Synthesiology - English edition

−75− Synthesiology English edition Vol.6 No.2 pp.75-83 (Sep. 2013) Then, in 1993, “single-wall CNTs” were discovered. In CNT research, the theoretical calculations were done actively due to their relatively simple molecular structure. From the calculations, it was predicted that, despite being a substance consisting solely of carbon atoms, CNTs would have extremely excellent properties such as lighter weight and lower density than aluminum, over 10 times the strength of steel, higher electroconductivity than copper, as well as diverse properties including high thermal conductivity, high thermal stability, and high chemical stability. Also, the theoretical calculation predicted that they would behave like metals or semiconductors due to their arrangement (structure) of the carbon atoms. As mentioned above, since CNTs are nanomaterials with excellent potential, expectation is increasing for their new applications that cannot be achieved by other materials. Particularly looking at the electronics application, metallic CNTs, when made into thin film, do not require rare metal like the current transparent conductive film, and can be used as a transparent conductive film that can be bent due to their high mechanical strength. For semiconducting CNTs, high-speed transistor can be fabricated easily by coating, and a transparent and f lexible film can be created in this case also. However, there are barriers in the electronic application of CNTs. That is, using the conventional CNT synthesis method, the selective synthesis of metallic CNTs or semiconducting CNTs is not possible, and the result obtained is a mixture of metallic and semiconducting products (normally, ratio of metallic:semiconducting is 1:2). Therefore, research for the separation of metallic and semiconducting CNTs is crucial.