Direct synthesis of two-dimensional MoS2 on p-type Si and application to solar hydrogen production

• Published in: NPG Asia materials 2019-09, Vol.11 (1), p.1-9, Article 47
• Main Authors: Hasani, Amirhossein, Le, Quyet Van, Tekalgne, Mahider, Choi, Min-Ju, Lee, Tae Hyung, Jang, Ho Won, Kim, Soo Young
• Format: Article
• Language: English
• Subjects: 140/146; 639/301/299/890; 639/925/357/1018; Biomaterials; Chemistry and Materials Science; Clean energy; Corrosion resistance; Crystallization; Electronic devices; Energy Systems; Heterojunctions; Hydrogen fuels; Hydrogen production; Integrated circuits; Materials Science; Molybdenum; Molybdenum disulfide; Molybdenum oxides; Optical and Electronic Materials; Photoelectric effect; Photoelectric emission; Semiconductors; Silicon; Silicon junctions; Silicon wafers; Single crystals; Structural Materials; Surface and Interface Science; Synthesis; Thin Films; Transition metal compounds; Two dimensional materials; Wafers; Water splitting
• ISSN: 1884-4049; 1884-4057
• DOI: 10.1038/s41427-019-0145-7

Transition metal dichalcogenides (TMDs) are promising two-dimensional (2D) materials, and MoS 2 has been specifically utilized in electronic devices and integrated circuits. However, the direct synthesis of MoS 2 on traditional semiconductors, such as silicon, remains challenging due to the hydrophobic surface of nonoxide wafers (e.g., Si, GaAs, and InP). Herein, a novel, facile, reliable, and one-step method for the direct synthesis of single-crystal MoS 2 on a p -Si wafer via hybrid thermolysis is proposed. To demonstrate the applicability of the proposed method, a MoS 2 / p -Si heterojunction was fabricated and used for solar-driven hydrogen production. The as-fabricated n -MoS 2 / p -Si heterojunction exhibited a benchmark current density of −13.5 ± 1 mA/cm 2 at 0 V and an onset potential of +0.02 V. This method reliably and efficiently produced high-quality MoS 2 crystals on a wafer scale and is sufficiently simple to overcome the challenges associated with previous approaches. The method developed herein represents a tremendous advancement in the fabrication of 2D electronic devices. 2D semiconductors: Taming unruly crystals for green energy Solar panels that catalyze the splitting of water into hydrogen fuel and oxygen can now be fabricated using a simple deposition process. Interfaces between two-dimensional molybdenum disulfide (2D-MoS 2 ) and electron-poor silicon can split water using light, but only when the naturally random crystallization patterns of 2D-MoS 2 are inhibited. Researchers led by Ho Won Jang from Seoul National University and Soo Young Kim at Chung-Ang University, Seoul, have improved uniformity in this ultrathin material by initially coating silicon wafers with a molybdenum oxide precursor that adheres in smooth layers. By depositing a second, sulfur-rich coating and then heating the sample, the team produced uniform 2D-MoS 2 /silicon junctions down to 10-nanometer scales. The transparent device maintained a water-splitting photocurrent for over forty hours without degradation, thanks to the corrosion-resistant nature of high-quality 2D-MoS 2 crystals. A direct synthesis method for high-quality MoS 2 thin films on p-Si wafer is reported herein. To increase the hydrophilicity of the p-Si wafer, MoO 3 was deposited before spin-coating. The (NH 4 ) 2 MoS 4 precursor was easily coated onto the MoO 3 /p-Si and was converted to a MoS 2 /p-Si heterojunction via thermolysis. This method has the potential to be used in 2D electronic devi