Influence of hydrogen addition to an Ar plasma on the structural properties of TiO<sub>2−x</sub> thin films deposited by RF sputtering

Luciu, I.; Bartali, Ruben; Laidani, N.

doi:10.1088/0022-3727/45/34/345302

Cited by 59 publications

(41 citation statements)

References 53 publications

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“…These results confirm that the hydrogen gas evidently interacts with the MoS 2 surface even though the surface is thought to be inert unlike the catalytically active edge sites [27]. It is notable that an existence of carbon after the H 2 annealing implies that a formation of the hydrocarbon (C-H bonds) [28] was inevitable during the hydrogenation at the condition of Fig. 1(c) [18].…”

Section: −10supporting

confidence: 59%

Hydrogenation-induced atomic stripes on the2H−MoS2surface

et al. 2015

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We report that the hydrogenation of a single crystal 2H -MoS 2 induces a novel-intermediate phase between 2H and 1T phases on its surface, i.e., the large-area, uniform, robust, and surface array of atomic stripes through the intralayer atomic-plane gliding. The total energy calculations confirm that the hydrogenation-induced atomic stripes are energetically most stable on the MoS 2 surface between the semiconducting 2H and metallic 1T phase. Furthermore, the electronic states associated with the hydrogen ions, which is bonded to sulfur anions on both sides of the MoS 2 surface layer, appear in the vicinity of the Fermi level (E F ) and reduces the band gap. This is promising in developing the monolayer-based field-effect transistor or vanishing the Schottky barrier for practical applications. Thickness-dependent indirect-to-direct band-gap transition of molybdenum disulfide (MoS 2 ) [1,2] and a successful realization of the field-effect transistor (FET) using a singlelayer (1L-) MoS 2 [3] have renewed interests of transition-metal dichalcogenides. This has also boosted the development of two-dimensional (2D) materials for the high performance flexible electronic and optoelectronic devices [4,5]. For a preparation of 1L-MoS 2 , the top-down exfoliation methods such as mechanical exfoliation [1][2][3]6], liquid exfoliation by sonication in a good solvent [7], and chemical exfoliation through lithium (Li) intercalation [8,9] are conventionally used. Among several exfoliation methods, the Li intercalation makes MoS 2 nanosheets only in the nanometer-sized metallic 1T phase [10,11], while other methods usually in the semiconducting 2H phase [1][2][3]. Moreover, without intercalating Li, the 1T phase can be intentionally introduced in the 2H matrix by using a high dose of incident electron beam during heating 1L-MoS 2 , which accompanies intermediate phases as precursors [12]. This 2H/1T phase transition can be realized by gliding sulfur (S) and/or molybdenum (Mo) atomic planes with a change of the d-electron counts [13]. A miniaturization of 2D devices [14] plus a local induction of the metallic 1T phase [11][12][13] controlled (i.e., stripe-patterned) hydrogenation on the MoS 2 monolayer has been theoretically shown to be metallic [19].In this Rapid Communication, we find a novel-intermediate phase between 2H and 1T phases, which consists of a highlyregular surface array of atomic stripes on the MoS 2 surface, and determine its materialization condition in the hydrogenation of a single crystal MoS 2 . This finding motivates one to investigate the interaction between hydrogen and the MoS 2 surface based on a combination of the transmission electron microscopy (TEM), scanning photoelectron microscopy (SPEM), angleresolved photoelectron spectroscopy (ARPES), and firstprinciples calculation. Further, we indicate that the electronic states associated with the emerging phase appear near the Fermi level (E F ) and reduce the band gap, promising in vanishing the Schottky barrier.For the hydrogenation, natural single cryst...

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Section: −10supporting

confidence: 59%

Hydrogenation-induced atomic stripes on the2H−MoS2surface

et al. 2015

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“…6A) shows two intense peaks at 458. 4 Additional shoulders at 457.0 and 462.6 eV were also clearly identified by peak fitting procedure and correspond to the Ti 3+ cations [55,57]. In the case of the W 4d 5/2 region (Fig.…”

Section: Effects Of Composition and Sintering Conditions On Site Occumentioning

confidence: 71%

Design of SrTiO₃-Based Thermoelectrics by Tungsten Substitution

et al. 2015

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Among n-type oxide thermoelectrics, donor-substituted strontium titanates, prepared in highlyreducing conditions, show particularly attractive thermoelectric figure of merit. High electrical conductivity, combined with outstanding redox tolerance and perovskite-phase stability of these materials, also make them prospective candidates for SOFC anode components. This work represents a first attempt to process strontium titanate ceramics with significant W for Ti substitution, and to assess their relevant defect chemistry-related aspects, electrical and thermal properties, seeking mainly highlyperforming oxide thermoelectrics. Combined XRD/XPS/SEM/EDS studies of SrTi 1-x W x O 3±δ (x=0.01-0.10), prepared by a conventional solid state route, demonstrated that the maximum solubility of tungsten corresponds to 3-5% mol, depending on firing conditions and other composition changes.Separation of tungsten-containing phases on a submicro-and nanoscale level and formation of core-shell microstructures was confirmed for x≥0.06, suggesting possibilities for tuning the thermal and electrical conductivities. Titanium cations are substituted predominantly by W 6+ and partially by W 5+ . High electrical conductivity and Seebeck coefficient resulted in maximum power factor of ~0.5 mW×m -1 ×K -2 for SrTi 0.99 W 0.01 O 3±δ ; maximum ZT values, observed in the case of x=0.01-0.06, amounted to 0.18-0.24 at 1173-1273 K. Co-substitution in Sr(Ti,Nb,W)TiO 3±δ materials showed good prospects for boosting thermoelectric performance in titanates, predominantly by significant reduction of the thermal conductivity.

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“…The main 2p 3/2 and 2p 1/2 doublets appear at 458.6 and 464.3 eV, respectively, with a spin-orbit splitting energy of 5.7 eV. [34][35][36] It is also noteworthy that, for both composition sets, the binding energies of the main 2p 3/2 sharp peak are slightly shifted to higher energies with increasing Ta content, likely due to the local structural distortions. In the case of tantalum, the high-resolution spectra were recorded in both 4f and 4d core level regions ( Fig 4B and 4C, respectively).…”

Section: Chemistry Of Materialsmentioning

confidence: 92%

Boosting Thermoelectric Performance by Controlled Defect Chemistry Engineering in Ta-Substituted Strontium Titanate

Yaremchenko¹,

Populoh

Patrício³

et al. 2015

Chem. Mater.

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Inspired by recent research results that have demonstrated appealing thermoelectric performance of A-site cation-deficient titanates, this work focuses on detailed analysis of the changes in performance promoted by altering the defect chemistry mechanisms. The series of cation-stoichiometric SrTi 1-x Ta x O 3±δ and A-site deficient Sr 1-x/2 Ti 1-x Ta x O 3-δ compositions (0.05≤x≤ 0.30) with cubic perovskite-like structure were selected to demonstrate the defect chemistry engineering approaches, which result in promising electric and thermal properties. High power factors were observed in compositions where appropriate concentration of the charge carriers and their mobility were attained by presence of strontium-and oxygen vacancies and suppressed formation of the oxygen-rich layers. Noticeable deviations from stoichiometric oxygen content were found to decrease the lattice thermal conductivity, suggesting good phonon scattering ability for oxygen vacancies, vacant A-sites and oxygen-excessive defects, while the effect from donor substitution on the thermal transport was less pronounced. The obtained guidelines for the defect chemistry engineering in donor-substituted strontium titanates open new possibilities for boosting the thermoelectric performance, especially if followed by complementary microstructural design to further promote electrical and thermal transport.

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Influence of hydrogen addition to an Ar plasma on the structural properties of TiO_2−x thin films deposited by RF sputtering

Cited by 59 publications

References 53 publications

Hydrogenation-induced atomic stripes on the2H−MoS2surface

Hydrogenation-induced atomic stripes on the2H−MoS2surface

Design of SrTiO₃-Based Thermoelectrics by Tungsten Substitution

Boosting Thermoelectric Performance by Controlled Defect Chemistry Engineering in Ta-Substituted Strontium Titanate

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Influence of hydrogen addition to an Ar plasma on the structural properties of TiO2−x thin films deposited by RF sputtering

Cited by 59 publications

References 53 publications

Hydrogenation-induced atomic stripes on the2H−MoS2surface

Hydrogenation-induced atomic stripes on the2H−MoS2surface

Design of SrTiO3-Based Thermoelectrics by Tungsten Substitution

Boosting Thermoelectric Performance by Controlled Defect Chemistry Engineering in Ta-Substituted Strontium Titanate

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Product

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Influence of hydrogen addition to an Ar plasma on the structural properties of TiO_2−x thin films deposited by RF sputtering

Design of SrTiO₃-Based Thermoelectrics by Tungsten Substitution