Chinese scientists hit breakthrough on 2D semiconductor wafers

Chinese researchers have announced a new technique to mass produce 2D material wafers, paving the way for high-performance electronics using a successor to silicon. As semiconductor chips evolve, transistor sizes are approaching the physical limits of silicon-based technology. The search for next-generation semiconductor materials that can deliver superior performance has become a global priority. Among the candidates, two-dimensional (2D) materials such as molybdenum disulfide (MoS₂) with their atomically thin structure are regarded as promising successors for the post-Moore’s Law era because of their high carrier mobility and low power consumption. However, one of the core obstacles to commercialisation has been the difficulty of producing them uniformly over large areas and at a high quality. A team led by Wang Jinlan from Southeast University in Nanjing, working with Wang Xinran and Li Taotao from Nanjing University, announced a critical breakthrough last month. They introduced a novel crystal growth technique and fabricated a 6-inch (15cm) single-crystalline MoS₂ wafer, providing a route to the mass production of 2D semiconductors. In laboratories, MoS₂ crystals are usually made through chemical vapour deposition (CVD) in which gaseous raw material is introduced into a chamber and adsorbed onto a substrate to form a thin film or crystal. However, lab-made samples are often too small and inconsistent, making them impractical for large-scale production. To address these issues, scientists turned to metal-organic chemical vapour deposition (MOCVD), which uses metal-organic precursors and has enabled the growth of 8-inch films. Yet, crystals produced this way often contain numerous defects, and the decomposition of the metal-organic compounds introduces carbon impurities that contaminate the crystal lattice. Wang’s team discovered that a specific step in the crystallisation process acted as a major “bottleneck” – requiring high energy input that severely limited both the growth speed and the final crystal quality. They found that introducing oxygen into the reaction could bypass this demanding pathway, effectively creating a detour that significantly lowered the energy barrier. The team named this new method “oxy-MOCVD”. Using it on a sapphire substrate, they grew a uniform 150mm (6-inch) single-crystalline MoS₂ film. Experiments showed the growth rate exceeded that of conventional MOCVD by more than two orders of magnitude – over 100 times faster – and the resulting films were free of carbon impurities. Additional electrochemical tests confirmed the advantages of this approach. Field-effect transistor arrays fabricated from the 6-inch oxy-MOCVD MoS₂ single crystal showed a maximum electron mobility more than 10 times higher than those made with traditional MOCVD. According to the team’s paper, “this approach bridges the gap between lab-scale CVD quality and industrial-scale MOCVD scalability”, solving the critical challenge of large-area, uniform growth for 2D semiconductor mass production. The study was published in the peer-reviewed journal Science on January 29. In a complementary advance published in Science a week later, a team from the University of Science and Technology in Beijing reported a new technique allowing real-time observation of MoS₂ crystal growth under a transmission electron microscope (TEM). This method is expected to help further reduce crystal surface defects. Chinese research teams have contributed significantly to the exploration of various 2D semiconductor materials poised to replace silicon. In 2023, a team led by Liu Kaihui from Peking University in Beijing demonstrated batch production of MoS₂ wafers with diameters ranging from 2 to 12 inches using a substrate-stacking technique. In July last year, the same team proposed a new strategy to grow 2-inch single-phase indium selenide (In₂Se₃) wafers. Also last July, a team led by Zhou Peng and Bao Wenzhong from Fudan University in Shanghai developed the world’s first 32-bit RISC-V architecture microprocessor, named “Wuji”, based solely on 2D semiconductor materials. The processor executes standard 32-bit instructions using 5,900 MoS₂ transistors.

Chinese scientists hit breakthrough on 2D semiconductor wafers

.css-1c6uqr6{color:inherit;font-weight:inherit;font-size:inherit;font-family:inherit;line-height:inherit;overflow-wrap:break-word;}Quest for next-generation materials that can deliver superior performance in the coveted chips has become a global priority

Quest for next-generation materials that can deliver superior performance in the coveted chips has become a global priority