Researchers at North Carolina State University have developed a technique that enables the integration of graphene, graphene oxide (GO) and reduced graphene oxide (rGO) onto silicon substrates at room temperature by using nanosecond pulsed laser annealing. The advance may open the door to the possibility of creating new electronic devices, such as smart biomedical sensors.
In this new technique, the researchers start with a silicon substrate. They top that with a layer of single-crystal titanium nitride, using domain matching epitaxy to ensure the crystalline structure of the titanium nitride is aligned with the structure of the silicon. They then place a layer of copper-carbon alloy on top of the titanium nitride, again using domain matching epitaxy. Finally, the researchers melt the surface of the alloy with nanosecond laser pulses, which pulls carbon to the surface.If the process is done in a vacuum, the carbon forms on the surface as graphene; if it is done in oxygen, it forms GO; and if done in a humid atmosphere followed by a vacuum, it forms as rGO. In all three cases, the carbon's crystalline structure is aligned with the underlying copper-carbon alloy. The researchers can control whether the carbon forms one or two layers on the surface of the material by manipulating the intensity of the laser and the depth of the melting.
The team states that this process can easily be scaled up; so far they have made wafers that are two inches square, and could reportedly make them much larger, using lasers with higher Hertz at room temperature, which drives down the cost.
"We have already patented the technique and are planning to use it to develop smart biomedical sensors integrated with computer chips,"the researchers say.