Thin film MoS_2 nanocrystal based ultraviolet photodetector

Alkis, Sabri; Öztaş, Tuğba; Aygün, Levent E.; Bozkurt, Fatih; Okyay, Ali Kemal; Ortaç, Bülend

doi:10.1364/oe.20.021815

Cited by 52 publications

(38 citation statements)

References 21 publications

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“…1L-MoS 2 FETs have both unipolar [2] and ambipolar [14] transport characteristics with mobilities>500cm 2 V −1 s −1 [15] and on-off current ratios up to 10 9 [16]. This combination of electrical and optical properties suggests that 1L-MoS 2 is a promising candidate for novel optoelectronic devices, such as 2d photodetectors [17][18][19], and light-emitting devices operating in the visible range.…”

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confidence: 99%

Electroluminescence in Single Layer MoS₂

et al. 2013

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We detect electroluminescence in single layer molybdenum disulphide (MoS2) field-effect transistors built on transparent glass substrates. By comparing absorption, photoluminescence, and electroluminescence of the same MoS2 layer, we find that they all involve the same excited state at 1.8eV. The electroluminescence has pronounced threshold behavior and is localized at the contacts. The results show that single layer MoS2, a direct band gap semiconductor, is promising for novel optoelectronic devices, such as 2-dimensional light detectors and emitters. Here, we report electrically excited luminescence in 1L-MoS 2 FETs, and study the underlying emission mechanism. We find that the electroluminescence occurs via hot carriers and is localized in the contacts region. The observed photoluminescence and electroluminescence arise from the same excited state at 1.8eV. Molybdenum disulphide (MoS1L-MoS 2 crystals are produced by micromechanical cleavage of bulk MoS 2 (Structure Probe Inc.-SPI, Natural Molybdenite) on 100nm SiO 2 . As for the case of graphene [20], interference allows visibility and counting the number of layers, Fig.1a. Due to the different dielectric properties, an optimum thickness of 100nm SiO 2 is well suited for MoS 2 [21]. The presence of monolayers is then confirmed by performing PL measurements, Fig.1b. The PL spectrum of 1L-MoS 2 exhibits two bands at 2eV and 1.8eV (Fig.1b) associated with excitonic transitions at the K point of the Brillouin zone[4]. The energy difference of 0.2eV has been attributed to the degeneracy breaking of the valence band due to spin-orbit coupling [4,7,8,22]. As compared to bulk MoS 2 , Fig.1b, 1L-MoS 2 does not have a peak at 1.4eV [3,4], associated with the indirect band gap [12]. In addition 1L-MoS 2 exhibits a stronger PL intensity compared to bulk MoS 2 [3, 4] due to the direct band gap. Another evidence for 1L-MoS 2 comes from the analysis of the Raman spectrum, Fig.1d. The peak at∼385cm −1 corresponds to the in plane (E 1 2g ) mode [23], while that at ∼404 cm −1 is attributed to the out of plane (A 1g ) mode [23]. The E 1 2g mode softens and A 1g mode stiffens with increasing layer thickness[23], similar to what happens for other layered materials, where the bond distance changes with number of layers [24]. The frequency difference between these two modes can be used as a signature of 1L-MoS 2 [23].1L-MoS 2 flakes are then transferred onto glass substrates by using a poly(methyl methacrylate) (PMMA) based transfer technique, similar to that previously used to transfer graphene onto optical fibre cores [25]. This process involves spin coating two layers of 495K PMMA and one layer of 950K PMMA on the substrate where flakes are deposited. The samples are subsequently immersed in de-ionized (DI) water at 90 • C for 1h, resulting in the detachment of the polymer film, due to the intercalation of water at the polymer-SiO 2 interface. MoS 2 flakes stick to the PMMA, and can thus be removed from the original substrate and mechanically transferred onto glass substrates [2...

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Electroluminescence in Single Layer MoS₂

et al. 2013

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“…12 In this study, we repeat the same procedure except for the solvent type, which is methanol instead of water; we recognize that the obtained NS have different morphologies. The use of the PLA technique to crystalline 2H-MoS 2 powder in methanol generates both colloidal 2D and 3D MoS 2 NS.…”

Section: ■ Results and Discussionmentioning

confidence: 99%

“…The optical absorption spectrum of colloidal MoS 2 NS shows a minimum optical absorption feature at 1300 nm and also prominent shoulders at 265 nm, and the strong rising absorption edge shifts toward the UV region. Compared to the optical properties of 3D MoS 2 NS from the PLA technique in DI water, 12 laser-generated MoS 2 NS have broadband optical absorption properties tailoring from the NIR region to the UV region, and therefore, MoS 2 NS can be considered as a prime candidate for various photonics and optoelectronics applications.…”

Section: ■ Results and Discussionmentioning

confidence: 99%

Synthesis of Colloidal 2D/3D MoS₂ Nanostructures by Pulsed Laser Ablation in an Organic Liquid Environment

et al. 2014

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Two-dimensional MoS 2 nanosheets (2D MoS 2 NS) and fullerene-like MoS 2 nanostructures (3D MoS 2 NS) with varying sizes are synthesized by nanosecond laser ablation of hexagonal crystalline 2H-MoS 2 powder in organic solution (methanol). Structural, chemical, and optical properties of MoS 2 NS are characterized by optical microscopy, scanning electron microscopy, transmission electron microscopy, X-ray diffraction, and Raman and UV−vis−near infrared absorption spectroscopy techniques.Results of the structural analysis show that the obtained MoS 2 NS mainly present a layered morphology from micrometer to nanometer sized surface area. Detailed analysis of the product also proves the existence of inorganic polyhedral fullerene-like 3D MoS 2 NS generated by pulsed laser ablation in methanol. The possible factors which may lead to formation of both 2D and 3D MoS 2 NS in methanol are examined by ab initio calculations and shown to correlate with vacancy formation. The hexagonal crystalline structure of MoS 2 NS was determined by XRD analysis. In Raman spectroscopy, the peaks at 380.33 and 405.79 cm −1 corresponding to the E 1 2g and A 1g phonon modes of MoS 2 were clearly observed. The colloidal MoS 2 NS solution presents broadband absorption edge tailoring from the UV region to the NIR region. Investigations of MoS 2 NS show that the one-step physical process of pulsed laser ablation−bulk MoS 2 powder interaction in organic solution opens doors to the formation of "two scaled" micrometer-and nanometer-sized layered and fullerene-like morphology MoS 2 structures.

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“…Typically, flexible substrates require low-temperature processes. For this purpose, photodetectors (PDs) based on organic semiconductors 1 and colloidal semiconductor nanocrystals [2][3][4] have been investigated. In addition, thin films of wide bandgap inorganic semiconductors for ultraviolet PDs are sought.…”

Section: Introductionmentioning

confidence: 99%

Metal-semiconductor-metal ultraviolet photodetectors based on gallium nitride grown by atomic layer deposition at low temperatures

et al. 2014

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Abstract. Proof-of-concept, first metal-semiconductor-metal ultraviolet photodetectors based on nanocrystalline gallium nitride (GaN) layers grown by low-temperature hollow-cathode plasma-assisted atomic layer deposition are demonstrated. Electrical and optical characteristics of the fabricated devices are investigated. Dark current values as low as 14 pA at a 30 V reverse bias are obtained. Fabricated devices exhibit a 15× UV/VIS rejection ratio based on photoresponsivity values at 200 nm (UV) and 390 nm (VIS) wavelengths. These devices can offer a promising alternative for flexible optoelectronics and the complementary metal oxide semiconductor integration of such devices.

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Thin film MoS_2 nanocrystal based ultraviolet photodetector

Cited by 52 publications

References 21 publications

Electroluminescence in Single Layer MoS₂

Electroluminescence in Single Layer MoS₂

Synthesis of Colloidal 2D/3D MoS₂ Nanostructures by Pulsed Laser Ablation in an Organic Liquid Environment

Metal-semiconductor-metal ultraviolet photodetectors based on gallium nitride grown by atomic layer deposition at low temperatures

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Thin film MoS_2 nanocrystal based ultraviolet photodetector

Cited by 52 publications

References 21 publications

Electroluminescence in Single Layer MoS2

Electroluminescence in Single Layer MoS2

Synthesis of Colloidal 2D/3D MoS2 Nanostructures by Pulsed Laser Ablation in an Organic Liquid Environment

Metal-semiconductor-metal ultraviolet photodetectors based on gallium nitride grown by atomic layer deposition at low temperatures

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Product

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Electroluminescence in Single Layer MoS₂

Electroluminescence in Single Layer MoS₂

Synthesis of Colloidal 2D/3D MoS₂ Nanostructures by Pulsed Laser Ablation in an Organic Liquid Environment