since parallel sheets of the Fermi surface were not detected by ARPES measurements. The proposed scenarios are an indirect Jahn-Teller effect [7], an exciton insulator mechanism [8] or an exciton-phonon driven CDW [9]. Being a material with bands very close to the Fermi level, TiSe 2 is a unique candidate for the excitonic mechanism. Unlike many semiconductors, TiSe 2 has a large number of states close to E F that makes it favorable for collective phenomena to take place. On the other hand, the small total number of carriers yields to a poorly screened Coulomb interaction, so the system is unstable to formation of excitons. However, the softening of the L − 1 mode has been observed in x-ray experiments and it might have some relevance to the CDW formation as well [2]. The discovery of superconductivity upon intercalation of Cu has further attracted the attention to this material [10]. With Cu doping it was found that the CDW transition temperature drops and the superconductivity sets in at a doping x = 0.04 with a highest superconducting transition temperature of 4.15 K occurring at x = 0.08. With ...

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“…The band gap of TiS 2 was investigated many times both experimentally [57][58][59][60][61][62][63][64][65] and theoretically [5,11,[66][67][68][69][70][71][72][73][74]. Experimental studies suggest that TiS 2 is a semiconductor with a small indirect band gap between 0.18 eV [63] and 0.56 eV [65].…”

Section: Band Structurementioning

confidence: 99%

Density Functional Theory Evaluated for Structural and Electronic Properties of 1T-Li _x TiS₂ and Lithium Ion Migration in 1T-Li_0.94TiS₂

Werth

Volgmann

Islam

et al. 2017

Zeitschrift Für Physikalische Chemie

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Abstract:In many applications it has been found that the standard generalized gradient approximation (GGA) does not accurately describe weak chemical bond and electronic properties of solids containing transition metals. In this work, we have considered the intercalation material 1T-Li x TiS 2 (0 ≤ x ≤ 1) as a model system for the evaluation of the accuracy of GGA and corrected GGA with reference to the availabile experimental data. The influence of two different dispersion corrections (D3 and D-TS) and an on-site Coulomb repulsion term (GGA + U) on the calculated structural and electronic properties is tested. All calculations are based on the Perdew-Burke-Ernzerhof (PBE) functional. An effective U value of 3.5 eV is used for titanium. The deviation of the calculated lattice parameter c for TiS 2 from experiment is reduced from 14 % with standard PBE to −2 % with PBE + U and Grimme's D3 dispersion correction. 1T-TiS 2 has a metallic ground state at PBE level whereas PBE + U predicts an indirect gap of 0.19 eV in agreement with experiment. The 7 Li chemical shift and quadrupole coupling constants are in reasonable agreement with the experimental data only for PBE + U-D3. An activation energy of 0.4 eV is calculated with PBE + U-D3 for lithium migration via a tetrahedral interstitial site. This result is closer to experimental values than the migration barriers previously obtained at LDA level. The proposed method PBE + U-D3 gives a reasonable description of structural and electronic properties of 1T-Li x TiS 2 in the whole range 0 ≤ x ≤ 1.

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Angle-resolved photoemission studies of the band structure of TiSe2and TiS2

Cited by 169 publications

References 25 publications

Thermoelectric performance enhancement of (BiS)1.2(TiS2)2 misfit layer sulfide by chromium doping

Thermoelectric performance enhancement of (BiS)1.2(TiS2)2 misfit layer sulfide by chromium doping

Evolution of the charge density wave state in CuxTiSe2

Density Functional Theory Evaluated for Structural and Electronic Properties of 1T-Li _x TiS₂ and Lithium Ion Migration in 1T-Li_0.94TiS₂

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Angle-resolved photoemission studies of the band structure of TiSe2and TiS2

Cited by 169 publications

References 25 publications

Thermoelectric performance enhancement of (BiS)1.2(TiS2)2 misfit layer sulfide by chromium doping

Thermoelectric performance enhancement of (BiS)1.2(TiS2)2 misfit layer sulfide by chromium doping

Evolution of the charge density wave state in CuxTiSe2

Density Functional Theory Evaluated for Structural and Electronic Properties of 1T-Li x TiS2 and Lithium Ion Migration in 1T-Li0.94TiS2

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Density Functional Theory Evaluated for Structural and Electronic Properties of 1T-Li _x TiS₂ and Lithium Ion Migration in 1T-Li_0.94TiS₂