Graphene has been called the "wonder material of the 21st century." Since its discovery in 2004, this single-layer carbon atom material has been highly praised for its many unique properties. However, the current mass-produced graphene has a disadvantage: the quality could be higher. Now, a joint research team from Colum bia University in the United States and the University of Montreal in Canada has developed a new method to purify graphene using oxygen-free chemical vapor deposition (OF-CVD) to mass-produce high-quality graphene. The relevant paper was published in the journal Nature on the 29th.
The Hone laboratory at Colum bia Engineering created more than 100 identical graphene samples using oxygen-free chemical vapor deposition.
Image source: Colum bia University
This study shows how trace oxygen affects the growth rate of graphene and, for the first time, determines the connection between oxygen and graphene quality. Experiments show that to synthesize high-quality graphene using chemical vapor deposition (CVD), it is key to remove oxygen during the growth process. This discovery may be a milestone in the mass production of graphene.
There are two ways to make graphene, one of which is the "scotch tape method." Use household tape to "tear" different layers from graphite. The graphene peeled off by this method is very clean and does not contain impurities that affect its performance. Still, it is only tens of microns wide, which is only suitable for laboratory research and not for industrial-scale production.
In order to explore how graphene production can move from the laboratory to real-world applications, researchers developed a method for synthesizing large-area graphene about 15 years ago. This process is called chemical vapor deposition (CVD) growth. At a sufficiently high temperature (about 1000°C), a carbon-containing gas (such as methane) is passed through the copper surface to decompose the methane and rearrange the carbon atoms to form a single honeycomb graphene layer. The CVD growth method can be scaled up to produce graphene samples that are several centimeters or even meters in size. However, the quality of samples synthesized by the CVD growth method has problems such as poor consistency and insufficient stability.
This time, the research team found that whenever trace amounts of oxygen were eliminated, the growth rate of graphene would be much faster. After further analysis, they developed a simple model that can predict the growth rate of graphene under different parameters (gas pressure, temperature, etc.).
They improved the existing CVD system and produced graphene of very high quality, almost identical to graphene "torn" from tape, and showed fractional quantum Hall effect in a magnetic field.
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