Changing the crystalline surface beneath a MoS2 film was associated with strikingly different growth patterns, according to an arXiv preprint. Under the same nominal deposition, calcination and high-temperature sulfurization conditions, SrTiO3 showed numerous small domains of approximately 5 µm that coalesced into a nearly continuous film. TiO2 showed reduced nucleation and star-like domains that could exceed 500 µm. MgO showed relatively sparse, dendritic domains extending over hundreds of micrometers, while SiC showed low-coverage triangular growth, including domains greater than 100 µm.
The coverage estimates reinforced the contrast. SrTiO3 had approximately 66% monolayer and 23% multilayer coverage. TiO2 had 44.3% monolayer and 23.7% multilayer coverage. MgO had approximately 49% monolayer and 28% multilayer coverage, while SiC had approximately 15.1% monolayer and 7.2% multilayer coverage. Here, monolayer and multilayer refer to single-layer and multiple-layer regions.
Same process, different surfaces
The comparison used five crystalline substrates: Al2O3 (0001), SrTiO3 (100), rutile TiO2 (001), MgO (100) and 6H-SiC (0001). In the liquid-precursor setup, a molybdenum precursor was pre-deposited on each substrate, sulfur was supplied from the vapor phase during high-temperature sulfurization, and all substrates received the same nominal deposition, calcination and sulfurization conditions. Coverage was quantified by threshold-based segmentation of ten 200 µm × 200 µm optical micrographs per substrate. At least five high-signal-to-noise photoluminescence and Raman spectra were acquired.
The light signal changed, too
The optical signal changed with the substrate as well. On TiO2, the Raman signature was weak, and photoluminescence was relatively sharp and blue-shifted. Its peak energy was 1.88 ± 0.02 eV and its FWHM, a measure of peak width, was 0.08 ± 0.008 eV. On SiC, the red-shifted peak had an energy of 1.806 ± 0.014 eV and a FWHM of 0.126 ± 0.048 eV. Raman analysis reported a tensile-strain indicator of 1.0 ± 0.2% and a p-type doping indicator of −0.28 ± 0.42 × 10^13 cm−2.
SrTiO3 showed broad, red-shifted photoluminescence, with an emission energy of 1.768 ± 0.104 eV and a FWHM of 0.174 ± 0.054 eV. Its reported strain and p-type doping indicators were −0.28 ± 0.31% and −0.66 ± 1.3 × 10^13 cm−2. MgO showed sharper and significantly blue-shifted photoluminescence despite its cratered morphology; the reported strain and p-type doping indicators were −0.77 ± 0.43% and −0.94 ± 0.84 × 10^13 cm−2.
The Raman-based strain and doping values in these comparisons are comparative indicators rather than absolute calibrations. The TiO2 estimate also needs caution because the substrate produces a strong Raman background. The proposed growth pathways are phenomenological, and the effective transport quantities in the framework are not directly measured.
A proposed growth picture
To organize the observations, the authors describe the process as substrate-influenced, reaction-diffusion-like growth. In this picture, an initial nucleation stage is associated with precursor wetting and anchoring, while later lateral growth is associated with effective sulfur transport and local conversion kinetics. That is a proposed way to connect the two stages, not a direct measurement of the high-temperature interface.
Taken together, the findings suggest that substrate choice may be a practical tuning variable for direct-growth MoS2, while the mechanisms remain unsettled. The available results do not identify a single substrate property as the explanation for any one morphology or optical response. Direct measurements of sulfur transport, activation energies and precursor binding energies, along with tests on additional substrates and process conditions, would be needed to assess how widely the reported regimes apply.
Publication status
The document is arXiv:2608.28269v1, dated 28 August 2026. The authors declare no conflicts of interest. Its data statement says supporting data are publicly available under a placeholder marked [DOI].
Paper data and sources
Original title: Phenomenological Growth Regimes in Liquid-Precursor CVD of MoS$_2$ on Functional Substrates
Authors: Osamah Kharsah, Kilian Mouchel, Yossarian Liebsch et al.
Journal/Repository: arXiv
Status: Preprint, not yet peer-reviewed
First online: 2026-08-28
DOI: Not available
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