Electronic and optical properties of van der Waals heterostructures of g-GaN and transition metal dichalcogenides

Cui, Zhen; Ren, Kai; Zhao, Yiming; Wang, Xia; Shu, Huabing; Yu, Jin; Sun, Minglei

doi:10.1016/j.apsusc.2019.06.207

Cited by 198 publications

(56 citation statements)

References 63 publications

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“…The calculated lattice parameters for 2D α-PtO2 (GaN) are the following: lattice constant, a ~ 3.168 (3.248) Å, bond length, dB ~ 2.07 (1.875) Å, and buckling height, dH ~ 1.865 (0.0) Å. These lattice parameters are wellaligned with other theoretical and experimental studies [18], [44]- [47][26], [31], [42]. For stacking the 2D layers, 2D PtO2 (α-phase) is assumed as substrate layer and 2D GaN is vertically placed on top of that layer.…”

Section: A Structural Propertiessupporting

confidence: 79%

“…Among them, 2D GaN stacked with TMDs, and transition metal oxides (TMO) outperforms due to their visible driven PWS capability with cross-plane spatial carrier separation (SCS). Besides, MoS2/GaN, phosphorene/GaN, GeC/GaN, BAs/GaN, and BP/GaN are all show tunable electronic, optical properties with tunable PWS band edges due to stacking variations and external perturbation (biaxial strain, and cross-plane electric field) [29], [31]- [33]. However, to our best knowledge, the vdW PtO2/GaN heterobilayer is not studied yet for the PWS application, though 2D PtO2 and 2D GaN possess astounding intrinsic and tunable optoelectronic properties.…”

Section: Introductionmentioning

confidence: 99%

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Potential Visible-Light Driven PtO₂/GaN vdW Hetero-Bilayer Photocatalysts for Water Splitting Using First-Principles

Khan

Islam

et al. 2021

IEEE Access

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Novel two-dimensional (2D) PtO2/GaN van der Waals (vdW) hetero-bilayers (HBL) are studied here for photocatalytic water splitting (PWS) application under first-principles density functional theory (DFT). We proposed six HBLs due to the atomic orientational variations and two of them are found dynamically stable confirmed by phonon dispersion curves. The two stable HBLs, HBL1, and HBL6 also show negative binding energy depicted by the interlayer distance-dependent binding energy curves. Among them, HBL1 has the lowest binding energy, suggesting the exothermic practicability of the material. Electronically both materials show a visible ranged indirect bandgap of ~2.65 (2.69) eV for HBL 1 (HBL6), lowered by ~2 times compared to their intrinsic constituents (2D PtO2, 2D GaN). The bandgaps also have type-II band orientation, which is highly required for efficient spatial carrier separation in photocatalytic water splitting (PWS) applications. The optical properties of the HBLs were also calculated, and it's found that the HBLs have ~2×10 5 cm -1 of perovskite material-like absorption coefficient in the visible spectrum, a key requirement for efficient photocatalysis. Reflectivity is as low as ~7 % in the visible spectrum, suggesting the low-loss nature of the materials. Photocatalytic band-edges with type-II band alignments show sufficient kinetic overpotential for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) in both HBLs, suggesting effective water-splitting capacity. Moreover, we have explored the biaxial strain-induced tunability of the electronic bandgap, absorption coefficients, and photocatalytic band edges. They all found responsive due to homogeneous biaxial strain and show bandgap-lowering, absorption coefficient visible shifting, and band-edges tuning from compressive to tensile strains in the -6 % to +6% range. These studies suggest that the novel PtO2/GaN vdW layered material can be a probable efficient material for visible-lightdriven photocatalytic water-splitting technology.INDEX TERMS 2D PtO2/GaN, hetero-bilayer, Van der Waals (vdW) concept, first-principles density functional theory (DFT), optoelectronic property, photocatalytic water splitting.

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Section: A Structural Propertiessupporting

confidence: 79%

Section: Introductionmentioning

confidence: 99%

Potential Visible-Light Driven PtO₂/GaN vdW Hetero-Bilayer Photocatalysts for Water Splitting Using First-Principles

Khan

Islam

et al. 2021

IEEE Access

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“…Transition metal dichalcogenides (TMDs): sulphides, selenides or tellurides of tungsten or molybdenum are well known for their lubricating properties [1]. Hexagonal MoS 2 and WS 2 are compounds with unique characteristics originating from an extreme degree of crystalline anisotropy and, due to this, the TMDs have gained considerable attention in the research community for a variety of mechanical, electronic and optical applications [2][3][4][5]. Despite the greater resistance to high temperature oxidation of WS 2 [6], MoS 2 has been more widely studied due to its lower cost and lubricating performance in a vacuum and dry atmosphere, Initially, MoS 2 coatings were deposited by burnishing [7], electrochemical process [8] and plasma vapour deposition [7][8][9][10][11][12] techniques.…”

Section: Introductionmentioning

confidence: 99%

Synthesis and structural properties of Mo-S-N sputtered coatings

Kannur

Yaqub

Huminiuc

et al. 2020

Applied Surface Science

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Transition-metal-dichalcogenide coatings provide low friction because of characteristic low shear strength along the basal plane of the lamellar structure; however, the material can easily degrade through exfoliation and poor adhesion to the metallic substrates. In this work, an innovative approach was employed to improve the coating's adhesion. A secondary plasma source was used during deposition to generate an additional charged particle flux which was directed to the growing film independently of the magnetron cathode. Therefore, Mo-S-N solid lubricant films were deposited by DCMS from a single molybdenum disulphide (MoS 2 ) target in a reactive atmosphere. Nitrogen was introduced during the deposition with increasing partial pressures, resulting in a high N 2 content in the doped films (37 at. %). The variation in incident ion energy and flux of energetic species bombarding the growing film allows for the control of the S/Mo ratio through selective re-sputtering of sulphur from the film. The S/Mo ratio was progressively increased to the range of 1.2-1.8, having gradient from metallic layer upto-the lubricious sulphide. Combining the ion bombardment with nitrogen incorporation, cohesive critical load (Lc1) reached 38N, 10 times more than MoS 2 coating. Observation using HRTEM revealed an amorphous structure and strong bonding with the substrate.

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“…Researchers have also done a lot of theoretical investigation on the structure, electric, optical, and magnetic properties of two-dimensional GaN. Through chemical modification, 20 adsorptions, [21][22][23] doping, 24,25 vacancy defect, 26 heterosructure, 27 and other methods to control the band gap and atomic structure of GaN monolayer, they show that GaN monolayer will have significant performance in the next generation of nanodevices. [28][29][30] Superior advantages of GaN monolayer also make it be an ideal cathode material for solar energy converters based on PETE.…”

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confidence: 99%

Structural and electronic properties of Cs‐adsorbed GaN monolayer and bilayer based on first principles

Liu

2021

Int J Energy Res

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A negative electron affinity photocathode can be obtained by adsorbing Cs on the emission layer surface of photocathode, which greatly improves the number of electrons escaped and the quantum efficiency. Based on first principles, this paper studies the structural and electronic properties of Cs-adsorbed GaN monolayer and bilayer. The results reveal that the Cs-adsorbed GaN monolayer is the most stable when Cs atom is adsorbed at T Ga site. There is a significant charge transfer between Cs atom and GaN monolayer, and the difference in electronegativity makes electrons of Cs atom transfer to GaN monolayer system. Cs adsorption can reduce band gap, work function, and electron affinity, which is conducive to the escape of electrons and improvement of quantum efficiency. Cs adsorption is helpful for tuning optical properties of GaN monolayer. For the GaN bilayer, greater stability and lower work function make the Cs adsorbed above the top layer of GaN bilayer be more beneficial to the improvement of photoelectric performance. Novelty StatementBased on first principles, this paper studies the structure and electric properties of Cs-adsorbed GaN monolayer and bilayer. Cs adsorption can reduce band gap, work function, and electron affinity, which is conducive to the escape of electrons and improvement of quantum efficiency. And for the GaN bilayer, greater stability and lower work function make the Cs adsorbed above the top layer of GaN bilayer be more beneficial to the improvement of photoelectric performance. K E Y W O R D Scharge transfer, Cs adsorption, first principles, GaN bilayer, GaN monolayer | INTRODUCTIONCs-activated GaN photocathode has been applied in flame detection, 1 corona detection, 2 ultraviolet communication, 3 and other fields. Because Cs activation plays an important role in reducing surface barrier and work function, it helps the photocathode achieve a negative electron affinity state which is beneficial to photoelectron emission. 4 In recent years, there are many theoretical and experimental studies on Cs-absorbed GaN surface reported successively. The GaN photocathode prepared by Machuca et al. 5 had a quantum efficiency (QE) of 50% at 310 nm after Cs activation. Norton et al 6 achieved a high-quality GaN emission layer with 40% QE at 185 nm by using Cs treatment. Du et al 7 discussed the adsorption mechanism of Cs based on first principles and showed that Cs adsorption can reduce

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Electronic and optical properties of van der Waals heterostructures of g-GaN and transition metal dichalcogenides

Cited by 198 publications

References 63 publications

Potential Visible-Light Driven PtO₂/GaN vdW Hetero-Bilayer Photocatalysts for Water Splitting Using First-Principles

Potential Visible-Light Driven PtO₂/GaN vdW Hetero-Bilayer Photocatalysts for Water Splitting Using First-Principles

Synthesis and structural properties of Mo-S-N sputtered coatings

Structural and electronic properties of Cs‐adsorbed GaN monolayer and bilayer based on first principles

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