Tapered nano-sized ribbons have been made by tearing sheets of graphene from a sticky surface. The knowledge gained can be used to make better electronic devices such as mobile phones.
Graphene is a relatively new material that has physicists and materials scientists feverish with excitement. It consists of a two-dimensional sheet of carbon atoms, and has exceptional electronic and mechanical properties. It is widely hoped that graphene will one day be used in many electronic devices, heralding a new era for this technology and allowing devices to be made smaller, lighter, and more portable than ever. It is also incredibly stiff in one direction, so could also be useful for many construction or military purposes.
Graphene is commonly produced by one of two methods. The original and easiest of these involves tearing individual sheets off the top of a piece of layered carbon called graphite (this way is known as the Scotch tape method as a piece of sticky tape is used to lift the top layer away). Scientists at MIT and University of Manchester have used a mixture of simple experiments and a new kind of theoretical modelling to look at what happens when the layers of graphene are torn. Existing methods of modelling did not cope well with a two-dimensional sheet like graphene.
Markus Buehler and his colleagues found that the exact shape of the tiny ribbons depends on the stickiness of the surface that they are torn from and also on the number of layers that were on the surface. They measured the angle at which the sheet of graphene is torn off the surface, and found that this increases in size with both the surface stickiness and the number of layers present. From their results, the scientists can now predict the tearing angle and thus the shape of the nanoribbons that will be made in the future.
The team also found that the roughness and shape of the edges of the ribbons was affected by the stickiness of the surface used to peel the graphene layer off. The structure of the ribbon edge could be particularly important for the conductive properties of the ribbon, and affect its use in electronics.
This work gives an important fundamental insight into the processes used to make graphene; a material that is sure to be a vital ingredient of the electronics industry before too long. Understanding how to control graphene formation should enable technologists to turn graphene production into an industrial process and give us all cheaper, smaller, and better electronic components for everyday devices, such as cell phones.
Further background information on this subject can be found in a recent review article published by Professor Manish Chhowalla and Dr. Goki Eda.