Monolayers of layered transition metal dichalcogenides (LTMDs) exhibit significant spin-valley coupling and optoelectronic performances that make them ideal materials for valley-based optoelectronic applications. This invention describes a method of synthesizing MoS2, a material with great potential for logic devices integrated circuits and optoelectronics, by way of the chemical vapor deposition (CVD) technique.
LTMDs such as MX2 (where M= Mo or W, X = S or Se) have applications in flexible electronics and optoelectronics, hybrid heterostructures with 2D materials, advanced semiconductor devices and integrated circuits, short-channel devices, valleytronics devices, battery and supercapacitors, and energy harvesting issues such as water splitting and hydrogen production.
Despite considerable efforts including various methods of exfoliation, physical vapor deposition and chemical vapor deposition, the synthesis of high-quality LTMD monolayers remains as a great challenge so far. Moreover, a robust transfer technique to avoid degradation in quality and contamination is essential for fundamental physics and optoelectronic applications. The inventors present a feasible synthetic process to overcome these challenges by directly synthesizing LTMD monolayers on various surfaces using scalable CVD processes. Not only is the growth successful for surfaces of different materials but it has been found that the deposition is applicable for surfaces with various morphology. A reliable transfer technique that uses PDMS and water as media enables MoS2 monolayer on flexible substrates or surfaces of various functional materials while maintaining their high quality.
Aromatic molecules, including reduced graphene oxide (r-GO), PTCDA, and PTAS, are used as a seeding layer on diverse surfaces. The aromatic seeds are suspended or solute in DI water and the optimized concentration for the growth of MoS2 monolayer is increased with growth temperature. Prior to the surface treatment, the samples are cleaned with piranha solution for making surface. Prior to the synthetic process, the substrates are treated with the seeds solutions. A monolayer of a MoS2, or some metal dichalcogenide, is grown via chemical vapor deposition on the growth substrate surface seeded with aromatic molecules. The seeded aromatic molecules are contacted with a solvent that releases the metal dichalcogenide layer from the growth substrate. The metal dichalcogenide layer can be released with an adhered transfer medium and can be deposited on a target substrate using PDMS and a tiny droplet of DI water.
- Numerous novel performances and unique optical properties are observed on the LTMD monolayer
- Direct growth of LTMD monolayer on divers surface nanostructures
- Scalable fabrication of high-quality LTMD monolayer
- Simple and low cost
- Low growth temperature
- No limitation on substrate