Layer dependent thermal transport properties of one- to three-layer magnetic Fe:MoS2

Elham Easy; Mengqi Fang; Mingxing Li; Eui-Hyeok Yang; Xian Zhang

doi:10.1038/s41598-024-84524-8

. 2025 Jan 2;15:127. doi: 10.1038/s41598-024-84524-8

Layer dependent thermal transport properties of one- to three-layer magnetic Fe:MoS₂

Elham Easy ¹, Mengqi Fang ¹, Mingxing Li ², Eui-Hyeok Yang ¹, Xian Zhang ^1,^✉

PMCID: PMC11697255 PMID: 39747637

Abstract

Two-Dimensional transition metal dichalcogenides have been the subject of extensive attention thanks to their unique properties and atomically thin structure. Because of its unprecedented room-temperature magnetic properties, iron-doped MoS₂ (Fe:MoS₂) is considered the next-generation quantum and magnetic material. It is essential to understand Fe:MoS₂’s thermal behavior since temperature and thermal load/activation are crucial for their magnetic properties and the current nano and quantum devices have been severely limited by thermal management. In this work, Fe:MoS₂ is synthesized by doping Fe atoms into MoS₂ using the chemical vapor deposition synthesis and a refined version of opto-thermal Raman technique is used to study the thermal transport properties of Fe:MoS₂ in the forms of single (1L), bilayer (2L), and tri-layer (3L). In the Opto-thermal Raman technique, a laser is focused on the center of a thin film and used to measure the peak position of a Raman-active mode. The lateral thermal conductivity of 1-3L of Fe:MoS₂ and the interfacial thermal conductance between Fe:MoS₂ and the substrate were obtained by analyzing the temperature-dependent and power-dependent Raman measurement, laser power absorption coefficient, and laser spot sizes. At the room temperature, the lateral thermal conductivity of 1-3L Fe:MoS₂ were discovered as 24 ± 11, 18 ± 9, and 16 ± 8 W/m·K, respectively which presents a decreasing trend from 1 to 3L and is about 40% lower than that of MoS₂. The interfacial thermal conductance of between Fe:MoS₂ and the substrate were discovered to be 0.3 ± 0.2, 1.1 ± 0.7, and 3.0 ± 2.3 MW/m²⋅K for 1L to 3L respectively. We also characterized Fe:MoS₂’s thermal transport at high temperature, and calculated Fe:MoS₂’s thermal transport by density theory function. These findings will shed light on the thermal management and thermoelectric designs for Fe:MoS₂ based nano and quantum electronic devices.

Subject terms: Materials science, Nanoscience and technology

Introduction

Two-dimensional (2D) materials and their unique properties have attracted significant attention in recent years. With the discovery of graphene¹, transition metal dichalcogenides (TMDCs)^2,3 have been researched extensively due to their interesting thermal^4–8, electrical⁹, thermoelectric¹⁰, and optical^11,12 properties. Among them, MoS₂ is a layered semiconductor composed of covalently bonded transition-metal atoms (Mo) and chalcogen atoms (S)¹³ with important applications in optoelectronic¹⁴ and nano-electronic devices¹⁵. The thermal transport properties of 2D MoS₂ are very different from the bulk. Due to higher efficiency, thin layer MoS₂ are promising electronic devices¹⁶. Impurities, such as vacancies, chemical doping, and grain boundaries, can lead to phonon scattering^17–20 and, as a result, thermal conductivity reduction. Green’s function suggests the higher likeliness of short wavelength or high-frequency phonon modes scattering by defects. Jenisha et al.¹⁴ revealed the reduction of thermal conductivity for Ni-doped MoS₂. They observed two times smaller thermal conductivity of about 0.48 W/m⋅K for 7.5% of Ni-doped MoS₂ than undoped MoS₂. Mao et al.¹⁵ reported a significant increase in electric conductivity and reduction in thermal conductivity for 1–10% vanadium atoms doped in MoS₂ lattice structure. Also, the thermal conductivity was significantly reduced due to point defects and interface scattering. Structural, optical, electrical, and phonon properties of V-doped and Ti-doped 2D MoS₂ were studied by Williamson et al.²¹ They revealed the concentration of 2.083% Ti is the most effective due to effective dopant isolation. The research indicated that Ti dopant impacts the phonon properties greater than V-doped; however, V-dopant has a great phonon anharmonicity due to shorter bond length and weaker covalent bonds.

Modifying the magnetic properties of MoS₂ nanosheets is crucial for expanding their applications in nanoelectronics²² and spintronics²³ using the diluted magnetic semiconductor (DMS) concept. MoS₂ nanosheets, however, are intrinsically nonmagnetic. Therefore, it is highly desirable to realize stable magnetism in MoS₂. Iron-doped Molybdenum disulfide (Fe:MoS₂) is considered a quantum material thanks to its intriguing properties, such as magnetic properties, lower mobility, more lattice impurities, and imperfections. Iron (Fe) doping into MoS₂ lattice structure has been reported to facilitate DMS formation²⁴, with Scanning Transmission Electron Microscopy (STEM), X-ray Photoelectron Spectroscopy (XPS), and Magnetic circular Dchroism (MCD) Spectroscopy characterizations of the Fe doping. The magnetic and electronic properties of Fe-doping monolayer MoS₂ have been studied using a combination of density functional theory by Shu et al.²⁵ They reported that the stability of Fe dopant in MoS₂ lattice structure depends on the layer number and chemical potential. In another work, Mishra et al.²⁶ investigated the electronic and magnetic properties of the Fe atom doped on the MoS₂ and MoS₂ using first-principal function theory. They reported that the dopant significantly changes magnetic moments, magnetic anisotropic energy, and charge transfer which counts as electronic properties. Wang et al.¹¹ compared undoped and Fe-doped MoS₂ chemical vapor deposition (CVD) grown optical and electrical properties. They observed longer carrier lifetime and lower mobility for Fe:MoS₂ compared to MoS₂. Despite all the studies on Fe:MoS₂, the thermal transport properties of Fe:MoS₂ has not been extensively investigated. The findings could be used to design Fe doped MoS₂ electronic devices in the future.

In this work, we report the in-plane thermal conductivity of 1L, 2L, and 3L Fe:MoS₂ and the interfacial thermal conductance between the Fe:MoS₂ and SiO₂ substrate for the first time. The opto-thermal Raman technique is employed to measure the thermal properties^27,28 of Fe:MoS₂. This technique is contactless, with no fabrication requirement and capable of directly measuring thermal conductivity without changing the physical properties of pristine samples. It is particularly ideal for measuring 2D materials due to their sub-nanometer thickness. The result has been confirmed by the computational method, density theory function.

Results

MoS₂ monolayers were synthesized via Low pressure chemical vapor deposition (LPCVD). The schematic of growth using the chemical vapor deposition is shown in Fig. 1, and the details are described in the Methods section.

Fig. 1 — Schematic of chemical vapor deposition (CVD) growth process for Fe:MoS₂.

The morphology of the Fe:MoS₂ samples was characterized by optical microscopy and scanning electron microscopy as shown in Figs. 2a and b, respectively. To confirm the growth of 1-3L Fe:MoS₂ domains, the sample is characterized by the atomic force microscopy (AFM) peak force mode (Bruker Dimension) as shown in Fig. 2c. The thicknesses of 1L, 2L, and 3L Fe:MoS₂ are 0.8 nm, 1.6 nm, and 2.4 nm. The AFM image also confirms that there is no Fe₃O₄ residual remaining on the surface of Fe:MoS₂ after wet cleaning and thermal annealing. Figure 2d is the top view schematic of crystal structure of Fe:MoS₂.

Raman and photoluminescence (PL) spectroscopy provide evidence that Fe is incorporated into the lattice (Fig. 2). To demonstrate the success of doping MoS₂ with Fe, the photoluminescence (PL) spectra of the 1L MoS₂ and Fe:MoS₂ were characterized under a 405 nm laser excitation with 5 mW power at 300 K. There are two broad bands in the PL spectrum associated with two excitons peaks formed by spin–orbit coupling in the valence band (direct excitonic transition). The left PL peak at 1.86 eV represents MoS₂ and the right peak at 1.49 eV represents Fe in Fe:MoS₂. The red-shift of 0.37 eV caused by defect in MoS₂ lattice structure. Figure 2e shows that the PL intensity of the Fe:MoS₂ sample dropped significantly compared to the MoS₂ sample. This optical quenching results from the MoS₂ lattice distortion due to the introducing of the Fe dopants into the lattice and the existence of additional nonradiative channels known as trap states^11,29.

Due to the highly mobile charges and wide access to shallow trap states, MoS₂ is expected to have more electron concentration when Fe dopants are introduced. Fe is an n-type dopant, so Fe-doping is expected to increase electron concentrations in Fe:MoS₂ monolayers. Due to the reduction in neutral excitons and the increase in negative trion emission, the peak position of the PL would be redshifted, as previous studies demonstrated³⁰. The spectra of 1L MoS₂ and 1L Fe:MoS₂ samples were collected using a micro-Raman spectrometer (Renishaw InVia Raman Microscope system) under 514 nm laser excitation. Both spectra demonstrate the in-plane E¹_2g and out-of-plane A_1g vibration modes of MoS₂ as shown in Fig. 2f. The E¹_2g and A_1g models of the pristine MoS₂ sample are at 385.4 cm⁻¹ and 404.6 cm⁻¹, respectively. The A_1g model of the Fe:MoS₂ is at 404.2 cm⁻¹, which is like that of the pristine MoS₂. However, the E¹_2g model of the Fe:MoS₂ is at 381.1 cm⁻¹, indicating a red shift as compared with that of the MoS₂. The observed red-shift can be related to the defect in MoS₂ lattice structure¹⁶. In addition, Raman spectroscopy was employed to further confirm that Fe incorporates into the MoS₂ lattice. Figure 2g presents a comparison of PL emission for MoS₂ and Fe:MoS₂. It is clear from this figure that the Fe-related emission at 2.28 eV can only be observed from 1L Fe:MoS₂¹⁶, which also validates the substitution of Mo by Fe atoms and there is no peak at 2.28 eV for 1L MoS₂. This peak is only observable for 1L Fe:MoS₂ at room temperature since 2.28 eV peak is considered as PL emission and is affected by band gap. The band gap changes from direct to indirect as the layer number increases from monolayer to thicker samples. Therefore, the quench for the 2.28 eV peak disappears for samples thicker than 1L³¹.

Figure 3a presents a schematic of the experimental setup for the Fe:MoS₂ sample by the opto-thermal Raman technique, while in Fig. 3b a schematic of the Raman laser and thermal transport profiles can be observed. At temperatures ranging from 303 to 423 K, we calibrated the Raman E¹_2g peak position shift rate. A laser with a wavelength λ of 514 nm was used. A Raman spectrum of 1L Fe:MoS₂ with temperature dependence is shown in Fig. 3c.

To acquire Inline graphic (power-dependent coefficient), the E¹_2g mode shift of the Fe:MoS₂ samples was also measured using the micro-Raman system under the 514 nm laser excitation. Then the power dependent coefficient can be derived from the equation of , where is the Raman peak frequency at absorbed laser power P, Inline graphic is the Raman peak frequency at power 0 and P is the absorbed laser power. The absorbed laser power can be calculated by multiplying the incident laser power with the absorbance (α) of the samples. The confocal absorption spectra were recorded with a Nikon Eclipse TE2 equipped with an Acton 500 spectrograph and a PIXIS 100 CCD camera (NT&C Consulting, Germany). Figure 4a shows the absorbance of the 1L, 2L, and 3L Fe:MoS₂ as a function of wavelength. We used the interpolated method to extract the absorbance at 514 nm wavelength. The absorbance values of 1L, 2L, and 3L Fe:MoS₂ are 0.0127, 0.0344, and 0.0831, respectively. 1L-3L Fe:MoS₂ were prepared on a transparent quartz substrate, and the transmittance T of 1L-3L Fe:MoS₂ at the wavelength of 480 nm – 800 nm were characterized. The absorbance A were calculated as Inline graphic . The E¹_2g peak position as a function of the absorbed laser power was characterized using both 100 and 50 objective lens of the Raman system as shown in Fig. 4b, c, and d. The laser light acted as both the thermometer and the heat source for the Fe:MoS₂ flakes. It can be observed that the E¹_2g peak of all the samples decreases almost linearly as a function of the absorbed laser power. This is because the local temperature rise induced by the laser heating resulted in red shift due to the phonon softening effect. The convection through the air is negligible since it is less than 0.01% for all the measured samples¹⁸. Both Inline graphic and are extracted via linear regression and summarized in Table 1.

Fig. 4 — (a) Absorbance of 1-3L Fe:MoS₂ at wavelengths from 480 to 800 nm. (b) Power-dependent E_2g¹ Raman peak shift characterized using two different laser spot sizes, on the 1L Fe:MoS₂, (c) 2L Fe:MoS₂, and (d) 3L Fe:MoS₂.

Table 1.

First-order temperature coefficients, absorbance, and power shift rates of 1–3L Fe:MoS₂.

	Temperature coefficient (cm⁻¹/K)	Absorbance (%)	Absorbed power shift rate (cm⁻¹/µw)
	Temperature coefficient (cm⁻¹/K)	Absorbance (%)	0.18 µm spot size	0.31 µm spot size
1L Fe:MoS₂	−0.0176 ± 0.0020	1.27	−0.1185 ± 0.0036	−0.0644 ± 0.00150
2L Fe:MoS₂	−0.0143 ± 0.0008	3.44	−0.0383 ± 0.0009	−0.0182 ± 0.00004
3L Fe:MoS₂	−0.0131 ± 0.0008	8.31	−0.0158 ± 0.0004	−0.0067 ± 0.00004

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To calculate the thermal conductivity, one also need to know the laser spot size of the Raman system. The laser spot size of both 100 Inline graphic and 50 objective lenses was measured using the knife-edge method³². In this method, the laser moves across a sharp edge and using the Raman mapping feature the Si peak is monitored. The Si peak intensity as a function of position had been studied with Gaussian distribution as mentioned in equation below

where r₀ is the laser spot size, x_c is the center of peak position, and I₀ is the initial intensity. The laser spot size passing through 100× and 50× was 0.18 µm and 0.31 µm, respectively. The measurements were made in the air at ambient temperature. Laser spot size can also be estimated from the numerical aperture. Inline graphic where λ is the laser wavelength and NA is the numerical aperture. For 100× and 50×, the calculated result using the numerical aperture is 0.19 µm and 0.22 µm, respectively. The substrate interaction can make the mean free paths of phonons in Fe:MoS₂ smaller than the laser beam size, especially for long-wavelength phonons³³. In the cylindrical coordinate T(r), the temperature distribution is related to the in-plane thermal conductivity, interfacial thermal conductance between the flake and substrate, and the absorbed laser power. The volumetric laser heating power density q^’’’(r) based on the Gaussian profile of the laser equation below is

where P is the absorbed laser power, t is the thickness of the flake, and r₀ is the laser spot size. After taking the interfacial thermal conductance between the flake and the substrate into consideration, T(r) is presented by the equation below

where g is the interfacial thermal conductance between the flake and the substrate, K_s is the in-plane thermal conductivity of Fe:MoS₂ and T_a is the ambient temperature. The weighted result can be calculated by considering the Gaussian profile of the laser spot. The equation below is the average temperature.

To solve the equations, boundary conditions need to be defined. Based on the Gaussian profile of the laser Inline graphic , the maximum temperature is in the center where the laser shines on the sample ( and further away from the center, the temperature is the ambient temperature . We also need to calculate the thermal resistance of Fe:MoS_2, which can be calculated as and relate the thermal resistance to the thermal conductivity and the interfacial thermal conductance between the flake and the substrate. The ratio of two R_m characterized from two laser spot sizes is a function of g/K_s. The calculated results are K_s = 24 ± 11 W/m⋅K, and g = 0.3 ± 0.2 MW/m²⋅K for 1L Fe:MoS₂, K_s = 18 ± 9 W/m⋅K, and g = 1.1 ± 0.7 MW/m²⋅K for 2L Fe:MoS₂, and K_s = 16 ± 8 W/m⋅K, and g = 3.0 ± 2.3 MW/m²⋅K for 3L Fe:MoS₂.

To obtain the relationship between Raman peak shift and temperature rise, we also heated the samples from room temperature to 500 K on the heating platform. The optothermal Raman characterizations were conducted with a Raman laser of low power (100 μW). The thermal conductivity and interfacial thermal conductance between the flake and substrate are summarized in Table 2.

Table 2.

Thermal conductivities of 1–3L Fe:MoS₂ at room temperature (300 K) and at 500 K, and their interfacial thermal conductance.

	Thermal conductivity (W/m⋅K)		Interfacial thermal conductance (MW/m²⋅K)
	At 300 K	At 500 K	Interfacial thermal conductance (MW/m²⋅K)
1L Fe:MoS₂	24 ± 11	19 ± 10	0.3 ± 0.2
2L Fe:MoS₂	18 ± 9	11 ± 6	1.1 ± 0.7
3L Fe:MoS₂	16 ± 8	8 ± 3	3.0 ± 2.3

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Discussion

Thermal conductivities of 1-3L Fe:MoS₂ have been explored and found in the range of 16–24 W/m⋅K which is about 40% lower than the reported values for MoS₂¹⁸. This value is also smaller than other TMDC materials, such as MoS₂, MoSe₂, and WSe₂, due to the imperfect lattice structure of MoS₂ from the doping engineering. The iron doped MoS₂ causes imperfection in the lattice structure, leading to phonon scattering and a further reduction in thermal conductivity. The phonon scattering rate caused by imperfections can be derived from Green’s function approach or calculated using Fermi’s golden rule^34,35. The phonon scattering rate for 2D materials can be estimated by the formula Inline graphic , where m and r_a are the average atom mass and radius, is the phonon group velocity, is the Gruneisen parameter, mi, ra, i, and fi are the mass, radius, and fraction concentration of type i atom, and is a parameter for defect scattering due to lattice distortion and mass difference. This expression indicates the likelihood of high-frequency phonon modes scattering by defects. Since the Fe atoms substitute the Mo atoms in MoS₂ lattice structure, the difference between the atomic radius and the atomic mass of these two materials cause a change in phonon scattering rate³⁶.

A decreasing trend of thermal conductivities and an increasing trend in interfacial thermal conductance have been observed with increasing layer numbers of Fe:MoS₂. The decreasing trend of thermal conductivities from thinner layer to thicker layer is due to the stronger phonon-boundary scattering. The strength of boundary condition scattering, which is defined as Inline graphic where t is the thickness, decreases in the layered 2D crystals due to the weak van der Waals interaction ³⁶. In addition, the decreasing trend is associated with the Umkkalpp phonon scattering, crystal’s phonon anharmonicity, and reduction of ballistic resistance that affects phonon mean free path for thicker flakes. Other studies on the MoS₂, MoSe₂, WSe₂, and hBN also faced the decreasing trend of thermal conductivity with increasing the number of layers^18,37,38. The increasing trend in interfacial thermal conductance could be explained that as the number of layers increases, the interface between 2D materials and the substrate becomes more tightly coupled. In addition, there are less defects in 2D materials with increased layers because more layers can act as “bridge” between 2D materials and the substrate. We also compared to the undoped CVD MoS₂ that we synthesized with the Fe doped CVD MoS₂ in this work(with Fe concentration 0.3–0.5%), and found the Fe doped CVD MoS₂’s thermal conductivity is ~ 30% smaller. This decrease in thermal conductivity is due to the defects in the material created during the doping process.

Computational studies were carried out in parallel to verify the experimental results. we utilized a combination of phonopy, thirdorder, and ShengBTE software, integrated with VASP first-principles DFT calculations, to compute the thermal conductivity of Fe-doped MoS₂. The second- and third-order interatomic force constants were extracted and employed to solve the phonon Boltzmann transport equation. For this, we constructed a 4 × 4 × 1 supercell of monolayer MoS₂, with one Mo atom substituted by an Fe atom to introduce doping. Following structural optimization, the atomic configuration corresponding to the minimum energy was identified. The cutoff energy for plane-wave basis sets was set to 400 eV, ensuring sufficient accuracy, while the energy convergence criterion was set to 1 × 10⁻⁶ eV, which provided precise structural optimization. Additionally, we used a Γ-centered k-point mesh of 6 × 6 × 1 for Brillouin zone sampling and employed a Methfessel-Paxton smearing method with a width of 0.05 eV to ensure electronic structure convergence during the relaxation process. the cutoff distance was set to 0.3 Å in the calculation of third-order force constants for neighboring atoms. We employed a 10 × 10 × 10 q-grid to more accurately estimate phonon frequencies and phonon lifetimes, ensuring better resolution of the phonon characteristics for our calculations.

The thermal conductivity results revealed that for the monolayer Fe-doped MoS₂, the in-plane thermal conductivity was 28.3 W/mK. In contrast, for the bilayer Fe-doped MoS₂, the in-plane thermal conductivity dropped to 20.3 W/mK. The in-plane thermal conductivity of the 3L material is 18.8 W/mK. The computational results are in good agreement with the experimental findings. These findings indicate that the significant reduction in thermal conductivity for multilayered 2D materials, as compared to their monolayer counterparts, can be attributed to the poor efficiency of interlayer thermal transport. The out-of-plane thermal conductivity remains several orders of magnitude lower than the in-plane thermal conductivity, which is primarily responsible for the observed suppression of thermal transport in the multilayer structure.

Methods

MoS₂ monolayers were synthesized via Low pressure chemical vapor deposition (LPCVD). Before growth, a thin MoO₃ layer was prepared using physical vapor deposition (PVD) of e-beam evaporating MoO₃ pellet onto a Si substrate with 300 nm-thick thermal oxides. Subsequently, the MoO₃-deposited substrate was in direct contact with a different SiO₂/Si substrate. On the SiO₂/Si substrate, monolayers of Fe:MoS₂ were grown. The following steps were taken to dope the Fe atoms: the MoO₃-deposited substrate was rinsed with deionized (DI) water to deposit a thin layer of water on the SiO₂ surface to ensure that the Fe₃O₄ particles were distributed uniformly. Fe₃O₄ particles were uniformly cast onto the SiO₂/Si substrate and then the substrate was baked at 110 °C for 5 min. During the growth, the furnace was heated with a ramping rate of 18 ˚C/min and held for 15 min at 850 ˚C. Upon the heating procedure, an argon gas (30 sccm) was supplied at 300 ˚C, and a hydrogen gas (15 sccm) was delivered at 760 ˚C. Sulfur was supplied when the furnace temperature reached 790 ˚C. After the growth, a few millimeters of Fe:MoS₂ monolayers were obtained.

Conclusion

It is the first work to explore the thermal transport properties of the novel magnetic 2D material Fe:MoS₂ in its 1L to 3L forms, both experimentally and computationally. Fe:MoS₂ is produced via the LPCVD method, with Fe atoms in the lattice structure of Fe:MoS₂ characterized by Raman spectroscopy and photoluminescence. Our refined opto-thermal Raman method was used to characterize the in-plane thermal conductivity and interfacial thermal conductance of Fe:MoS₂. A decreasing trend has been observed for thermal conductivities of Fe:MoS₂ as the layer number increases. The in-plane thermal conductivities of 1L, 2L, and 3L Fe:MoS₂ are 24 ± 11 W/m⋅K, 18 ± 9 W/m⋅K, and 16 ± 8 W/m⋅K and the interfacial thermal conductivity are 0.3 ± 0.2 MW/m²⋅K, 1.1 ± 0.7 MW/m²⋅K, and 3.0 ± 2.3 MW/m²⋅K respectively. These values will help us to understand their thermal behavior, the critical factor that has a significant limitation on nano- and quantum devices. Experimental results show a layer-dependent trend of thermal conductivity.

Acknowledgements

This work was supported by the National Science Foundation CAREER Award (Grant CBET-2145417) and LEAPS Award (Grant DMR-2137883).

Author contributions

X.Z. contributed to the conceptualization and the methodology. E.E. and X.Z. contributed to the investigation. M.F. and E.Y. contributed to the material synthesis. M.L. contributed to the optical characterization. E.Y. contributed to writing the original draft. X.Z. contributed to writing the review and editing. All authors have given approval to the final version of the manuscript.

Funding

National Science Foundation CAREER Award (Grant CBET-2145417) and LEAPS Award (Grant DMR-2137883).

Data availability

The datasets used and analysed during the current study available from the corresponding author on reasonable request.

Declarations

Competing interests

The authors declare no conflict of interest.

Footnotes

Publisher's note

Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

References

1.Novoselov, K. S. et al. Electric field effect in atomically thin carbon films. Science306(5696), 666–669 (2004). [DOI] [PubMed] [Google Scholar]
2.Amani, M. et al. Recombination kinetics and effects of superacid treatment in sulfur- and selenium-based transition metal dichalcogenides. Nano Lett.16(4), 2786–2791 (2016). [DOI] [PubMed] [Google Scholar]
3.Ahmed, S. & Yi, J. Two-dimensional transition metal dichalcogenides and their charge carrier mobilities in field-effect transistors. Nano-Micro Lett.9(4), 50 (2017). [DOI] [PMC free article] [PubMed] [Google Scholar]
4.Kandemir, A., Yapicioglu, H., Kinaci, A., Çağın, T. & Sevik, C. Thermal transport properties of MoS2 and MoSe2 monolayers. Nanotechnology27(5), 055703 (2016). [DOI] [PubMed] [Google Scholar]
5.Wang, Y. & Zhang, X. Thermal transport in graphene under large mechanical strains. J. Appl. Phys.136(7), 074302 (2024). [Google Scholar]
6.Ye, F., Liu, Q., Xu, B., Feng, P. X. L. & Zhang, X. Ultra-high interfacial thermal conductance via double hBN encapsulation for efficient thermal management of 2D electronics. Small19(12), 2205726 (2023). [DOI] [PubMed] [Google Scholar]
7.Kalantari, M. H., Zhang, X. Thermal transport in 2D materials. Nanomaterials [Online] (2023). [DOI] [PMC free article] [PubMed]
8.Wang, Y. & Zhang, X. On the role of crystal defects on the lattice thermal conductivity of monolayer WSe2 (P63/mmc) thermoelectric materials by DFT calculation. Superlattices Microstruct.160, 107057 (2021). [Google Scholar]
9.Seyler, K. L. et al. Electrical control of second-harmonic generation in a WSe2 monolayer transistor. Nature Nanotechnol.10(5), 407–411 (2015). [DOI] [PubMed] [Google Scholar]
10.Babaei, H., Khodadadi, J. M. & Sinha, S. Large theoretical thermoelectric power factor of suspended single-layer MoS2. Appl. Phys. Lett.105(19), 193901 (2014). [Google Scholar]
11.Wang, S. Y., Ko, T. S., Huang, C. C., Lin, D. Y. & Huang, Y. S. Optical and electrical properties of MoS2 and Fe-doped MoS2. Japanese J. Appl. Phys.53(4S), 04EH07 (2014). [Google Scholar]
12.Wang, Y., Zhang, X. Experimental and theoretical investigations of direct and indirect band gaps of WSe2 Micromachines [Online] (2024). [DOI] [PMC free article] [PubMed]
13.Mas-Ballesté, R., Gómez-Navarro, C., Gómez-Herrero, J. & Zamora, F. 2D materials: To graphene and beyond. Nanoscale3(1), 20–30 (2011). [DOI] [PubMed] [Google Scholar]
14.Jenisha, M. A. et al. Interfacial engineering effect and bipolar conduction of Ni- doped MoS2 nanostructures for thermoelectric application. J. Alloys Compd.895, 162493 (2022). [Google Scholar]
15.Mao, Y., Fang, Y., Yuan, K. & Huang, F. Effect of vanadium doping on the thermoelectric properties of MoS2. J. Alloys Compd.903, 163921 (2022). [Google Scholar]
16.Chen, Y. et al. Tuning electronic structure of single layer MoS2 through defect and interface engineering. ACS Nano12(3), 2569–2579 (2018). [DOI] [PubMed] [Google Scholar]
17.Zhou, W.-X. et al. Thermal conductivity of amorphous materials. Adv. Funct. Mater.30(8), 1903829 (2020). [Google Scholar]
18.Chen, X.-K., Zhang, E.-M., Wu, D. & Chen, K.-Q. Strain-induced medium-temperature thermoelectric performance of Cu₄TiSe₄: The role of four-phonon scattering. Phys. Rev. Appl.19(4), 044052 (2023). [Google Scholar]
19.Chen, X.-K. et al. Large contributions from optical phonons to thermal transport in hexagonal carbon-boron-nitrogen monolayers. Phys Rev B108(23), 235420 (2023). [Google Scholar]
20.Kuang, H.-L., Wu, C.-W., Zeng, Y.-J., Chen, X.-K. & Zhou, W.-X. The amplification effect of four-phonon scattering in CdX (X=Se, Te): The role of mid-frequency phonons. Int. J. Thermal Sci.205, 109254 (2024). [Google Scholar]
21.Williamson, I. et al. Structural, electrical, phonon, and optical properties of Ti- and V-doped two-dimensional MoS2. Chem. Phys. Lett.674, 157–163 (2017). [Google Scholar]
22.Yokoo, A. Nanoelectrode lithography. Jpn. J. Appl. Phys.42(2A), L92 (2003). [Google Scholar]
23.Zibouche, N., Kuc, A., Musfeldt, J. & Heine, T. Transition-metal dichalcogenides for spintronic applications. Ann. der Phys.526(9–10), 395–401 (2014). [Google Scholar]
24.Fu, S. et al. Enabling room temperature ferromagnetism in monolayer MoS2 via in situ iron-doping. Nature Commun.11(1), 2034 (2020). [DOI] [PMC free article] [PubMed] [Google Scholar]
25.Shu, H., Luo, P., Liang, P., Cao, D. & Chen, X. Layer-dependent dopant stability and magnetic exchange coupling of iron-doped MoS2 nanosheets. ACS Appl. Mater. Interfaces7(14), 7534–7541 (2015). [DOI] [PubMed] [Google Scholar]
26.Mishra, N., Pandey, B. P. & Kumar, S. Impact of Mn- and Fe-doping on electronic and magnetic properties of MoX₂ (X = S, Se) monolayer. IEEE Trans. Electron Devices69(3), 1553–1560 (2022). [Google Scholar]
27.Zhang, X. et al. Measurement of lateral and interfacial thermal conductivity of single- and bilayer MoS2 and MoSe2 using refined optothermal Raman technique. ACS Appl. Mater. Interfaces7(46), 25923–25929 (2015). [DOI] [PubMed] [Google Scholar]
28.Easy, E. et al. Experimental and computational investigation of layer-dependent thermal conductivities and interfacial thermal conductance of one- to three-layer WSe2. ACS Appl. Mater. Interfaces13(11), 13063–13071 (2021). [DOI] [PubMed] [Google Scholar]
29.Zhang, S. et al. Controllable, wide-ranging n-doping and p-doping of monolayer group 6 transition-metal disulfides and diselenides. Adv. Mater.30(50), 1806345 (2018). [DOI] [PubMed] [Google Scholar]
30.Mouri, S., Miyauchi, Y. & Matsuda, K. Tunable photoluminescence of monolayer MoS2 via chemical doping. Nano Lett.13(12), 5944–5948 (2013). [DOI] [PubMed] [Google Scholar]
31.Zhang, K. et al. Tuning the electronic and photonic properties of monolayer MoS2 via in situ rhenium substitutional doping. Adv. Funct. Mater.28(16), 1706950 (2018). [Google Scholar]
32.Suzaki, Y. & Tachibana, A. Measurement of the μm sized radius of Gaussian laser beam using the scanning knife-edge. Appl. Opt.14(12), 2809–2810 (1975). [DOI] [PubMed] [Google Scholar]
33.Xiaokun Gu, R. Y. Phonon transport and thermal conductivity in two-dimensional materials. In: Annual Review of Heat Transfer, Begell: 2016.
34.Klemens, P. G., The scattering of low-frequency lattice waves by static imperfections. Proceedings of the Physical Society. Section A1955,68 (12), 1113.
35.Klemens, P. G. Theory of the a-plane thermal conductivity of graphite. J. Wide Bandgap Mater.7, 332–339 (2000). [Google Scholar]
36.Yarali, M. et al. Effects of defects on the temperature-dependent thermal conductivity of suspended monolayer molybdenum disulfide grown by chemical vapor deposition. Adv. Funct. Mater.27(46), 1704357 (2017). [Google Scholar]
37.Cai, Q., Scullion, D., Gan, W., Falin, A., Zhang, S., Watanabe, K., Taniguchi, T., Chen, Y., Santos, E. J. G., Li, L. H. High thermal conductivity of high-quality monolayer boron nitride and its thermal expansion. Sci. Adv. 5(6), eaav0129. [DOI] [PMC free article] [PubMed]
38.Yuan, P., Wang, R., Wang, T., Wang, X., Xie, Y. Nonmonotonic thickness-dependence of in-plane thermal conductivity of few-layered MoS2: 2.4 to 37.8 nm. Phys. Chem. Chem. Phys. 2018, 20(40), 25752–25761. [DOI] [PubMed]

Associated Data

This section collects any data citations, data availability statements, or supplementary materials included in this article.

Data Availability Statement

The datasets used and analysed during the current study available from the corresponding author on reasonable request.

[CR1] 1.Novoselov, K. S. et al. Electric field effect in atomically thin carbon films. Science306(5696), 666–669 (2004). [DOI] [PubMed] [Google Scholar]

[CR2] 2.Amani, M. et al. Recombination kinetics and effects of superacid treatment in sulfur- and selenium-based transition metal dichalcogenides. Nano Lett.16(4), 2786–2791 (2016). [DOI] [PubMed] [Google Scholar]

[CR3] 3.Ahmed, S. & Yi, J. Two-dimensional transition metal dichalcogenides and their charge carrier mobilities in field-effect transistors. Nano-Micro Lett.9(4), 50 (2017). [DOI] [PMC free article] [PubMed] [Google Scholar]

[CR4] 4.Kandemir, A., Yapicioglu, H., Kinaci, A., Çağın, T. & Sevik, C. Thermal transport properties of MoS2 and MoSe2 monolayers. Nanotechnology27(5), 055703 (2016). [DOI] [PubMed] [Google Scholar]

[CR5] 5.Wang, Y. & Zhang, X. Thermal transport in graphene under large mechanical strains. J. Appl. Phys.136(7), 074302 (2024). [Google Scholar]

[CR6] 6.Ye, F., Liu, Q., Xu, B., Feng, P. X. L. & Zhang, X. Ultra-high interfacial thermal conductance via double hBN encapsulation for efficient thermal management of 2D electronics. Small19(12), 2205726 (2023). [DOI] [PubMed] [Google Scholar]

[CR7] 7.Kalantari, M. H., Zhang, X. Thermal transport in 2D materials. Nanomaterials [Online] (2023). [DOI] [PMC free article] [PubMed]

[CR8] 8.Wang, Y. & Zhang, X. On the role of crystal defects on the lattice thermal conductivity of monolayer WSe2 (P63/mmc) thermoelectric materials by DFT calculation. Superlattices Microstruct.160, 107057 (2021). [Google Scholar]

[CR9] 9.Seyler, K. L. et al. Electrical control of second-harmonic generation in a WSe2 monolayer transistor. Nature Nanotechnol.10(5), 407–411 (2015). [DOI] [PubMed] [Google Scholar]

[CR10] 10.Babaei, H., Khodadadi, J. M. & Sinha, S. Large theoretical thermoelectric power factor of suspended single-layer MoS2. Appl. Phys. Lett.105(19), 193901 (2014). [Google Scholar]

[CR11] 11.Wang, S. Y., Ko, T. S., Huang, C. C., Lin, D. Y. & Huang, Y. S. Optical and electrical properties of MoS2 and Fe-doped MoS2. Japanese J. Appl. Phys.53(4S), 04EH07 (2014). [Google Scholar]

[CR12] 12.Wang, Y., Zhang, X. Experimental and theoretical investigations of direct and indirect band gaps of WSe2 Micromachines [Online] (2024). [DOI] [PMC free article] [PubMed]

[CR13] 13.Mas-Ballesté, R., Gómez-Navarro, C., Gómez-Herrero, J. & Zamora, F. 2D materials: To graphene and beyond. Nanoscale3(1), 20–30 (2011). [DOI] [PubMed] [Google Scholar]

[CR14] 14.Jenisha, M. A. et al. Interfacial engineering effect and bipolar conduction of Ni- doped MoS2 nanostructures for thermoelectric application. J. Alloys Compd.895, 162493 (2022). [Google Scholar]

[CR15] 15.Mao, Y., Fang, Y., Yuan, K. & Huang, F. Effect of vanadium doping on the thermoelectric properties of MoS2. J. Alloys Compd.903, 163921 (2022). [Google Scholar]

[CR16] 16.Chen, Y. et al. Tuning electronic structure of single layer MoS2 through defect and interface engineering. ACS Nano12(3), 2569–2579 (2018). [DOI] [PubMed] [Google Scholar]

[CR17] 17.Zhou, W.-X. et al. Thermal conductivity of amorphous materials. Adv. Funct. Mater.30(8), 1903829 (2020). [Google Scholar]

[CR18] 18.Chen, X.-K., Zhang, E.-M., Wu, D. & Chen, K.-Q. Strain-induced medium-temperature thermoelectric performance of Cu₄TiSe₄: The role of four-phonon scattering. Phys. Rev. Appl.19(4), 044052 (2023). [Google Scholar]

[CR19] 19.Chen, X.-K. et al. Large contributions from optical phonons to thermal transport in hexagonal carbon-boron-nitrogen monolayers. Phys Rev B108(23), 235420 (2023). [Google Scholar]

[CR20] 20.Kuang, H.-L., Wu, C.-W., Zeng, Y.-J., Chen, X.-K. & Zhou, W.-X. The amplification effect of four-phonon scattering in CdX (X=Se, Te): The role of mid-frequency phonons. Int. J. Thermal Sci.205, 109254 (2024). [Google Scholar]

[CR21] 21.Williamson, I. et al. Structural, electrical, phonon, and optical properties of Ti- and V-doped two-dimensional MoS2. Chem. Phys. Lett.674, 157–163 (2017). [Google Scholar]

[CR22] 22.Yokoo, A. Nanoelectrode lithography. Jpn. J. Appl. Phys.42(2A), L92 (2003). [Google Scholar]

[CR23] 23.Zibouche, N., Kuc, A., Musfeldt, J. & Heine, T. Transition-metal dichalcogenides for spintronic applications. Ann. der Phys.526(9–10), 395–401 (2014). [Google Scholar]

[CR24] 24.Fu, S. et al. Enabling room temperature ferromagnetism in monolayer MoS2 via in situ iron-doping. Nature Commun.11(1), 2034 (2020). [DOI] [PMC free article] [PubMed] [Google Scholar]

[CR25] 25.Shu, H., Luo, P., Liang, P., Cao, D. & Chen, X. Layer-dependent dopant stability and magnetic exchange coupling of iron-doped MoS2 nanosheets. ACS Appl. Mater. Interfaces7(14), 7534–7541 (2015). [DOI] [PubMed] [Google Scholar]

[CR26] 26.Mishra, N., Pandey, B. P. & Kumar, S. Impact of Mn- and Fe-doping on electronic and magnetic properties of MoX₂ (X = S, Se) monolayer. IEEE Trans. Electron Devices69(3), 1553–1560 (2022). [Google Scholar]

[CR27] 27.Zhang, X. et al. Measurement of lateral and interfacial thermal conductivity of single- and bilayer MoS2 and MoSe2 using refined optothermal Raman technique. ACS Appl. Mater. Interfaces7(46), 25923–25929 (2015). [DOI] [PubMed] [Google Scholar]

[CR28] 28.Easy, E. et al. Experimental and computational investigation of layer-dependent thermal conductivities and interfacial thermal conductance of one- to three-layer WSe2. ACS Appl. Mater. Interfaces13(11), 13063–13071 (2021). [DOI] [PubMed] [Google Scholar]

[CR29] 29.Zhang, S. et al. Controllable, wide-ranging n-doping and p-doping of monolayer group 6 transition-metal disulfides and diselenides. Adv. Mater.30(50), 1806345 (2018). [DOI] [PubMed] [Google Scholar]

[CR30] 30.Mouri, S., Miyauchi, Y. & Matsuda, K. Tunable photoluminescence of monolayer MoS2 via chemical doping. Nano Lett.13(12), 5944–5948 (2013). [DOI] [PubMed] [Google Scholar]

[CR31] 31.Zhang, K. et al. Tuning the electronic and photonic properties of monolayer MoS2 via in situ rhenium substitutional doping. Adv. Funct. Mater.28(16), 1706950 (2018). [Google Scholar]

[CR32] 32.Suzaki, Y. & Tachibana, A. Measurement of the μm sized radius of Gaussian laser beam using the scanning knife-edge. Appl. Opt.14(12), 2809–2810 (1975). [DOI] [PubMed] [Google Scholar]

[CR33] 33.Xiaokun Gu, R. Y. Phonon transport and thermal conductivity in two-dimensional materials. In: Annual Review of Heat Transfer, Begell: 2016.

[CR34] 34.Klemens, P. G., The scattering of low-frequency lattice waves by static imperfections. Proceedings of the Physical Society. Section A1955,68 (12), 1113.

[CR35] 35.Klemens, P. G. Theory of the a-plane thermal conductivity of graphite. J. Wide Bandgap Mater.7, 332–339 (2000). [Google Scholar]

[CR36] 36.Yarali, M. et al. Effects of defects on the temperature-dependent thermal conductivity of suspended monolayer molybdenum disulfide grown by chemical vapor deposition. Adv. Funct. Mater.27(46), 1704357 (2017). [Google Scholar]

[CR37] 37.Cai, Q., Scullion, D., Gan, W., Falin, A., Zhang, S., Watanabe, K., Taniguchi, T., Chen, Y., Santos, E. J. G., Li, L. H. High thermal conductivity of high-quality monolayer boron nitride and its thermal expansion. Sci. Adv. 5(6), eaav0129. [DOI] [PMC free article] [PubMed]

[CR38] 38.Yuan, P., Wang, R., Wang, T., Wang, X., Xie, Y. Nonmonotonic thickness-dependence of in-plane thermal conductivity of few-layered MoS2: 2.4 to 37.8 nm. Phys. Chem. Chem. Phys. 2018, 20(40), 25752–25761. [DOI] [PubMed]

PERMALINK

Layer dependent thermal transport properties of one- to three-layer magnetic Fe:MoS₂

Elham Easy

Mengqi Fang

Mingxing Li

Eui-Hyeok Yang

Xian Zhang

Abstract

Introduction

Results

Fig. 1.

Fig. 2.

Fig. 3.