Researchers captured real-time images of monolayer two-dimensional semiconductors growing inside a microreactor, revealing how molten precursor droplets drive crystal formation at the atomic scale. Credit: Dr. Hiroo Suzuki from Okayama University, Japan

As the miniaturization of silicon-based semiconductor devices approaches fundamental physical limits, the electronics industry faces an urgent need for alternative materials that can deliver higher integration and lower power consumption. Two-dimensional (2D) semiconductors, which are only a single atom thick, have emerged as promising candidates due to their unique electronic and optical properties. However, despite intense research interest, controlling the growth of high-quality 2D semiconductor crystals has remained a major scientific and technological challenge.

A research team led by Research Associate Professor Hiroo Suzuki from the Department of Electrical and Communication Engineering at Okayama University, Japan, together with Dr. Kaoru Hisama from Shinshu University and Dr. Shun Fujii from Keio University, has now overcome a key barrier by directly observing how these materials grow at the atomic scale. Using an advanced in situ observation system, the researchers captured real-time images of monolayer transition metal dichalcogenides (TMDCs) forming inside a micro-confined reaction space. The study was published on December 12, 2025, in the journal Advanced Science.

The work builds on earlier success by the team in synthesizing large-area monolayer TMDC single crystals using a substrate-stacked microreactor. While that method consistently produced high-quality materials, the mechanisms governing crystal growth inside the confined space were poorly understood.

"We could make excellent crystals, but we did not know exactly how they were forming," said Dr. Suzuki. "Without that understanding, it is difficult to reliably design materials for specific device applications."

In R1, in situ observation revealed that the crystal maintained its triangular shape during growth. Credit: Advanced Science (2025). DOI: 10.1002/advs.202516784

To address this gap, the researchers developed an infrared-heated chemical vapor deposition system that allowed them to observe crystal growth as it happened. By carefully tuning precursor concentration and sulfur supply, they identified multiple growth regimes with distinct crystal shapes and behaviors.

Under some conditions, conventional triangular crystals formed. Under others, large hexagonal crystals rapidly expanded with molten precursor droplets accumulating along their edges. In sulfur-rich environments, ribbon-like crystals emerged, bending and changing direction in response to atomic-scale features of the substrate.

One of the most striking observations was the dynamic behavior of molten precursor droplets. The team found that sulfur incorporation lowered the melting point and surface tension of the precursor, increasing droplet mobility. These droplets migrated across the substrate via surface tension gradients, known as the Marangoni effect, continuously feeding material into the growing crystal.

"Watching the droplets move and directly contribute to crystal growth was a turning point," Dr. Hisama explained. "It allowed us to confirm growth mechanisms that had previously only been inferred."

By revealing how crystal shape and quality depend on growth conditions, the study provides a practical framework for engineering two-dimensional semiconductors with unprecedented precision. This control is essential for overcoming current limitations in semiconductor integrated circuits, which are struggling to achieve further miniaturization and energy efficiency using silicon alone.

The implications extend beyond conventional electronics. Precisely engineered 2D semiconductors could lead to faster and more power-efficient smartphones, flexible and wearable sensors, and compact local power generation devices. In the longer term, the findings may support the development of highly integrated, low-energy semiconductor platforms for artificial intelligence and Internet of Everything systems, including advanced monitoring technologies in healthcare and welfare sectors.

Dr. Suzuki emphasized the significance of the study and said, "This research shows that direct observation is the key to true materials control. By understanding how two-dimensional semiconductors grow, we can design the next generation of electronic devices from the atomic level upward."

Publication details

Hiroo Suzuki et al, Inside the Microreactor: In Situ Real‐Time Observation of Vapor–Liquid–Solid Growth of Monolayer TMDCs, Advanced Science (2025). DOI: 10.1002/advs.202516784

Citation: Real-time view inside microreactor reveals 2D semiconductor growth secrets (2026, February 2) retrieved 2 February 2026 from https://phys.org/news/2026-02-real-view-microreactor-reveals-2d.html

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