10-07/08 :: July/August 2010
nanotimes News in Brief
Materials // Nanoribbons for Graphene Transistors
S
cientists from Empa, the Max Planck Institute for Polymer Research in Mainz (Germany), ETH
Zurich and the Universities of Zurich und Bern (Switzerland) have now developed a new method for creating graphene ribbons with band gaps.
The scientists describe in Nature a simple surface- based chemical method for creating such narrow ribbons without the need for cutting, in a bottom- up approach, i.e. from the basic building blocks. To achieve this, they spread specifically designed halo- gen-substituted monomers on gold and silver surfaces under ultrahigh vacuum conditions. These are linked to form polyphenylene chains in a first reaction step.
In a second reaction step, initiated by slightly higher heating, hydrogen atoms are removed and the chains interconnected to form a planar, aromatic graphene system. This results in graphene ribbons of the thick- ness of a single atom that are one nanometre wide and up to 50nm in length. The graphene ribbons are thus so narrow that they exhibit an electronic band gap and therefore, as is the case with silicon, possess switching properties – a first and important step for the shift from silicon microelectronics to graphene nanoelectronics. And if this wasn’t enough, gra- phene ribbons with different spatial structures (either straight lines or with zig-zag shapes) are created, de- pending on which molecular monomers the scientists used.
Now, the scientists want to start investigating proper- ties of the graphene ribbons, for instance how the magnetic properties of the graphene ribbons can be influenced by different edge structures. The surface- based chemical method also opens up interesting possibilities with regard to the targeted doping of graphene ribbons: the use of monomer components with nitrogen or boron atoms in well-defined posi- tions or the use of monomers with additional func- tional groups should enable the creation of positively and negatively doped graphene ribbons.
A combination of different monomers is also possi- ble and may permit, for example, the creation of so called heterojunctions, which could be used in solar cells or high frequency components. The scien- tists have already demonstrated that the underlying principle for this works: they have connected three graphene ribbons to each other at a nodal point by means of two suitable monomers.
To date, the scientists have focused on graphene ribbons on metal surfaces. However, to be usable in electronics the graphene ribbons need to be created on semi-conductor surfaces or methods must be de- veloped to transfer the ribbons from metal to semi- conductor surfaces. And first results in this direction also give the scientists good reasons to be optimistic.
59
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38 |
Page 39 |
Page 40 |
Page 41 |
Page 42 |
Page 43 |
Page 44 |
Page 45 |
Page 46 |
Page 47 |
Page 48 |
Page 49 |
Page 50 |
Page 51 |
Page 52 |
Page 53 |
Page 54 |
Page 55 |
Page 56 |
Page 57 |
Page 58 |
Page 59 |
Page 60 |
Page 61 |
Page 62 |
Page 63 |
Page 64 |
Page 65 |
Page 66 |
Page 67 |
Page 68 |
Page 69 |
Page 70 |
Page 71 |
Page 72 |
Page 73 |
Page 74 |
Page 75 |
Page 76 |
Page 77 |
Page 78 |
Page 79 |
Page 80 |
Page 81 |
Page 82 |
Page 83