KAIST Institute For NANOCENTURY
- KAIST researchers reveal how laser annealing technology leads to the synthesis of graphene from silicon carbide (SiC).
The laser annealing technology has been adopted in mass-manufactured displays, like shiny flat AMOLED displays in our smart phones. Interestingly, a similar procedure can be used to generate ultrathin nanometerials, represented by graphene. Graphene is a strong and thin nanomaterial made of carbon, its electric and heat-conductive properties have attracted the attention of scientists worldwide.
Prof. Sung-Yool Choi and Prof. Keon Jae Lee's joint research group at the Center for Advanced Materials Discovery towards 3D Displays (CAMD3) discovered a mechanism of graphene synthesis, using a solid-state phase separation of single-crystal SiC, which is induced by a laser-material interaction. This study, published in Nature Communications, demonstates how this laser technology separate a complex compound (SiC) into two ultrathin layers of carbon and silicon. Although several fundamental studies have led fundamental understanding of the effect of excimer lasers in transforming elemental materials like silicon, the laser interaction with more complex compounds like SiC has rarely been studied due to the complexity of compound phase transition and ultra-short processing time
▲ High-resolution transmission electron microscopy shows that after just one laser pulse of 30 nanoseconds, the silicon carbide (SiC) substrate is melted and separates into a carbon and a silicon layer. More pulses cause the carbon layer to organize into graphene and the silicon to sublime.
With high resolution transimission electron microscope images and
molecular dynamic simulations, the researchers found that a single-pulse (30
nanoseconds) irradiation of xenon chloride excimer laser melts the surface of SiC,
leading to the separation of a liquid SiC layer, a disordered carbon layer with
graphitic domains (about 2.5 nm thick) on top surface and a polycrystalline
silicon layer (about 5 nm) below carbon layer. Giving additional pulses causes
the sublimation of the separated silicon, while the disordered carbon layer is
transformed into a multilayer graphene.
Prof. Choi and Lee said that "This research shows that the laser material interaction technology can be a powerful tool for next generation of two dimensional nanomaterials," and "Using laser-induced phase separation of complex compounds, new types of two dimensional materials can be synthesized in the future."
▲ Molecular dynamics simulates the graphene
formation mechanism. The carbon layer on the top forms because the
laser-induced liquid SiC (SiC (l)) is unstable.
Prof. Sung-Yool Choi / Prof. Keon Jae Lee