Developed world’s first 2D material’s synthesis method utilizing plasma
Key technology for production cost reduction and mass production for next generation IT devices 
Published in the journal of ‘Advanced Materials’ August 10th online 

Sungkyunkwan University (SKKU) Department of Mechanical Engineering’s Profs. Kim, Tae Sung, & Prof. Lee, Changgu’s joint research team developed a technology which directly synthesizes 2 dimensional(2D) material, molybdenum disulphide (MoS2) on a plastic substrate, which is the first ever in the world. MoS2, due to their transparency and flexibility, is considered as the dream material that can replace silicon. Synthesizing MoS2 was usually done at high temperatures of 600℃ ~ 1000℃, and because of this, making it directly on flexible materials like plastics were impossible and had to go through a complicated process. The SKKU research team’s 2D material synthesis technology through chemical vapor deposition, has completely overcome the problems and made it possible to synthesize the material at a temperature of 150℃, which many plastics can most possibly endure. Because it’s broadly applicable to next generation electronic devices such as transparent, flexible and wearable electronic devices, this method is estimated to be a key technology for the manufacturing of transparent, flexible, paper like tablet PCs at low cost and with efficiency.

In the existing manufacturing process, MoS2 should be first synthesized on inorganic substrate due to the high synthesis temperature and then the synthesized film should be transferred on a flexible substrate. However, the transfer method accompanies a tear or a flaw, thus it was extremely difficult to produce a quality material, creating a big obstacle to commercialization of large area 2D material. The new method developed by the research team needs no transfer process, making it a ground-breaking technology, which produces high quality material through a simple manufacturing process and low cost .

“The existing plasma chemical vapor deposition method was ordinarily applied to insulation thin film compounding such as oxide or nitride films in semiconductor manufacturing, but through this research we were able to synthesize a nanometer thick semiconductor thin film on a plastic substrate.” explained the co-first author Ph.D. student Ahn Chi sung(SAINT) and Ph.D. student Lee, Jin hwan (Department of Mechanical Engineering) They went on to say that “this research is a ground breaking technology that enables the low cost, mass production of flexible electric material/ devices and others with utilizing existing semiconductor manufacturing facilities to produce insulation thin film or 2D semiconductor film through low temperature direct deposintion on plastic substrate.”
This technology was patented June of last year, while the patent application for US and China was made on November of last year.

Originally, plasma assisted synthesis method for 2D material was first attempted on graphene, but with the minimal needed heat coming around 400℃, direct deposition on plastic was impossible. Also the material’s quality was too low, giving it too many limitations for application. The research team’s method was to first apply molybdenum on a plastic (polyimide) substrate through vacuum adhesion, and then place the plastic substrate in a plasma chemical vapor deposition device and apply 150℃ of heat while infusing hydrogen and hydrogen disulfide to create the plasma and have the molybdenum and sulfur react. Through this, 5 ~ 6 layers of 2D MoS2 film was evenly formed over a 4 inch substrate. The film showed a charge mobility of about 2~4 cm2/Vs, whose high performance was not different from the high quality material manufactured at high temperatures. With the synthesized film a humidity sensor was developed and through its reliable operations it was proven that it can be directly used as a electrical material.

This research was supported by the Basic Research Project of the Global Frontier Softelectronic research group, the Ministry of Science, ICT & Future Planning and National Research Foundation of Korea, and was published in the prestigious journal of the field of materials, ‘Advanced Materials’ August 10 online edition.