In situ visualized synthesis of two-dimensional MoS<sub>2</sub> with tunable metal-to-semiconductor transition

Sheng Guo; Tiefeng Yang; Manyan Xie; Ziyi Huang; Hanrong Xie; Miao Liu; Zitong Liu; Haoran Guo; Rui Rong; Chui Pian; Ziliang Fang; Zhen Wang; Heyuan Guan; Huihui Lu

doi:10.1088/1674-4926/26060017

J. Semicond. > Just Accepted

ARTICLES

In situ visualized synthesis of two-dimensional MoS₂ with tunable metal-to-semiconductor transition

Sheng Guo¹, Tiefeng Yang^1,, Manyan Xie¹, Ziyi Huang¹, Hanrong Xie¹, Miao Liu¹, Zitong Liu¹, Haoran Guo¹, Rui Rong¹, Chui Pian¹, Ziliang Fang¹, Zhen Wang^2,, Heyuan Guan^1, and Huihui Lu^{1, 3,}

+ Author Affiliations

1. Guangdong Provincial Key Laboratory of Optical Fiber Sensing and Communications, Jinan University, Guangzhou 510632, China
2. State Key Laboratory of Infrared Science and Technology, Shanghai Institute of Technical Physics, Chinese Academy of Sciences, Shanghai 200083, China
3. International Cooperation Joint Laboratory for Optoelectronic Hybrid Integrated Circuits, Jinan University, Guangzhou 510632, China

Author Bio:

Sheng Guo is a research student at Jinan University. His research interests focus on the chemical vapor deposition growth, sulfurization conversion, structural characterization, and optoelectronic properties of two-dimensional transition-metal dichalcogenides and related heterostructures.

Tiefeng Yang is an Associate Professor in the Department of Optoelectronic Engineering, Jinan University. His research interests focus on lithium-niobate/layered-semiconductor heterogeneous integration, two-dimensional optoelectronic devices, ferroelectric-related optoelectronic effects, and on-chip integrated photonic and electronic devices.

Zhen Wang is an Associate Researcher at the Shanghai Institute of Technical Physics, Chinese Academy of Sciences. His research interests focus on epitaxial growth of narrow-bandgap infrared semiconductors, emerging semiconductor optoelectronic devices, photoelectric modulation and detection mechanisms, and infrared optoelectronics.

Heyuan Guan is a Professor at the College of Physics and Optoelectronic Engineering, Jinan University, where he also serves as the Associate Dean of the college. His research focuses on micro-nano optoelectronic devices enhanced by thin film/grating structures, lithium niobate integrated devices, terahertz integrated devices, and optoelectronic integrated chips.

Huihui Lu is a Professor at the College of Physics and Optoelectronic Engineering, Jinan University, where he also serves as the Head of the Department of Optoelectronic Engineering. His research focuses on integrated optics, optical waveguide devices, micro/nano optoelectronic devices, and hybrid photonic integration.

Corresponding author: Tiefeng Yang, yangtiefeng2022@jnu.edu.cn; Zhen Wang, wangzhen@mail.sitp.ac.cn; Heyuan Guan, ttguanheyuan@jnu.edu.cn; Huihui Lu, thuihuilu@jnu.edu.cn

DOI: 10.1088/1674-4926/26060017CSTR: 32376.14.1674-4926.26060017

Abstract: Visualizing the growth of two-dimensional materials is crucial for clarifying growth mechanisms and enabling controllable synthesis. Recent in situ electron microscopy has captured atomic-scale images of MoS₂ growth, extending studies beyond post-growth characterization and theoretical simulations. Yet it remains unclear whether behavior observed under the demanding conditions of transmission electron microscopy and low vapor pressure applies to macroscopic vapor-phase synthesis. Here, we use in situ optical microscopy, Raman spectroscopy, electron microscopy, and device measurements to track the complete temperature-dependent conversion pathway of two-dimensional MoO₂ nanosheets into MoS₂ during sulfurization. The transformation is not a direct one-step phase transition. Rather, it follows a multistep pathway involving surface nucleation, formation of an amorphous Mo−S−O intermediate, local structural ordering, and final crystallization into layered MoS₂. Partially sulfurized samples retain structural asymmetry, including an intermediate phase, voids, strain, and moiré fringes, while fully sulfurized samples form uniform layered crystals. Device measurements show that this structural evolution is accompanied by a transport transition from metallic MoO₂ to semiconducting MoS₂. Moreover, exfoliated MoS₂ from partially sulfurized samples preserves local asymmetry and exhibits a pronounced pyroelectric effect under illumination, linking the conversion pathway with optoelectronic functionality.

Keywords: in-situ CVD, MoO₂/MoS₂ heterostructure, sulfurization, amorphous intermediate phase, metal-to-semiconductor phase evolution, 2D pyroelectrics

References

[1]	Zhu L Y, Yang Y, Dong X Q, et al. Radiation-tolerant atomic-layer-scale RF system for spaceborne communication. Nature, 2026, 650(8101): 346 doi: 10.1038/s41586-025-10027-9
[2]	Liu C S, Jiang Y B, Shen B Q, et al. A full-featured 2D flash chip enabled by system integration. Nature, 2025, 646(8087): 1081 doi: 10.1038/s41586-025-09621-8
[3]	Ao M R, Zhou X C, Kong X J, et al. A RISC-V 32-bit microprocessor based on two-dimensional semiconductors. Nature, 2025, 640(8059): 654 doi: 10.1038/s41586-025-08759-9
[4]	Xiang Y T, Wang C, Liu C S, et al. Subnanosecond flash memory enabled by 2D-enhanced hot-carrier injection. Nature, 2025, 641(8061): 90 doi: 10.1038/s41586-025-08839-w
[5]	Liu L, Wang Y S, Dong R K, et al. Kinetic acceleration of MoS₂ growth by oxy-metal-organic chemical vapor deposition. Science, 2026(6784): 494
[6]	Zou X L, Zhao Y Y, Fan D X, et al. Robust epitaxy of single-crystal transition-metal dichalcogenides on lanthanum-passivated sapphire. Science, 2025, 390(6771): eaea0849 doi: 10.1126/science.aea0849
[7]	Liu L, Li T T, Gong X S, et al. Homoepitaxial growth of large-area rhombohedral-stacked MoS₂. Nat Mater, 2025, 24(8): 1195 doi: 10.1038/s41563-025-02274-y
[8]	Liu L, Li T T, Ma L, et al. Uniform nucleation and epitaxy of bilayer molybdenum disulfide on sapphire. Nature, 2022, 605(7908): 69 doi: 10.1038/s41586-022-04523-5
[9]	Xu X L, Pan Y, Liu S, et al. Seeded 2D epitaxy of large-area single-crystal films of the van der Waals semiconductor 2H MoTe₂. Science, 2021, 372(6538): 195 doi: 10.1126/science.abf5825
[10]	Zhang Z W, Huang Z W, Li J, et al. Endoepitaxial growth of monolayer mosaic heterostructures. Nat Nanotechnol, 2022, 17(5): 493 doi: 10.1038/s41565-022-01106-3
[11]	Li T T, Guo W, Ma L, et al. Epitaxial growth of wafer-scale molybdenum disulfide semiconductor single crystals on sapphire. Nat Nanotechnol, 2021, 16(11): 1201 doi: 10.1038/s41565-021-00963-8
[12]	Zhou J D, Lin J H, Huang X W, et al. A library of atomically thin metal chalcogenides. Nature, 2018, 556(7701): 355 doi: 10.1038/s41586-018-0008-3
[13]	Zhang Z W, Chen P, Duan X D, et al. Robust epitaxial growth of two-dimensional heterostructures, multiheterostructures, and superlattices. Science, 2017, 357(6353): 788 doi: 10.1126/science.aan6814
[14]	Jiang H, Zhang X K, Chen K L, et al. Two-dimensional czochralski growth of single-crystal MoS₂. Nat Mater, 2025, 24(2): 188 doi: 10.1038/s41563-024-02069-7
[15]	Xu M Z, Ji H J, Zheng L, et al. Reconfiguring nucleation for CVD growth of twisted bilayer MoS₂ with a wide range of twist angles. Nat Commun, 2024, 15: 562 doi: 10.1038/s41467-023-44598-w
[16]	Liu C, Liu T Y, Zhang Z B, et al. Understanding epitaxial growth of two-dimensional materials and their homostructures. Nat Nanotechnol, 2024, 19(7): 907 doi: 10.1038/s41565-024-01704-3
[17]	Jeon S, Heo T, Hwang S Y, et al. Reversible disorder-order transitions in atomic crystal nucleation. Science, 2021, 371(6528): 498 doi: 10.1126/science.aaz7555
[18]	Li J J, Deepak F L. In situ kinetic observations on crystal nucleation and growth. Chem Rev, 2022, 122(23): 16911 doi: 10.1021/acs.chemrev.1c01067
[19]	Ye H Y, Wu C T, Cao D Y, et al. Atomically resolved two-dimensional amorphous nuclei formed during MoS₂ chemical vapor deposition. Science, 2026, 391(6785): 622 doi: 10.1126/science.adz8243
[20]	Jung Y, Ryu H, Kim H, et al. Nucleation and growth of monolayer MoS₂ at multisteps of MoO₂ crystals by sulfurization. ACS Nano, 2023, 17(8): 7865 doi: 10.1021/acsnano.3c01150
[21]	Zhu D C, Shu H B, Jiang F, et al. Capture the growth kinetics of CVD growth of two-dimensional MoS₂. npj 2D Mater Appl, 2017, 1: 8 doi: 10.1038/s41699-017-0010-x
[22]	Shaji A, Vegso K, Sojkova M, et al. Stepwise sulfurization of MoO₃ to MoS₂ thin films studied by real-time X-ray scattering. Appl Surf Sci, 2022, 606: 154772 doi: 10.1016/j.apsusc.2022.154772
[23]	Ponnusamy K M, Raveendran N, Durairaj S, et al. Spectroscopic visualization of intermediate phases during CVD synthesis of MoS₂. J Phys Chem Solids, 2023, 182: 111575 doi: 10.1016/j.jpcs.2023.111575
[24]	Luo L, Wu Y, Li L, et al. Symmetry-broken MoS₂ nanotubes through sequential sulfurization of MoO₂ nanowires. Nat Commun, 2025, 16: 8394 doi: 10.1038/s41467-025-63333-1
[25]	Chen Y Z, Lu C L, Wang F, et al. Phase transitions and controlled sulfurization of molybdenum oxides in vacuum. J Mater Sci, 2022, 57(35): 16569 doi: 10.1007/s10853-022-07669-9
[26]	Dahl-Petersen C, Šarić M, Brorson M, et al. Topotactic growth of edge-terminated MoS₂ from MoO₂ nanocrystals. ACS Nano, 2018, 12(6): 5351 doi: 10.1021/acsnano.8b00125
[27]	Qin B, Ma C J, Guo Q L, et al. Interfacial epitaxy of multilayer rhombohedral transition-metal dichalcogenide single crystals. Science, 2024, 385(6704): 99 doi: 10.1126/science.ado6038
[28]	Zhang Y C, Baek J H, Lee C H, et al. Atom-by-atom imaging of moiré transformations in 2D transition metal dichalcogenides. Sci Adv, 2024, 10(13): eadk1874 doi: 10.1126/sciadv.adk1874
[29]	Baek J H, Kim H G, Lim S Y, et al. Thermally induced atomic reconstruction into fully commensurate structures of transition metal dichalcogenide layers. Nat Mater, 2023, 22(12): 1463 doi: 10.1038/s41563-023-01690-2
[30]	Yang D Y, Wu J D, Zhou B T, et al. Spontaneous-polarization-induced photovoltaic effect in rhombohedrally stacked MoS₂. Nat Photonics, 2022, 16(6): 469 doi: 10.1038/s41566-022-01008-9
[31]	Li X Z, Qin B, Wang Y X, et al. Sliding ferroelectric memories and synapses based on rhombohedral-stacked bilayer MoS₂. Nat Commun, 2024, 15: 10921 doi: 10.1038/s41467-024-55333-4
[32]	Yang D Y, Liang J, Wu J D, et al. Non-volatile electrical polarization switching via domain wall release in 3R-MoS₂ bilayer. Nat Commun, 2024, 15: 1389 doi: 10.1038/s41467-024-45709-x
[33]	Wu W Z, Wang L, Li Y L, et al. Piezoelectricity of single-atomic-layer MoS₂ for energy conversion and piezotronics. Nature, 2014, 514(7523): 470 doi: 10.1038/nature13792
[34]	Deng L Y, Zhang Q, Li W Y, et al. KCl acts as a flux to assist the growth of sub-millimeter-scale metallic 2D non-layered molybdenum dioxide. Rare Met, 2025, 44(1): 404 doi: 10.1007/s12598-024-02898-0
[35]	Xie L B, Wang L L, Zhao W W, et al. WS₂ moiré superlattices derived from mechanical flexibility for hydrogen evolution reaction. Nat Commun, 2021, 12: 5070 doi: 10.1038/s41467-021-25381-1

Fig. 1. (Color online) Comparison between conventional studies and this work, temperature-dependent sulfurization behavior, and atomistic schematic of the sulfurization pathway. (a) Conventional studies generally infer the growth process from ex situ characterization of the final molybdenum disulfide (MoS₂) product. In this work, the sulfurization of molybdenum dioxide (MoO₂) nanosheets is monitored in real time using an in situ chemical vapor deposition (CVD) platform equipped with optical visualization. (b) Optical microscopy images acquired at different reaction times at 600 °C, showing the progressive conversion of a MoO₂ nanosheet. (c) Optical images acquired before and after sulfurization at 800 °C, showing epitaxial overgrowth and the formation of triangular nanosheets. (d) Optical images acquired before and after sulfurization at 950 °C, showing thermal decomposition of the sample.

DownLoad: Full-Size Img PowerPoint

Fig. 2. (Color online) Raman-spectroscopic characterization of the temperature-dependent MoO₂-to-MoS₂ sulfurization pathway. (a) Schematic of the sulfurization process: after edge- and surface-initiated conversion, a MoS₂ overlayer expands laterally across the MoO₂ nanosheet. (b−g) Raman spectra acquired from representative regions of samples sulfurized at 400, 500, 550, 600, 800 and 900 °C, respectively; the insets show the corresponding optical micrographs, with markers indicating the Raman acquisition positions.

DownLoad: Full-Size Img PowerPoint

Fig. 3. (Color online) Cross sectional structural and compositional analysis of the MoO₂-MoS₂ heterostructure in different regions of the same sample. (a) Cross sectional STEM image of the overall region. (b−c) Enlarged STEM images and corresponding EDS elemental maps of the marked regions in panel a: yellow boxed region (b, c), orange boxed region (d, e), and blue boxed region (f, g). (h) Elemental line scan profile across the region shown in panel f, the blue line indicates the scan path. (i) STEM image of another cross sectional region. (j) Statistical analysis of the Mo, O and S elemental contents in the regions marked in panels b and d.

DownLoad: Full-Size Img PowerPoint

Fig. 4. (Color online) Atomic scale structural characterization of partially sulfurized MoS₂/MoO₂ and fully sulfurized MoS₂, together with a schematic illustration of the sulfurization process. (a) Optical microscopy image of the partially sulfurized MoS₂/MoO₂ sample. (b) SAED pattern of the center region of the MoS₂/MoO₂ heterostructure, with the inset showing the corresponding TEM image. (c) Optical microscopy image of the fully sulfurized MoS₂ sample. (d) SAED pattern of the fully sulfurized MoS₂, with the inset showing the corresponding TEM image. (e) SAED pattern of the edge region of the MoS₂/MoO₂ heterostructure. (f) Corresponding TEM image. (g) Schematic illustration of MoS₂ moiré superlattices (MSLs). (h) Schematic illustration of the sulfurization conversion process from MoO₂ to MoS_2.

DownLoad: Full-Size Img PowerPoint

Fig. 5. (Color online) Device schematics, photoresponse and back gated field effect transistor characteristics of samples with different sulfurization degrees. (a, c, e) Transfer characteristics of the pristine MoO₂ device, the partially sulfurized MoO₂/MoS₂ heterostructure device, and the fully sulfurized MoS₂ device, respectively, the insets show the corresponding device schematics. (b, d, f) Corresponding I-V characteristics, with the insets showing the I-T characteristics. (g, h) I-T characteristics measured at 0 V under different illumination powers for the exfoliated MoS₂ from the partially sulfurized sample and the fully sulfurized MoS₂, respectively.

DownLoad: Full-Size Img PowerPoint

[1]	Zhu L Y, Yang Y, Dong X Q, et al. Radiation-tolerant atomic-layer-scale RF system for spaceborne communication. Nature, 2026, 650(8101): 346 doi: 10.1038/s41586-025-10027-9
[2]	Liu C S, Jiang Y B, Shen B Q, et al. A full-featured 2D flash chip enabled by system integration. Nature, 2025, 646(8087): 1081 doi: 10.1038/s41586-025-09621-8
[3]	Ao M R, Zhou X C, Kong X J, et al. A RISC-V 32-bit microprocessor based on two-dimensional semiconductors. Nature, 2025, 640(8059): 654 doi: 10.1038/s41586-025-08759-9
[4]	Xiang Y T, Wang C, Liu C S, et al. Subnanosecond flash memory enabled by 2D-enhanced hot-carrier injection. Nature, 2025, 641(8061): 90 doi: 10.1038/s41586-025-08839-w
[5]	Liu L, Wang Y S, Dong R K, et al. Kinetic acceleration of MoS₂ growth by oxy-metal-organic chemical vapor deposition. Science, 2026(6784): 494
[6]	Zou X L, Zhao Y Y, Fan D X, et al. Robust epitaxy of single-crystal transition-metal dichalcogenides on lanthanum-passivated sapphire. Science, 2025, 390(6771): eaea0849 doi: 10.1126/science.aea0849
[7]	Liu L, Li T T, Gong X S, et al. Homoepitaxial growth of large-area rhombohedral-stacked MoS₂. Nat Mater, 2025, 24(8): 1195 doi: 10.1038/s41563-025-02274-y
[8]	Liu L, Li T T, Ma L, et al. Uniform nucleation and epitaxy of bilayer molybdenum disulfide on sapphire. Nature, 2022, 605(7908): 69 doi: 10.1038/s41586-022-04523-5
[9]	Xu X L, Pan Y, Liu S, et al. Seeded 2D epitaxy of large-area single-crystal films of the van der Waals semiconductor 2H MoTe₂. Science, 2021, 372(6538): 195 doi: 10.1126/science.abf5825
[10]	Zhang Z W, Huang Z W, Li J, et al. Endoepitaxial growth of monolayer mosaic heterostructures. Nat Nanotechnol, 2022, 17(5): 493 doi: 10.1038/s41565-022-01106-3
[11]	Li T T, Guo W, Ma L, et al. Epitaxial growth of wafer-scale molybdenum disulfide semiconductor single crystals on sapphire. Nat Nanotechnol, 2021, 16(11): 1201 doi: 10.1038/s41565-021-00963-8
[12]	Zhou J D, Lin J H, Huang X W, et al. A library of atomically thin metal chalcogenides. Nature, 2018, 556(7701): 355 doi: 10.1038/s41586-018-0008-3
[13]	Zhang Z W, Chen P, Duan X D, et al. Robust epitaxial growth of two-dimensional heterostructures, multiheterostructures, and superlattices. Science, 2017, 357(6353): 788 doi: 10.1126/science.aan6814
[14]	Jiang H, Zhang X K, Chen K L, et al. Two-dimensional czochralski growth of single-crystal MoS₂. Nat Mater, 2025, 24(2): 188 doi: 10.1038/s41563-024-02069-7
[15]	Xu M Z, Ji H J, Zheng L, et al. Reconfiguring nucleation for CVD growth of twisted bilayer MoS₂ with a wide range of twist angles. Nat Commun, 2024, 15: 562 doi: 10.1038/s41467-023-44598-w
[16]	Liu C, Liu T Y, Zhang Z B, et al. Understanding epitaxial growth of two-dimensional materials and their homostructures. Nat Nanotechnol, 2024, 19(7): 907 doi: 10.1038/s41565-024-01704-3
[17]	Jeon S, Heo T, Hwang S Y, et al. Reversible disorder-order transitions in atomic crystal nucleation. Science, 2021, 371(6528): 498 doi: 10.1126/science.aaz7555
[18]	Li J J, Deepak F L. In situ kinetic observations on crystal nucleation and growth. Chem Rev, 2022, 122(23): 16911 doi: 10.1021/acs.chemrev.1c01067
[19]	Ye H Y, Wu C T, Cao D Y, et al. Atomically resolved two-dimensional amorphous nuclei formed during MoS₂ chemical vapor deposition. Science, 2026, 391(6785): 622 doi: 10.1126/science.adz8243
[20]	Jung Y, Ryu H, Kim H, et al. Nucleation and growth of monolayer MoS₂ at multisteps of MoO₂ crystals by sulfurization. ACS Nano, 2023, 17(8): 7865 doi: 10.1021/acsnano.3c01150
[21]	Zhu D C, Shu H B, Jiang F, et al. Capture the growth kinetics of CVD growth of two-dimensional MoS₂. npj 2D Mater Appl, 2017, 1: 8 doi: 10.1038/s41699-017-0010-x
[22]	Shaji A, Vegso K, Sojkova M, et al. Stepwise sulfurization of MoO₃ to MoS₂ thin films studied by real-time X-ray scattering. Appl Surf Sci, 2022, 606: 154772 doi: 10.1016/j.apsusc.2022.154772
[23]	Ponnusamy K M, Raveendran N, Durairaj S, et al. Spectroscopic visualization of intermediate phases during CVD synthesis of MoS₂. J Phys Chem Solids, 2023, 182: 111575 doi: 10.1016/j.jpcs.2023.111575
[24]	Luo L, Wu Y, Li L, et al. Symmetry-broken MoS₂ nanotubes through sequential sulfurization of MoO₂ nanowires. Nat Commun, 2025, 16: 8394 doi: 10.1038/s41467-025-63333-1
[25]	Chen Y Z, Lu C L, Wang F, et al. Phase transitions and controlled sulfurization of molybdenum oxides in vacuum. J Mater Sci, 2022, 57(35): 16569 doi: 10.1007/s10853-022-07669-9
[26]	Dahl-Petersen C, Šarić M, Brorson M, et al. Topotactic growth of edge-terminated MoS₂ from MoO₂ nanocrystals. ACS Nano, 2018, 12(6): 5351 doi: 10.1021/acsnano.8b00125
[27]	Qin B, Ma C J, Guo Q L, et al. Interfacial epitaxy of multilayer rhombohedral transition-metal dichalcogenide single crystals. Science, 2024, 385(6704): 99 doi: 10.1126/science.ado6038
[28]	Zhang Y C, Baek J H, Lee C H, et al. Atom-by-atom imaging of moiré transformations in 2D transition metal dichalcogenides. Sci Adv, 2024, 10(13): eadk1874 doi: 10.1126/sciadv.adk1874
[29]	Baek J H, Kim H G, Lim S Y, et al. Thermally induced atomic reconstruction into fully commensurate structures of transition metal dichalcogenide layers. Nat Mater, 2023, 22(12): 1463 doi: 10.1038/s41563-023-01690-2
[30]	Yang D Y, Wu J D, Zhou B T, et al. Spontaneous-polarization-induced photovoltaic effect in rhombohedrally stacked MoS₂. Nat Photonics, 2022, 16(6): 469 doi: 10.1038/s41566-022-01008-9
[31]	Li X Z, Qin B, Wang Y X, et al. Sliding ferroelectric memories and synapses based on rhombohedral-stacked bilayer MoS₂. Nat Commun, 2024, 15: 10921 doi: 10.1038/s41467-024-55333-4
[32]	Yang D Y, Liang J, Wu J D, et al. Non-volatile electrical polarization switching via domain wall release in 3R-MoS₂ bilayer. Nat Commun, 2024, 15: 1389 doi: 10.1038/s41467-024-45709-x
[33]	Wu W Z, Wang L, Li Y L, et al. Piezoelectricity of single-atomic-layer MoS₂ for energy conversion and piezotronics. Nature, 2014, 514(7523): 470 doi: 10.1038/nature13792
[34]	Deng L Y, Zhang Q, Li W Y, et al. KCl acts as a flux to assist the growth of sub-millimeter-scale metallic 2D non-layered molybdenum dioxide. Rare Met, 2025, 44(1): 404 doi: 10.1007/s12598-024-02898-0
[35]	Xie L B, Wang L L, Zhao W W, et al. WS₂ moiré superlattices derived from mechanical flexibility for hydrogen evolution reaction. Nat Commun, 2021, 12: 5070 doi: 10.1038/s41467-021-25381-1

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Received: 09 June 2026 Revised: 24 July 2026 Online: Accepted Manuscript: 13 August 2026

Article Navigation > Journal of Semiconductors > 2026 > Accepted Manuscript

Sheng Guo, Tiefeng Yang, Manyan Xie, Ziyi Huang, Hanrong Xie, Miao Liu, Zitong Liu, Haoran Guo, Rui Rong, Chui Pian, Ziliang Fang, Zhen Wang, Heyuan Guan, Huihui Lu. In situ visualized synthesis of two-dimensional MoS2 with tunable metal-to-semiconductor transition[J]. Journal of Semiconductors, 2026, In Press. doi: 10.1088/1674-4926/26060017 ****S Guo, T F Yang, M Y Xie, Z Y Huang, H R Xie, M Liu, Z T Liu, H R Guo, R Rong, C Pian, Z L Fang, Z Wang, H Y Guan, and H H Lu, In situ visualized synthesis of two-dimensional MoS2 with tunable metal-to-semiconductor transition[J]. J. Semicond., 2026, accepted doi: 10.1088/1674-4926/26060017

Citation:

S Guo, T F Yang, M Y Xie, Z Y Huang, H R Xie, M Liu, Z T Liu, H R Guo, R Rong, C Pian, Z L Fang, Z Wang, H Y Guan, and H H Lu, In situ visualized synthesis of two-dimensional MoS₂ with tunable metal-to-semiconductor transition[J]. J. Semicond., 2026, accepted doi: 10.1088/1674-4926/26060017

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In situ visualized synthesis of two-dimensional MoS₂ with tunable metal-to-semiconductor transition

DOI: 10.1088/1674-4926/26060017

CSTR: 32376.14.1674-4926.26060017

1.
Guangdong Provincial Key Laboratory of Optical Fiber Sensing and Communications, Jinan University, Guangzhou 510632, China
2.
State Key Laboratory of Infrared Science and Technology, Shanghai Institute of Technical Physics, Chinese Academy of Sciences, Shanghai 200083, China
3.
International Cooperation Joint Laboratory for Optoelectronic Hybrid Integrated Circuits, Jinan University, Guangzhou 510632, China

More Information

Sheng Guo is a research student at Jinan University. His research interests focus on the chemical vapor deposition growth, sulfurization conversion, structural characterization, and optoelectronic properties of two-dimensional transition-metal dichalcogenides and related heterostructures
Tiefeng Yang is an Associate Professor in the Department of Optoelectronic Engineering, Jinan University. His research interests focus on lithium-niobate/layered-semiconductor heterogeneous integration, two-dimensional optoelectronic devices, ferroelectric-related optoelectronic effects, and on-chip integrated photonic and electronic devices
Zhen Wang is an Associate Researcher at the Shanghai Institute of Technical Physics, Chinese Academy of Sciences. His research interests focus on epitaxial growth of narrow-bandgap infrared semiconductors, emerging semiconductor optoelectronic devices, photoelectric modulation and detection mechanisms, and infrared optoelectronics
Heyuan Guan is a Professor at the College of Physics and Optoelectronic Engineering, Jinan University, where he also serves as the Associate Dean of the college. His research focuses on micro-nano optoelectronic devices enhanced by thin film/grating structures, lithium niobate integrated devices, terahertz integrated devices, and optoelectronic integrated chips
Huihui Lu is a Professor at the College of Physics and Optoelectronic Engineering, Jinan University, where he also serves as the Head of the Department of Optoelectronic Engineering. His research focuses on integrated optics, optical waveguide devices, micro/nano optoelectronic devices, and hybrid photonic integration
Corresponding author: yangtiefeng2022@jnu.edu.cn; wangzhen@mail.sitp.ac.cn; ttguanheyuan@jnu.edu.cn; thuihuilu@jnu.edu.cn
Received Date: 2026-06-09
Revised Date: 2026-07-24

Available Online: 2026-08-13

Abstract

Abstract

Visualizing the growth of two-dimensional materials is crucial for clarifying growth mechanisms and enabling controllable synthesis. Recent in situ electron microscopy has captured atomic-scale images of MoS₂ growth, extending studies beyond post-growth characterization and theoretical simulations. Yet it remains unclear whether behavior observed under the demanding conditions of transmission electron microscopy and low vapor pressure applies to macroscopic vapor-phase synthesis. Here, we use in situ optical microscopy, Raman spectroscopy, electron microscopy, and device measurements to track the complete temperature-dependent conversion pathway of two-dimensional MoO₂ nanosheets into MoS₂ during sulfurization. The transformation is not a direct one-step phase transition. Rather, it follows a multistep pathway involving surface nucleation, formation of an amorphous Mo−S−O intermediate, local structural ordering, and final crystallization into layered MoS₂. Partially sulfurized samples retain structural asymmetry, including an intermediate phase, voids, strain, and moiré fringes, while fully sulfurized samples form uniform layered crystals. Device measurements show that this structural evolution is accompanied by a transport transition from metallic MoO₂ to semiconducting MoS₂. Moreover, exfoliated MoS₂ from partially sulfurized samples preserves local asymmetry and exhibits a pronounced pyroelectric effect under illumination, linking the conversion pathway with optoelectronic functionality.
- in-situ CVD,
- MoO₂/MoS₂ heterostructure,
- sulfurization,
- amorphous intermediate phase,
- metal-to-semiconductor phase evolution,
- 2D pyroelectrics

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