Solution-Based Synthesis of Oxide-Free MoS2 Film: Exploring Interface Mechanisms

doi:10.21203/rs.3.rs-4320986/v1

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Solution-Based Synthesis of Oxide-Free MoS2 Film: Exploring Interface Mechanisms

https://doi.org/10.21203/rs.3.rs-4320986/v1

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We report a solution-based approach for the synthesis of oxidation-free MoS₂ films, focusing on interface mechanisms. Through a sulfurization-free solution process and single-step annealing, the oxidation-free MoS₂ film is successfully prepared on Si₃N₄ surfaces, showing improved uniformity with a surface roughness below 0.5 nm and a thickness of 4 nm at a precursor solution concentration of 30 mM, annealed between 700 and 800ºC. The MoS₂ films exhibit a hexagonal lattice structure with crystallographic orientations of (1 1 0 0) and (1 2 1 0) with lattice spacings of 0.27 nm and 0.16 nm respectively. Interfacial analysis by X-ray photoelectron spectroscopy (XPS) on SiO₂ reveals migration of oxygen species as evidenced by a shift in the Si 2p spectrum at binding energies between 102.6eV and 102.8eV. MoS₂ films on Si₃N₄ show a complex Si 2p peak evolution at binding energies between 100.9 and 101.8 eV, providing valuable insights into the synthesis of oxide-free MoS₂ films for potential applications in advanced electronic devices.

Physical sciences/Engineering

Physical sciences/Materials science

Physical sciences/Physics

Transitional metal dichalcogenides

MoS2

oxide-free surface

thermal desorption spectroscopy

interface mechanisms

Extensive research has focused on layered two-dimensional (2D) materials, with particular emphasis on 2D molybdenum disulfide (MoS₂) due to its atomically thin nature,^1,2 mechanical flexibility,³ sizeable bandgaps (1.2-1.9eV),^4,5 high carrier mobility (517 cm²V^− 1s),⁶ high on/off current ratio(10⁹),⁷ and excellent thermal switching behavior.⁸ These properties have made MoS₂ a promising candidate to replace and outperform existing material technologies in FET channels and electronic device applications.^9–11 However, maintaining these superior properties faces challenges such as unstable interfaces and the presence of native oxides,¹² leading to performance degradation¹³ and defects.¹⁴ Therefore, understanding interface mechanisms and selecting suitable dielectric surfaces is crucial to overcoming these challenges. While SiO₂ surfaces affect both long-range and short-range scattering parameters, leading to disruptions in FET performance,^15,16 oxide-free dielectrics like Si₃N₄ have been proposed to effectively address these limitations.¹⁷ Single-layer MoS₂ on a SiO₂ dielectric surface transferred by mechanical exfoliation shows a decrease in mobility.^18,19 Chemical vapor deposition (CVD)^20–22 through sulfurization is an excellent method for high-quality MoS₂ films, but it is expensive and environmentally harmful and poses challenges for large-scale production and lateral film uniformity.²³ Comparable limitations are encountered with the chemical exfoliation method.²⁴

The sol-gel method via spin-coating followed by annealing is popular because of its time and cost efficiency.^25,26 Yang et al. achieved uniform MoS₂ films through a two-step annealing process with an additional sulfur source.²⁷ Bhattacharya et al. employed a plasma-assisted chemical conversion method without sulfurization, using a vacuum chamber for moisture elimination.²⁸ Meanwhile, Can et al. utilized Electrohydrodynamic (EHD) jet printing instead of spin coating for MoS₂ film synthesis²⁹ which presents challenges for microscale formation. Each method has its advantages and drawbacks in terms of simplicity, time, and potential side effects in the production of MoS₂ films. However, none have addressed the oxidation-free state and detailed interface mechanism of MoS₂ films on an oxide-free dielectric surface.

In our study, we present a sulfurization-free synthesis of MoS₂ films on both SiO₂ and Si₃N₄ surfaces. This method employs a solution-based spin-coating technique followed by a single-step annealing process at temperatures ranging from 500°C to 1000°C. The synthesis begins with a solution consisting of dimethylformamide (DMF), ammonium thiomolybdate (ATM), supplemented with isopropanol (IPA), and ethanolamine. The MoS₂ films exhibit superior uniformity on Si₃N₄ surfaces, with reduced roughness below 0.5 nm and a thickness of 4 nm when annealed between 700°C and 800°C. Importantly, Si₃N₄ surfaces yield oxide-free MoS₂ films, making them highly suitable for applications in FET channels. This approach circumvents the challenges associated with sulfurization and process complexity and offers a promising route to the cost-effective and efficient production of high-quality MoS₂ films.

The MoS₂ film synthesis process starts with substrate preparation and cleaning. Silicon substrates with a thermally grown (O₂:3slm, H₂:3slm, and 1000℃) SiO₂ layer (290 nm) and a low-pressure chemical vapor deposition (LPCVD) grown (NH₃:110sccm, SiH₂Cl₂:10sccm, and 120mTorr) Si₃N₄ layer (80 nm) were used in this process. The substrates were cleaned with acetone, IPA, and DI water, and then treated with UV/O₃. Although all processes were carried out in a controlled cleanroom environment, Si₃N₄ surfaces were subjected to 0.5% HF treatment, followed by 15 minutes of pre-annealing with Ar gas to prevent oxidation prior to spin coating. A precursor solution with a concentration of 30mM was prepared by dissolving ammonium tetrathiomolybdate [(NH₄)₂MoS₄] (Sigma Aldrich, purity 99.999%) powder in a solution of dimethylformamide (DMF), IPA, and ethanolamine in a ratio of 3:5:3 (v/v). After continuous stirring for 2h, the precursor solution was then spin-coated onto the clean SiO₂ and Si₃N₄ surfaces at a rotation speed of 500 rpm for 10s and 3000 rpm for 30s respectively. The spin-coated films were converted into MoS₂ films by a pre-annealing step at 180°C for 30 minutes in a cleanroom environment, followed by a single-step annealing process performed in a lamp annealing system(ADVANCE RIKO, Inc.). The annealing temperatures range between 500°C to 1000°C for 1 hour with an Ar gas flow rate of 1 slm. Figure 1 provides a comprehensive overview of the synthesis process flow and annealing procedure while the purpose of utilizing each solvent has been illustrated in supplementary information (ST1).

Various materials analysis techniques were used to examine the converted thin films to assess their exact stoichiometry, identify any residual precursor in trace amounts, and determine the oxidation state of the film. Atomic Force Microscopy was executed employing a Bruker-Dimension icon featuring ScanAsyst. Raman spectroscopy was carried out at ambient temperature using a Horiba XploRA PLUS which incorporates a confocal Raman microscope system equipped with a thermoelectric-cooled CCD camera. The laser's excitation wavelength was 532 nm, and the laser beam was focused through a 100× objective lens to achieve a spot size of approximately 1µm, facilitated by a 2400 groove/mm grating. X-ray diffraction analysis was conducted utilizing a Rigaku SmartLab 9kW Series diffractometer equipped with a Cu-Kα radiation source. X-ray photoelectron spectroscopy (XPS) was performed with a PHI VersaProbe 4 using an Al-Kα radiation source.

The demonstrated relationship between MoS₂ and the surface morphology of the substrate reveals that the regular performance may be affected by the presence of metal oxide dielectrics.¹⁶ To realize better surface morphology, we synthesized MoS₂ films on both SiO₂ and Si₃N₄ surfaces. Optical microscopy was employed initially to observe as-synthesized and converted MoS₂ films (shown in Fig. 2a). Figure 2(b) illustrates the AFM images of annealed (converted) MoS₂ films fabricated on both SiO₂ (upper panel) and Si₃N₄ (lower panel) surfaces at annealing temperatures ranging from 600°C-1000°C. At different annealing temperatures, SiO₂ surfaces show the appearance of numerous grains (shown in Fig. 2c) with a height between 2 and 8.5 nm. Intriguingly, these grains are nearly absent on Si₃N₄ surfaces up to an annealing temperature of 800°C as illustrated in Fig. 2(d). This indicates superior uniformity and crystallinity in MoS₂ films compared to SiO₂ surfaces. During the annealing process, Si or oxygen may migrate from SiO₂ to the MoS₂ interface with lower sulfur content, leading to grain formation. This migration process will be discussed in a later section focusing on the interface analysis of MoS₂ films grown on both surfaces.

At annealing temperatures exceeding 800°C (SiO₂) and 900°C (Si₃N₄), we observe larger grains with significant boundaries on both surfaces. We suggest that these grains may correspond to either Mo or MoO_x, depending on the specific surface. The AFM and X-ray reflectivity (XRR) techniques were employed to estimate the roughness and thickness of the MoS₂ films, respectively. High-quality MoS₂ film formation typically begins above 600°C during annealing,³⁰ thus we skipped AFM analysis for the film formed at 500°C. Figure 2(e) and (f) illustrate the roughness (R_a) and thickness as a function of annealing temperatures. The R_a values of the MoS₂ films on Si₃N₄ surfaces are found to be below 0.5 nm with a thickness of ~ 4 nm (between 600°C and 800°C), indicating a smoother surface compared to films formed on SiO₂ surfaces using a similar technique, as reported previously.³¹ As the annealing temperatures rise from 800°C, the R_a values for both surfaces show an increase. This can be attributed to less sulfur content in MoS₂ films at high annealing temperatures, leaving only metal or metal oxide on the surface. The film thickness on SiO₂ surfaces varies as the height of remaining structures fluctuates with increasing annealing temperatures. The thickness, however, depends on the spin coating and concentration of the precursor solution.

Due to the improved surface morphology observed in our synthesized MoS₂ films on Si₃N₄ compared to the SiO₂ surface, we intend to concentrate on analyzing Si₃N₄ surfaces for the subsequent stages of our analysis. Raman spectroscopy was next employed to examine the converted MoS₂ films. Figure 3 displays Raman intensity (a.u) plotted against Raman shift (cm ^− 1) at different annealing temperatures. A mechanically exfoliated MoS₂ crystal is used as a reference to assess the distinctive Raman peaks of films produced at annealing temperatures ranging from 500°C to 1000°C. Two characteristic Raman active modes emerge: the out-of-plane vibration of S atoms (A_1g), exhibiting a Raman shift around ∼406 cm^− 1, and the in-plane vibration involving Mo and S atoms (E_2g) at approximately ∼382 cm^− 1 during annealing temperatures ranging from 700°C to 800°C. This closely corresponds to our reference MoS₂ crystal(A_1g = 407 cm^− 1 and E_2g = 383 cm^− 1) and aligns with the previous report.^32,33 The characteristics A_1g and E_2g peaks with a difference of 24 cm^− 1, suggests the formation of semiconducting 2H- multilayer MoS₂ films³⁴ within the similar temperature range. This matches well with our estimated thickness as determined by XRR.

On the other hand, the emergence of A_1g and E_2g peaks at lower annealing temperatures (< 700°C) shows a minimal presence or reduced intensity, suggesting the absence of MoS₂ film formation. Additionally, we also assume the absence of MoS₂ film on both surfaces at higher annealing temperatures, starting from 900°C.

X-ray diffraction (XRD) was employed to analyze the crystalline phase and orientation of MoS₂ films. In Fig. 4(a), XRD patterns are depicted for MoS₂ crystals and MoS₂ films on the Si₃N₄ surface, after annealing from 500°C to 1000°C. The exfoliated MoS₂ crystal displays diffraction peaks at 2θ_𝝌/𝞅 angles of 32.7°, 47.5°, and 58.4°, corresponding to (1 1 0 0), (2 2 0), and (1 2 1 0) orientations. Converted MoS₂ films show similar peaks at temperatures between 700°C to 800°C, maintaining identical orientations. The (1 1 0 0) and (1 2 1 0) orientations are attributed to MoS₂ films with a hexagonal lattice structure, while (2 2 0) corresponds to Si, consistent with previous XRD results.³⁵ At temperatures above 800°C, additional patterns appear, along with an extra peak at 40.3° (1 1 0), indicating MoS₂ or Mo and a combination of these (Supplementary Figure S1), attributed to large grains confirmed by AFM topology (Fig. 2b). However, MoS₂ films on SiO₂ surfaces show a similar orientation (Fig. 4b), with an expanded peak around 20.4°, likely assigned to the SiO₂ surface during annealing.^36,37

In addition, we determined the Full Width at Half Maximum (FWHM) based on the area of XRD patterns of MoS₂(1 1 0 0), MoS₂(1 2 1 0), and Si(2 2 0) orientations taking MoS₂ crystals as a reference and the plots are illustrated in Fig. 4(c). The MoS₂ films on Si₃N₄ show a decreasing FWHM with higher annealing temperatures, similar trends to those observed in the fabrication of ALD-assisted MoO₃ film.³⁸ This suggests an improvement in the crystal quality of the films. Notably, this improvement remains consistent for Mo and Si respectively. We then used Fusion360 to illustrate the crystal structure and lattice spacings (Fig. 4d) of our MoS₂ film based on the crystallographic orientations obtained from the XRD patterns. In Fig. 4(e), a top view of the MoS₂ crystal shows lattice spacings of 0.27nm and 0.16nm, corresponding well to the MoS₂(1 1 0 0) and MoS₂(1 2 1 0) planes. These results are in good agreement with a previous study by Heeseung Yang et. al.³¹

The above results and discussion highlight that MoS₂ exhibits superior surface morphology in terms of uniformity, roughness, and crystallinity on Si₃N₄ compared to SiO₂, as confirmed through AFM, Raman spectroscopy, and XRD analysis. These improvements are attributed to specific annealing temperatures in the range of 700°C to 800°C.

The annealed MoS₂ thin film was analyzed by X-ray photoelectron spectroscopy (XPS) to accurately determine its stoichiometry, detect any residual precursor elements, and evaluate the oxidation state induced by either moisture or the annealing process. Figure 5 shows the core level XPS analysis of the Mo 3d, S 2p, and O 1s for both surfaces. Gaussian-Lorentzian fitting was used to identify individual components. On the SiO₂ surface, Mo 3d peaks appear at 227.6 and 230.8 eV, corresponding to Mo 3d_5/2 (cyan-blue line) and Mo 3d_3/2 (green line) doublets, respectively, as shown in Fig. 5a. In addition, a peak at 225.5 eV attributed to sulfur atoms, denoted as 2s (orange line), is evident. In contrast, XPS analysis of films on the Si₃N₄ surface shows Mo 3d peaks at 228.1 and 231.4 eV, with the S peak at 225.9 eV. We attribute these binding energy peaks to the Mo-S bond in MoS₂ films.³⁹ The discrepancy in binding energies between Si₃N₄ and SiO₂ surfaces may be due to surface oxidation of MoS₂ or migration of Si or oxygen from SiO₂ into the film. In order to accurately fit the Mo3d_5/2 and Mo3d_3/2 peaks, additional sets of low-intensity doublets were required to achieve a satisfactory fit. A peak corresponding to MoO₂ (blue line) at a binding energy of 228.3 eV for Mo3d_5/2, together with other peaks overlapping with Mo3d_3/2 at 232.1 and 233.3 eV, representing MoO₂ (dark cyan line) and MoO₃ (wine line) respectively. These oxides can be attributed to oxygen migration during annealing or to the uneven surface of SiO₂. Similarly, in addition to MoO₂ (Mo 3d_3/2), metal oxides at the binding energies of 229.2 eV and 232.8 eV are observed on the Si₃N₄ surface (Fig. 5d), possibly due to exposure to air or water, although the surface is initially free of oxide. These binding energies are in close agreement with those reported in the literature.^40,39

XPS analysis of MoS₂ films on Si₃N₄ reveals an oxidation-free surface compared to SiO₂, and our focus then shifts to the analysis of trace elements on the Si₃N₄ surface (Fig. 5e). The observed binding energies at 161.7 and 162.8 eV, in agreement with previous report,⁴¹ correspond to the S 2p_3/2 and S 2p_1/2 peaks of sulfur. A weaker peak at 163.9 eV indicates subsurface sulfur rather than residual surface contamination.^42,43 Similar sulfur peaks are observed in MoS₂ films on SiO₂ (Fig. 5b). Further investigation of the O1s core level is shown in Figs. 5c and 5f for both surfaces. The detection of oxygen as bound Mo-O at 529.35 eV suggests its possible origin from MoO₃,³⁹ which is clearly distinct from Si-O at 531.4 eV. Interestingly, these oxide species are not present in the film grown on Si₃N₄.

The MoS₂ films have an oxidation-free surface on Si₃N₄, as verified by XPS analysis. However, it is suggested that during the annealing process, MoS₂ layers are initially formed on the SiO₂ surface, resulting in the diffusion of oxygen from SiO₂ to MoS₂. This ultimately leads to the formation of metal oxides at the interface between MoS₂ and SiO₂. The migration model is then briefly discussed in the following sections.

Elemental migration to MoS₂, caused by substrates or surface adsorbates, can affect electronic devices⁴⁴ when used as a channel. However, the precise migration mechanism between 2D MoS₂ and dielectric surfaces remains incompletely understood. Figure 6(a) illustrates the migration model from SiO₂ to MoS₂ during annealing above 600°C. We propose that elevated annealing temperatures cause sulfur loss, leading to the migration of silicon or oxygen from SiO₂ to MoS₂ films. Initially, the migration tends to accumulate at the edges of the MoS₂, particularly in regions of lower sulfur content. This process leads to the formation of an S-O bond. While the 2D layered MoS₂ surface provides a dangling bond-free and inert interface, sulfur vacancies are expected to be the dominant defects with energy formation in the range of 1.3-1.5eV.^45,46 A study of MoS₂ film formation by sputtering shows initial Mo adlayer formation at the MoS₂/SiO₂ interface, with subsequent annealing leading to Mo layer diffusion into SiO₂, resulting in the formation of molybdenum silicon oxide (MoO_xSi_y) layers.⁴⁷ A similar layer may potentially be formed in our MoS₂ films on the SiO₂ surface.

To confirm the migration, thick MoS₂ films on a SiO₂ surface were subjected to core-level XPS analysis. Figure 6(b) shows the atomic concentration variations with Ar sputtering time, derived from the peak areas of Mo 3d, S 2p, Si 2p, N 1s, O 1s, and C 1s. The concentration of Mo and S decreases with sputtering time, while Si and O show an opposite trend after 180s. A slight shift of the Si 2p peaks (shown in Fig. 6c) to higher binding energies (102.6eV to 102.8eV) at 190s, corresponding to the charge effect associated with either SiO₂.^48,49 At the same time, the Mo 3d peaks (see supplementary information Figure S2 ) shift to lower binding energy, causing the disappearance of the S peak, suggesting the effect of Ar sputtering on MoS₂ films. This shift is attributed to either the charging effect or changes in the chemical states from the film surface to the interface.⁵⁰ We also performed thermal desorption spectroscopy (TDS) on MoS₂ films deposited on the SiO₂ surface using a quadrupole mass spectrometer (QMS). The TDS spectra (Fig. 6d) for mass-to-charge ratios of m/z = 32 and 64 show a sharp peak at a desorption temperature below 400°C, attributed to the desorption of organic matter. Since QMS selectively filters substances based on mass-to-charge ratio, both S and O₂ can be assigned to m/z = 32, which persists up to about 730°C. In addition to direct S desorption, we also observed the presence of the sulfur oxidation product, namely SO₂, expressed as m/z = 64 in Fig. 6(d), at the same desorption temperature as m/z = 32. It should be emphasized that m/z = 64 is referred to as SO₂ rather than S₂ and is in agreement with previous TDS investigations.⁵¹

The release of sulfur in the form of SO₂ suggests oxygen transfer from SiO₂ to Mo-S bonds in low sulfur MoS₂ films, rather than from any adsorbates. This implies that migration occurs predominantly in the region of lower Mo or S content, leading to Mo-O and S-O bond formation at higher annealing temperatures, consistent with our proposed migration model. Notably, the organic matter in the films originates from the precursor solution itself, as evidenced by the absence of monolayer MoS₂ degradation after environmental exposure.⁵² L.M. Farigliano et al. have theoretically documented similar desorption studies.⁵³ The formation of SO₂ appears to be related to two discrete intermediates: OSOMo and Mo-OSO structures. The former, formed by oxygen migration into Mo-S, undergoes desorption of SO₂ with an energy barrier of 1.49 eV. The latter is formed by oxygen insertion bound to adjacent Mo atoms and undergoes desorption of SO and SO₂ with energy barriers of 0.41 eV and 0.78 eV, respectively.

Additional desorbed species are then examined as shown in Figure S3. No detectable sulfur (S) or sulfur-related species were identified in the TDS spectrum at both lower and higher desorption temperatures. A broadened shoulder is evident at mass-to-charge ratios (m/z) of 17 and 18 in the temperature range of 100 to 200°C, indicating the desorption of H₂O, although a definitive judgment proves difficult. A sharp peak of higher intensity is seen at all m/z ratios between 300 and 350°C, indicating the desorption of organic matter. In addition, smaller peaks of lower intensity at 440°C for m/z 31 and above 550°C present challenges in making conclusive judgments.

To illustrate the migration process on the Si₃N₄ surface, we conducted a depth profile XPS analysis of MoS₂ films, as depicted in Fig. 7. The concentration of oxygen remains constant at below 5% ( above 60% for SiO₂ surface at a sputtering time of 360 s) throughout the sputtering time (Fig. 7a). Similar decreasing trends to the SiO₂ surface are observed for Mo 3d and S 2p. However, the Si content increased after 210 s of sputtering, and the N content increased after 270 s. In Fig. 7(b), the XPS spectra show a complex evolution in the line shape of the Si 2p peaks with sputtering time. The binding energies ranging from 100.9 to 101.8 eV correspond to the Si-N bond of Si₃N₄ (depicted by the black line). Nevertheless, a shift from a higher binding energy (101.9 eV) to a lower one (100.3 eV) indicates a Si-rich Si₃N₄ surface (depicted by the red line) due to the charge effect,⁵⁴ though this is not evident in the MoS₂ interface. We propose that this shift may lead to the formation of Si-N and Si-Si bonds on the Si₃N₄ surface, resulting in the enrichment of Si on the Si₃N₄ surface denoted as Si_xN_y(x > 3,y < 4) in Fig. 7(b).⁵⁵ The Si-enriched surface of Si₃N₄ may result from the annealing process of MoS₂ films or the unexpected adjustment in the gas ratio during the formation of Si₃N₄ using LPCVD.

The migration process of Si₃N₄ to the MoS₂ film encounters hurdles, which are mainly attributed to the increased oxidation resistance observed at higher temperatures.⁵⁶ According to XPS results on Si₃N₄ produced by LPCVD on Si, surface migration of Si₃N₄ is only possible to Si that has undergone an oxygen-assisted plasma treatment. This treatment tends to lead to partial substitution of N by oxygen, resulting in the formation of Si-O bonds.⁵⁷ However, it is important to note the possible presence of oxygen adsorbed from the environment (Fig. 5d), which manifests as MoO₂, an unstable oxide. The elimination of this oxide requires the maintenance of a high-quality vacuum or inert environment during the preparation and preservation of MoS₂ films. Apart from this consideration, it is possible to achieve an oxide-free surface for MoS₂ films on the Si₃N₄ surface within the annealing temperature range of 700 to 800°C. The existence of oxygen (O₂) or moisture (H₂O) on the surface or interface of 2D MoS₂ can deteriorate the field effect mobility and increase hysteresis when utilized as a channel in FETs. Additionally, oxygen impurities originating from the dielectric surface during the annealing process in the formation of MoS₂ films can create a complex layer, potentially disrupting the usual electrical performance.^58,59 Hence, achieving oxide-free semiconducting films is feasible by selecting an oxide-free dielectric, such as silicon nitride (Si₃N₄), as demonstrated in our study.

This achievement is significant as nitride-based dielectrics generally exhibit superior interfaces compared to oxide (SiO₂) dielectrics. Such improvement can significantly enhance the performance of gate dielectrics, allowing a reduction in the interfacial defect density near the substrate,⁶⁰ making them suitable for applications on a large scale to miniaturized electronics.

In brief, this study demonstrates the successful fabrication of highly uniform MoS₂ films with a precisely controlled thickness on oxide-free Si₃N₄ substrates through a one-step annealing process without sulfurization, as opposed to SiO₂ surfaces. The impact of annealing temperature on both surfaces was systematically investigated. MoS₂ films were effectively formed without any observable grains on Si₃N₄ at annealing temperatures ranging from 700 to 800°C, while lower temperatures (< 600°C) proved challenging for MoS₂ film formation, as confirmed by Raman spectroscopy. Additionally, MoS₂ films on SiO₂ surfaces exhibited metal oxides, potentially originating from SiO₂ diffusion, whereas Si₃N₄ surfaces remained oxide-free, making them promising for applications in advanced electronic and optoelectronic devices. Lastly, an interface analysis of MoS₂ films through x-ray photoelectron spectroscopy suggests the feasibility of forming oxide-free MoS₂ films on Si₃N₄ surfaces using the solution method, paving the way for the large-scale production of MoS₂ films.

Author Contribution

Md Iftekharul Alam was responsible for conceptualization, methodology, drafting of the original manuscript, visualization, as well as review, editing, physical characterization, preparing figures, and data analysis. Rikiya Sumichika conducted the physical characterization using AFM, XRD, XRR, and Raman spectroscopy. Junichi Tsuchimotoi carried out the XPS measurements and some related analyses. Tadahiro Komeda provided reference MoS2 crystals and shared scientific thoughts for this study. Akinobu Teramoto supervised the project, handled project administration, secured funding, and oversaw review and editing. All authors have read and agreed to the published version of the manuscript.

Data availability statements

All the raw data has been uploaded to Zenodo and is now available on this platform. You can access the raw data from the following link:

https://doi.org/10.5281/zenodo.11075678

Acknowledgments

This research was supported by the Ministry of Education, Culture, Sports, Science and Technology of Japan (MEXT) under the project JPJ011438 for the establishment of Next-generation Novel Integrated Circuit Centers(x-nics).

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No competing interests reported.

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Solution-Based Synthesis of Oxide-Free MoS2 Film: Exploring Interface Mechanisms

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