High-resolution transmission electron microscope observations show that just after a 30-nanosecond laser pointer pulse, the silicon carbide substrate melted and separated into a carbon layer and a silicon layer. More pulses cause the carbon layer to organize into graphene, while the silicon leaves as a gas.
All our smart phones have shiny displays. Hidden behind each pixel of these displays are at least two silicon transistors manufactured in batches using laser pointer annealing technology. Traditional methods usually use temperatures higher than 1000°C to manufacture them, while laser technology can achieve the same results at low temperatures, even on plastic substrates (melting temperatures below 300°C). Interestingly, a similar process can also be used to produce graphene crystals. Graphene is a strong and thin nanomaterial made of carbon. Its electrical and thermal conductivity have attracted the attention of scientists from all over the world.
The research team of professors from the Institute of Basic Science (IBS) Multidimensional Carbon Materials Center and the team of professors from the Korea Advanced Institute of Science and Technology have discovered the mechanism of using laser-induced solid phase separation of single crystal silicon carbide (SiC) to synthesize graphene. This research paper published in "Nature Communications" explains how this laser pointer technology can separate a complex compound (silicon carbide) into ultra-thin components of carbon and silicon.
Although several basic studies have understood the effect of excimer lasers in transforming elemental materials such as silicon, the interaction between lasers and more complex compounds such as silicon carbide is still due to the complexity of the phase transition of the compound and the ultra-short processing time. It is rarely studied.
Through high-resolution microscopy images and molecular dynamics simulations, scientists have discovered that a single pulse of 30 nanosecond xenon chloride excimer green laser pointer can melt SiC, which leads to the separation of the liquid SiC layer, resulting in a non-volatile surface on the upper surface. Ordered carbon layer (about 2.5 nanometers thick) with graphite domains and a polysilicon layer (about 5 nanometers) below the carbon layer. Applying an additional pulse causes the separated silicon to sublime, and the disordered carbon layer is converted into multilayer graphene.
"This research shows that the technology of laser-material interaction can be a powerful tool for the next generation of two-dimensional nanomaterials," said Professor Keon. Professor Choi added: “The laser pointer is used to induce phase separation of complex compounds, and new types of two-dimensional materials can be synthesized in the future.” Professor Keon of IBS belongs to the School of Materials Science and Engineering of KAIST, and Professor Choi belongs to the Electrical School of Engineering and Graphene Research Center.