Temperature controlled 1T/2H phase ratio modulation in mono- and a few layered MoS2 films

Pradhan, Gobinda; Sharma, Ashwini Kumar

doi:10.1016/j.apsusc.2019.02.218

Cited by 35 publications

(18 citation statements)

References 41 publications

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“…When the pressure is low (e.g., 0.8 Pa), the number of crystal nuclei per unit volume is large, and the bonding between crystal grains is not dense, resulting in high surface roughness. As the pressure increases, voids are reduced to increase the compactness and uniformity of the films, to smooth the surfaces, and lower the roughness [40]. The To investigate the grain growth and crystal structure of the MoS 2 films, we analyzed the peak half width of the (202) plane of MoS 2 on the basis of Bragg's equation (Equation 1), the cubic system distance in Equation 2, and Scherrer's equation (Equation 3), which can be used to calculate the interplanar spacing (d), lattice constant (a), and average grain size (D) [35], respectively:…”

Section: Resultsmentioning

confidence: 99%

“…When the pressure is low (e.g., 0.8 Pa), the number of crystal nuclei per unit volume is large, and the bonding between crystal grains is not dense, resulting in high surface roughness. As the pressure increases, voids are reduced to increase the compactness and uniformity of the films, to smooth the surfaces, and lower the roughness [40]. The surface morphology of the MoS 2 films directly affects the diffuse scattering, absorption, and transmission of incident light, which are key to their different optical band gaps.…”

Section: Resultsmentioning

confidence: 99%

“…In Equation 4, B is constant values, hν is the optical energy and the absorption coefficient ∂ is calculated by the Equation (5), where T is the transmittance and d is the films thickness [37,40]. Figure 5b shows the relationship between the (∂hv) 2 and hv of the MoS 2 films.…”

Section: Resultsmentioning

confidence: 99%

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Effect of Deposition Pressure on the Microstructure and Optical Band Gap of Molybdenum Disulfide Films Prepared by Magnetron Sputtering

et al. 2019

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MoS2 films were prepared via magnetron sputtering under different deposition pressures, and the effects of deposition pressure on the crystal structure, surface morphology, and optical properties of the resulting films were investigated. The results show that the crystallinity of the films first increases and then decreases with increasing pressure. The surface of the films prepared by magnetron sputtering is dense and uniform with few defects. The deposition pressure affects the grain size, surface morphology, and optical band gap of the films. The films deposited at a deposition pressure of 1 Pa revealed remarkable crystallinity, a 30.35 nm grain size, and a 1.67 eV optical band gap. Given the large electronegativity difference between MoS2 molecules and weak van der Waals forces between layers, the MoS2 films are prone to defects at different deposition pressures, causing the exciton energy near defects to decrease and the modulation of the surrounding band.

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Section: Resultsmentioning

confidence: 99%

“…When the pressure is low (e.g., 0.8 Pa), the number of crystal nuclei per unit volume is large, and the bonding between crystal grains is not dense, resulting in high surface roughness. As the pressure increases, voids are reduced to increase the compactness and uniformity of the films, to smooth the surfaces, and lower the roughness [40]. The surface morphology of the MoS 2 films directly affects the diffuse scattering, absorption, and transmission of incident light, which are key to their different optical band gaps.…”

Section: Resultsmentioning

confidence: 99%

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Effect of Deposition Pressure on the Microstructure and Optical Band Gap of Molybdenum Disulfide Films Prepared by Magnetron Sputtering

et al. 2019

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“…Using Scherrer's formula, the grain size in 1 T and 2H phases is 6.2 nm and 5.2 nm in O 0 2 respectively, which is 6.2 nm for 2H phase in O 40 -MoS 2 . However, 1 T MoS 2 is not stable and 1 T to 2H phase transition happens by annealing above 300 °C [15]. The S atoms may acquire enough energy to overcome the energy barrier and shift to the 2H phase sites [16].…”

Section: Methodsmentioning

confidence: 99%

O Plasma Treatment Enhanced Room Temperature Ferromagnetism in MoS2

Xie

Wang

et al. 2021

J Supercond Nov Magn

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MoS 2 is a typical two-dimensional material with promising optical and electrical properties. The realization of ferromagnetism in MoS 2 is important for its applications in semiconductor spintronics. A facile technique should be developed to induce the ferromagnetism in MoS 2 , and the possible extrinsic contribution should be avoided. In this paper, flower-like MoS 2 nanostructures were fabricated by the hydrothermal method. X-ray diffraction spectra show the 1 T/2H mixed phases of as-prepared MoS 2 nanostructures, which changes to pure 2H structure after the O plasma treatment. Raman spectra confirm the existence of Mo-O bonding, which is further confirmed by the X-ray photoelectron spectra after the O plasma treatment. Magnetization measurements at 300 K show the weak ferromagnetism in the as-prepared MoS 2 , with saturated ferromagnetic magnetization of 0.0012 emu/g. After the O plasma treatment, the weak ferromagnetism is strongly enhanced with saturated ferromagnetic magnetization of 0.0343 emu/g. First principle calculation has been performed to disclose the possible origin of ferromagnetism. Significant overlapping between the density of states of O and Mo, or O and S has been observed. The magnetic contribution from Mo and S is negligible, while O takes the main role for the enhanced ferromagnetism.

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“…8 Single and multilayer thin films of MoS 2 have interesting properties such as thickness-dependent band gap, 9 high carrier mobility, 10 large surface-to-volume-ratio, 11 strong spin-valley coupling, 12 chemical stability, and high mechanical flexibility. 13,14 The monolayer of MoS 2 shows a direct energy band gap ($ 1.9 eV), whereas the multilayer/bulk of MoS 2 shows an indirect band gap ($ 1.3 eV). 15 These properties make MoS 2 a promising material in future nanoscale electronic and optoelectronic device applications such as photocatalysis, 16 photodetectors, 17 biosensors, 18 gas sensors, 19 phototransistors, 20 field-effect transistors (FETs), 21 solar cells 22 and light-emitting diodes (LEDs).…”

Section: Introductionmentioning

confidence: 99%

MoS2 Thin Films Grown by Sulfurization of DC Sputtered Mo Thin Films on Si/SiO2 and C-Plane Sapphire Substrates

Akçay

Тиванов

Özçelik

2021

Journal of Elec Materi

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Here we report the growth of molybdenum disulfide (MoS 2) films with different thicknesses on silicon dioxide/silicon (SiO 2 /Si) and c-plane sapphire substrates by sulfurization of direct current (DC) sputtered Mo precursor films in a chemical vapor deposition furnace with sulfur powder at 900°C. The structural, morphological, optical, and electrical properties of the films on different substrates were investigated through a series of characterization in detail. X-ray diffraction (XRD) results showed that the grown films on sapphire substrates had better crystallization and a well-stacked layered structure than the films on SiO 2 /Si substrates. The frequency difference between the characteristic modes E 1 2g and A 1g of hexagonal phase MoS 2 was determined as $ 26 cm À1 which is consistent with the typical value of bulk MoS 2. Energy-dispersive x-ray (EDX) spectra exhibited that the films were near-stoichiometric. A small shift towards the lower binding energies in the Mo 3d 5/2 peak positions was observed due to the valency of Mo below +4 depending on the compositional ratios of the films in xray photoelectron spectroscopy (XPS) spectra. Atomic force microscopy (AFM) and scanning electron microscopy (SEM) analysis indicated that the films had smooth surfaces and a well-packed crystal structure. However, when the thickness of the films deposited on sapphire substrates increased, the strain between the sapphire substrate and MoS 2 film caused the formation of the micro-domes in the film. In addition, the films exhibited high absorption and reflection properties in the near-infrared (NIR) and mid-infrared (MIR) regions in Fourier transform infrared (FTIR) analysis. Therefore, it is considered that the films can be used for photodetector applications in these regions and infrared shielding coating applications.

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Temperature controlled 1T/2H phase ratio modulation in mono- and a few layered MoS2 films

Cited by 35 publications

References 41 publications

Effect of Deposition Pressure on the Microstructure and Optical Band Gap of Molybdenum Disulfide Films Prepared by Magnetron Sputtering

Effect of Deposition Pressure on the Microstructure and Optical Band Gap of Molybdenum Disulfide Films Prepared by Magnetron Sputtering

O Plasma Treatment Enhanced Room Temperature Ferromagnetism in MoS2

MoS2 Thin Films Grown by Sulfurization of DC Sputtered Mo Thin Films on Si/SiO2 and C-Plane Sapphire Substrates

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