A team of researchers at the Ulsan National Institute of Science and Technology (UNIST) has developed a technology to effectively fabricate a graphene quantum dot, which is an ultra-fine semiconductor particle.
Professor Shin Hyun-seok of the Department of Natural Science at UNIST said on Jan. 16 that his team succeeded in developing a two-dimensional planar complex manufacturing technology that regularly arranges graphene quantum dots in a single layer of hexagonal boron nitride (a material in which nitrogen and boron are combined in a hexagonal honeycomb shape) .
Shin said, "The graphene quantum-dot-based single-electron transistor will be applied to electronic devices that operate through fast information processing at low power.”
Graphene refers to a new material with a structure in which the carbon atoms are bonded in a hexagon. Graphene quantum dots are semiconductor nanoparticles with a size of several nanometers (nanometer or 1 nm is one billionth of a meter), and they have the characteristic of being luminescent when current is applied or light is emitted. These particles have been receiving attention as future materials of next-generation displays, bio-imaging, and sensors. They can also be applied to next generation quantum information communication technology, which processes information quickly while using less electricity.
Until now, graphene quantum dots have been made by peeling thin layers of graphite masses through physical and chemical reactions. In this case, it is difficult to obtain graphene quantum dots of desired size, and various impurities attached to the edges obstructed electron flow. As a result, it was difficult to fully utilize inherent electrical and optical characteristics of graphene quantum dots.
Professor Shin's research team solved this problem by placing hexagonal boron nitride on silica (SiO₂) substrates with platinum nanoparticles arrayed and heat-treating them in methane (CH4) gas. As a result, the size of graphene quantum dots was decided according to the size of the platinum particles, and graphene quantum dots were regularly arranged inside the hexagonal boron nitride of an atom layer.
The team fabricated a uniform array of graphene quantum dots using this technology and was able to adjust the size to 7 nm to 13 nm. It also succeeded in implementing a single electron transistor (a component of integrated circuit that controls only one electron to transmit a signal) that minimizes impurities to move electrons stably.