Electronic properties of single-layer tungsten disulfide on epitaxial graphene on silicon carbide

Forti, Stiven; Rossi, Antonio; Büch, Holger; Cavallucci, Tommaso; Bisio, Francesco; Sala, Alessandro; Menteş, Tevfik Onur; Locatelli, Andrea; Magnozzi, Michele; Canepa, M.; Müller, Kathrin; Link, Stefan; Starke, Ulrich; Tozzini, Valentina; Coletti, Camilla

doi:10.1039/c7nr05495e

Cited by 47 publications

(67 citation statements)

References 53 publications

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“…This value is in good agreement with our calculation (431 meV) and other theoretical predictions [23-26, 45, 46]. The same size of the splitting was obtained in spinintegrated measurements for SL WS 2 on different substrates [11,17,39] as well as on bulk samples [47], while other references report slightly higher values [48,49].…”

Section: Fig 1 (A)supporting

confidence: 92%

Spin Structure of K Valleys in Single-Layer WS2 on Au(111)

et al. 2018

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The spin structure of the valence and conduction bands at the K and K' valleys of single-layer WS2 on Au(111) is determined by spin-and angle-resolved photoemission and inverse photoemission. The bands confining the direct band gap of 1.98 eV are out-of-plane spin polarized with spin-dependent energy splittings of 417 meV in the valence band and 16 meV in the conduction band. The sequence of the spin-split bands is the same in the valence and in the conduction bands and opposite at the K and the K' high-symmetry points. The first observation explains "dark" excitons discussed in optical experiments, the latter points to coupled spin and valley physics in electron transport. The experimentally observed band dispersions are discussed along with band structure calculations for a freestanding single layer and for a single layer on Au(111).

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Section: Fig 1 (A)supporting

confidence: 92%

Spin Structure of K Valleys in Single-Layer WS2 on Au(111)

et al. 2018

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“…We believe that the clean ohmic contact obtained with our approach is at the basis of the fast response time of our devices. Furthermore the epitaxial relation in our heterostack 9 could have a positive impact as well.…”

Section: Resultsmentioning

confidence: 89%

“…1(b)) using a growth process similar to that reported elsewhere. 9,11 However, in the present work, the growth recipe was adapted in order to obtain a continuous WS 2 monolayer film. Sulfurization of tungsten trioxide (WO 3 ) powder (Sigma Aldrich, 99.995%) was carried out in a horizontal hot-wall furnace (Lenton PTF).…”

Section: Ws 2 Synthesismentioning

confidence: 99%

“…7 In the vicinity of those points it shows a remarkable splitting of the valence band due to spin-orbit coupling. 8,9 Because of symmetry selection rules, spin polarized carriers can be promoted in the conduction band using polarized light. 7,10,11 Its optical properties can be used for photodetection to enhance the response of graphene.…”

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confidence: 99%

“…11 The WS 2 layer synthesized in this way is azimuthally aligned with the underlying EG. 9 The precise band alignment and the atomically sharp interfaces of this heterostack are crucial to control the optoelectronic properties of the full structure. In this work, we demonstrate an entirely scalable hybrid WS 2 /EG photodetector with a maximum photoresponsivity R ∼220 A W −1 under continuous-wave illumination and a −3 dB bandwidth of 250 Hz.…”

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confidence: 99%

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Patterned tungsten disulfide/graphene heterostructures for efficient multifunctional optoelectronic devices

et al. 2018

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One of the major issues in graphene-based optoelectronics is to scale-up high-performing devices. In this work, we report an original approach for the fabrication of efficient optoelectronic devices from scalable tungsten disulfide (WS)/graphene heterostructures. Our approach allows for the patterned growth of WS on graphene and facilitates the realization of ohmic contacts. Photodetectors fabricated with WS on epitaxial graphene on silicon carbide (SiC) present, when illuminated with red light, a maximum responsivity R ∼220 A W, a detectivity D* ∼2.0 × 10 Jones and a -3 dB bandwidth of 250 Hz. The retrieved detectivity is 3 orders of magnitude higher than that obtained with graphene-only devices at the same wavelength. For shorter illumination wavelengths we observe a persistent photocurrent with a nearly complete charge retention, which originates from deep trap levels in the SiC substrate. This work ultimately demonstrates that WS/graphene optoelectronic devices with promising performances can be obtained in a scalable manner. Furthermore, by combining wavelength-selective memory, enhanced responsivity and fast detection, this system is of interest for the implementation of 2d-based data storage devices.

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