Vapour transport deposition of fluorographene oxide films and electro-optical device applications

Rahul Sharma; Ravi K. Biroju; Ofer Sinai; Hagai Cohen; Krishna Rani Sahoo; Vlada Artel; Hadas Alon; Adi Levi; A. Subrahmanyam; Wolfgang Theis; Doron Naveh; Tharangattu N. Narayanan

doi:10.1016/j.apmt.2018.08.015

Vapour transport deposition of fluorographene oxide films and electro-optical device applications

Rahul Sharma, Ravi K. Biroju, Ofer Sinai, Hagai Cohen, Krishna Rani Sahoo, Vlada Artel, Hadas Alon, Adi Levi, A. Subrahmanyam, Wolfgang Theis, Doron Naveh, Tharangattu N. Narayanan

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Abstract

Fluorographene is one of the most interesting 2D materials owing to its span of electronic properties, from a conductor to wide-gap insulator, controlled by the compositional carbon to fluorine ratio. Unlike the chemically inert graphene, fluorographene is recognized for its rich chemistry, particularly at ambient, allowing tailoring its physical properties. Here, we report on single step, catalyst free, wafer-scale synthesis of fluorographene oxide (FGO) ultra-thin films (∼4 nm thickness) by physical vapour deposition. The FGO, possessing 7% fluorine content, comprises few-nanometer domains of sp²-sp³ carbon with high thermal stability, as confirmed by several analytical methods. We show that FGO can be utilized as an active hetero-layer on a few-layer MoS₂ field effect transistor (FET), significantly improving the performance of MoS₂ optoelectronic devices with an extended spectral response towards the near infrared and responsivity of up to 6 A/W. The FGO-MoS₂ band alignment, as derived from the measured work function of FGO (4.69 eV), indicates a plausible photoconductive gain mechanism with a fast transit time of holes mediated by FGO quasi-continuous defect states.

Original language	English
Pages (from-to)	387-395
Number of pages	9
Journal	Applied Materials Today
Volume	13
DOIs	https://doi.org/10.1016/j.apmt.2018.08.015
State	Published - Dec 2018

Bibliographical note

Publisher Copyright:
© 2018 Elsevier Ltd

Funding

Further investigation of the show dark and bright field (respectively) STEM images of the FGO transferred onto the TEM Cu grid (see the experimental section and supporting information for details). Insets show the lattice pattern of the single FGO flake, corresponding to the hexagonal lattice of sp 2 -sp 3 carbon domains and their grain sizes in the as-grown FGO was performed by high angle annular dark field scanning transmission electron microscopy (HAADF-STEM). Fig. 2 (a-b) sp 2 carbon in the labelled domains. The variation in the HAADF intensity within flakes is attributed to the thickness uniformity of FGO films and its resulting electron scattering. Fig. 2 (c) depicts a high-resolution HAADF-STEM image of a single flake with the sp 2 (graphene like) and sp 3 (diamond like) carbon domains labelled, and the corresponding bright field STEM image is shown Fig. 2 (d). The hexagonal lattice diffraction pattern of sp 2 carbon is clearly observed in the FFT of the rectangular marked portion in Fig. 2 (d) (left inset in Fig. 2 (c)), while other marked portions correspond to sp 3 carbon sites within a single FGO flake. HAADF-STEM imaging confirms the number of atomic layers in FGO films to be 6–7 layers (see supporting information, Fig. S3). This thickness estimate is also supported by the XPS results below. TNN, RS, and KRS acknowledge the funding support from Tata Institute of Fundamental Research (TIFR), India. TNN also acknowledges DST-SERB, India for the funding support in the form of extramural research grant for working on van der Waals solids based structures (EMR/2017/000513). OS is grateful for the help of Ms. Michal Wasserman with the electrical measurements and microscopy of some of the samples. DN thanks the Israel Science Foundation for grant No. 1055/15. RKB acknowledges Marie-Sklodowska-Curie individual fellowship under EU H2020 programme (H2020_IF_2017; Grant Number: 750929) and postdoctoral fellowship from SERB-NPDF (PDF/2016/002642), India. Authors also thank Dr. Balakrishna Ananthoju and Prof. Robert Dryfe, The University of Manchester for the Raman streamline mapping measurements of FG samples. Authors also thank Dr. Kanchan Garai and his students at TIFR-H for helping us in conducting AFM measurements. TNN dedicates this article to his beloved teacher (Late) Prof. V.C. Kuriakose, CUSAT, India.

Funders	Funder number
DST-SERB	EMR/2017/000513
SERB-NPDF	PDF/2016/002642
Horizon 2020 Framework Programme	750929
University of Manchester
Tata Institute of Fundamental Research
Israel Science Foundation	1055/15

Keywords

Electronic transport
Field effect transistor
Fluorographene oxide
Photodetector
Physical vapour deposition
Wafer scale synthesis

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10.1016/j.apmt.2018.08.015

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title = "Vapour transport deposition of fluorographene oxide films and electro-optical device applications",

abstract = "Fluorographene is one of the most interesting 2D materials owing to its span of electronic properties, from a conductor to wide-gap insulator, controlled by the compositional carbon to fluorine ratio. Unlike the chemically inert graphene, fluorographene is recognized for its rich chemistry, particularly at ambient, allowing tailoring its physical properties. Here, we report on single step, catalyst free, wafer-scale synthesis of fluorographene oxide (FGO) ultra-thin films (∼4 nm thickness) by physical vapour deposition. The FGO, possessing 7% fluorine content, comprises few-nanometer domains of sp2-sp3 carbon with high thermal stability, as confirmed by several analytical methods. We show that FGO can be utilized as an active hetero-layer on a few-layer MoS2 field effect transistor (FET), significantly improving the performance of MoS2 optoelectronic devices with an extended spectral response towards the near infrared and responsivity of up to 6 A/W. The FGO-MoS2 band alignment, as derived from the measured work function of FGO (4.69 eV), indicates a plausible photoconductive gain mechanism with a fast transit time of holes mediated by FGO quasi-continuous defect states.",

keywords = "Electronic transport, Field effect transistor, Fluorographene oxide, Photodetector, Physical vapour deposition, Wafer scale synthesis",

author = "Rahul Sharma and Biroju, {Ravi K.} and Ofer Sinai and Hagai Cohen and Sahoo, {Krishna Rani} and Vlada Artel and Hadas Alon and Adi Levi and A. Subrahmanyam and Wolfgang Theis and Doron Naveh and Narayanan, {Tharangattu N.}",

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doi = "10.1016/j.apmt.2018.08.015",

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AU - Sharma, Rahul

AU - Biroju, Ravi K.

AU - Sinai, Ofer

AU - Cohen, Hagai

AU - Sahoo, Krishna Rani

AU - Artel, Vlada

AU - Alon, Hadas

AU - Levi, Adi

AU - Subrahmanyam, A.

AU - Theis, Wolfgang

AU - Naveh, Doron

AU - Narayanan, Tharangattu N.

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AB - Fluorographene is one of the most interesting 2D materials owing to its span of electronic properties, from a conductor to wide-gap insulator, controlled by the compositional carbon to fluorine ratio. Unlike the chemically inert graphene, fluorographene is recognized for its rich chemistry, particularly at ambient, allowing tailoring its physical properties. Here, we report on single step, catalyst free, wafer-scale synthesis of fluorographene oxide (FGO) ultra-thin films (∼4 nm thickness) by physical vapour deposition. The FGO, possessing 7% fluorine content, comprises few-nanometer domains of sp2-sp3 carbon with high thermal stability, as confirmed by several analytical methods. We show that FGO can be utilized as an active hetero-layer on a few-layer MoS2 field effect transistor (FET), significantly improving the performance of MoS2 optoelectronic devices with an extended spectral response towards the near infrared and responsivity of up to 6 A/W. The FGO-MoS2 band alignment, as derived from the measured work function of FGO (4.69 eV), indicates a plausible photoconductive gain mechanism with a fast transit time of holes mediated by FGO quasi-continuous defect states.

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Vapour transport deposition of fluorographene oxide films and electro-optical device applications

Abstract

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Keywords

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