Over the past ten years, graphene has attracted extensive attention and research because of its unique optical, mechanical and electrical properties. The only one carbon atom thick single-layer material to liberation of the electronic device, and is expected to produce a faster transistors, cheaper solar cells, new sensors and more efficient biological sensing device. Materials as potential contact electrode and the internal connection and graphene wafer is microelectronic circuits in an important part, but the vast majority of fabricated graphene methods are not suitable for in microelectronic devices, which hinders the graphene from the wonder material of the considerable potential to actual profit maker.
Now, it's from Korea University, Seoul, Korea University researchers developed a application in microelectronic devices simple process diameter is 4 inches, high quality, multi layer wafer graphene successfully synthesis in the silicon substrate. The method is based on the ion implantation technique, a method for accelerating the ion bombardment of a semiconductor material with an electric field. The results of high speed ion collisions with semiconductor materials can change the physical, chemical and electronic properties of the material.
This week in the journal Applied Physics Letters, published by the American Federation of physics, the researchers describe their research, which will promote the commercialization of graphene in the field of microelectronics.
"If you want to be the application of graphene in advanced silicon microelectronic devices, you need to the large area of wrinkle free, no cracks, no residue of graphene under the condition of low temperature synthesized on a silicon substrate, the traditional graphene synthesis technology needs high temperature conditions therefore does not apply," said the team leader, Korea University's Department of chemistry and biological engineering, Professor jihyun Kim. "Our work shows that carbon ion implantation technology has the potential to be one in microelectronic integrated circuit in direct synthesis of wafer graphene method."
Since ten years ago, graphene was discovered so far, it is considered the world's most thin, the lightest and most resilient material. The material is flexible and transparent, non-toxic and inexpensive, its conductivity can be comparable with copper, can at room temperature almost no resistance to conduction electrons, the nature has also become "ballistic transport" (Transport Ballistic). Due to its unique optical, mechanical and electrical properties, graphene is believed to be the first choice for the production of a new generation of faster, cheaper, less energy consuming electronic products.
"Graphene is used as a connecting material for semiconductor devices in potential contact electrodes and electronic circuits in silicon materials microelectronic devices," Kim said. This makes the processing method based on high temperature conditions does not apply, because the high temperature may bring the material damage, distortion, metal spikes and the diffusion of debris."
Therefore produced graphene of traditional technology and chemical gas phase deposition method although widely be applied in copper or nickel film on large area graphite synthetic ene, but this method does not apply in a silicon microelectronic devices, because chemical vapor deposition method needs above 1000 degrees Celsius in the temperature conditions are, even after the graphene from the metal substrate is transferred to the silicon substrate.
"Transfer to the graphene substrate target often have cracks, folds and contaminants," said Kim. "So we think it is necessary to study a kind of method that can not be transferred, which can synthesize high quality multilayer graphene directly in silicon micro electronics devices."
The Kim method is based on ion implantation technology, a technology compatible with microelectronic devices, which is generally used to mix impurities in a semiconductor material. In the process of ion implantation, the carbon ions are accelerated by electric field, and the silicon substrate with nickel layer and silicon oxide layer is bombarded with the temperature of 500 degrees Celsius. Nickel layer, because of its high carbon solubility, was used as a catalyst for the synthesis of graphene. Subsequently, whole sample after high temperature activation annealing treatment (about 600 to 900 degrees Celsius) to form honeycomb lattice structure between carbon atoms, is graphene microstructure characteristics.
Kim explained that the activation annealing temperature can be further reduced by increasing the temperature of the ion implantation process. By changing the ambient pressure, gas, temperature, and annealing time, Kim and his colleagues systematically studied the effects of various conditions on the synthesis of high quality multilayer graphene.
According to Kim, ion implantation technology is different from another aspect of other method is, it can be more precise control of the final structure, because graphene coating thickness can be controlled by carbon ion implantation dose and be accurately controlled.
"Our synthesis method is controllable and can be expanding and shrinking. This method enable us to produce silicon wafer with the same size graphene [diameter of more than 300 mm]," said Kim.
The next step for the researchers is to further reduce the temperature in the synthesis process and control the thickness of graphene in the production process.
