Researchers at UNIST and Sungkyunkwan University have developed a solution with excellent crystallinity.
Development of a technology to synthesize transition metal chalcogenides
Improve quality by using solid and liquid raw materials together


To accelerate the commercialization of next-generation semiconductor materials to replace silicon (Si), a team of Korean researchers has developed a technology for growing two-dimensional semiconductor materials at the atomic level in thin, wide, and uniform layers. They have also demonstrated this feasibility by fabricating actual semiconductor devices.

On the 8th, a research team led by Professor Hye-Sung Park of Ulsan National Institute of Science and Technology (UNIST) and Professor Joo-Hoon Kang of Sungkyunkwan University developed a technology to synthesize transition metal chalcogenide compounds with excellent atomic arrangement regularity by using both liquid and solid raw materials, unlike the existing method that only used solid raw materials.

Transition metal chalcogenides are attracting attention as next-generation semiconductor materials, but large-area synthesis is challenging. Chemical vapor deposition (CVD), which synthesizes using solid precursors that vaporize at high temperatures, has uneven vapor concentrations, making it difficult to obtain multiple films of identical quality. Furthermore, the size of the films that can be synthesized is limited. Therefore, methods utilizing liquid precursors are gaining attention.

However, when using liquid raw materials, there is a problem that the quality of the synthesized material, such as the regularity of the atomic arrangement, i.e. crystallinity, is reduced. Accordingly, the research team coated a liquid transition metal raw material onto a substrate and allowed it to react with the vapor-state chalcogen element.

Officials explained that the metal halide, a reaction accelerator in the liquid raw material, facilitated the chalcogenization reaction, making it easy to obtain a compound with excellent crystallinity. Furthermore, the use of the accelerator allowed the compound to grow only horizontally, rather than vertically, making it possible to synthesize a transition metal chalcogenide composed of only a single, thin layer.

The developed synthetic method can be used regardless of the type of transition metal chalcogenide. The research team synthesized various single-layer transition metal chalcogenides by varying the combination of transition metals such as molybdenum (Mo) and tungsten (W) and chalcogen elements such as sulfur (S) and selenium (Se).

In particular, the research team also demonstrated that semiconductor devices can be manufactured using synthesized semiconductor thin films. A field-effect transistor was fabricated using a molybdenum diselenide (MoSe2) thin film, and the excellent electron mobility of the thin film was confirmed.

Meanwhile, this study was published under the title 'High-Crystalline Monolayer Transition Metal Dichalcogenides Films for Wafer-Scale Electronics' in the February 23rd issue of 'ACS Nano', an academic journal in the field of nanomaterials.