Empa work has just been published in the scientific journal Nature Chemistry. Led by Prof. Dr. Roman Fasel ( right) the scientists combined empirical observations using scanning tunnelling microscopy with computer simulations.

Electronic components are getting smaller, microelectronics gradually being replaced by nanoelectronics. But at nanoscale, silicon, at the present stage the most commonly used material in semiconductor technology, reaches a limit, preventing further miniaturisation and technological progress.

New electronic materials are therefore in great demand. Due to its outstanding electronic properties, graphene, a 2D carbon network, is considered as a possible replacement. But several obstacles need to be overcome before graphene can be used in semiconductor technology. For instance, currently there is no easily applicable method for large-scale processing of graphene-like materials.

Empa researchers of the nanotech surfaces Laboratory report on a surface chemical route to fabricate small fragments of graphene, so-called nanographenes.

Using a prototypical polyphenylene precursor, the researchers clarified, together with scientists at the Max Planck Institute for Polymer Research in Mainz (Germany) and the University of Zurich, how the reaction pathway runs in detail on a copper surface, and how the building blocks can be transformed into planar nanographenes directly on the surface.

Successful partners: experiment and simulation
For the investigations, researchers combined empirical observations, in particular from scanning tunnelling microscopy, with computer simulations. The simulations are used to determine whether a theoretically possible reaction step is energetically possible or not. The result: the reaction pathway consists of six steps with five intermediate products.

Two of them are stabilised by the surface so that they can be stably imaged with the scanning tunnelling microscope. The reaction barriers connecting the different intermediates are lowered through a catalytic effect of the substrate.

To be capable of being integrated in electronic circuits, the graphene-like material must however be manufactured on semiconductor surfaces instead of metal ones.

The researchers have simulated whether their approach could also work on these surfaces and the results are very promising, showing that surface-supported synthesis is a possible way to fabricate tailored nanographenes on a range of different substrates.

The three pillars of theory, experiment, and simulation
Computer-generated image shows details of one of the two intermediate products that the Empa researchers identified with the scanning tunnelling microscope.

Progress in today’s scientific research relies at the same time on theory, experiments, and to an increasing extent on computer simulations.

These simulations are complementary to often complex lab experiments and make it possible to get further information that cannot be obtained with experimental methods alone.

Combining experiments and simulations and the deduced theories allows for an increasingly accurate explanation and precise prediction of natural phenomena.