Water molecules interfere with electrical resistance of graphene, but a team of European scientists has found that when this two-dimensional material is integrated with the metal of the circuit, the contact resistance is not disturbed by moisture. This finding will help develop new sensors – the interface between the circuits and the real world – with significant cost savings.
Many applications of graphene, the atomic thin layer of carbon atoms with extraordinary conductivity and mechanical properties, include the manufacture of sensors. They convert environmental parameters into electrical signals that can be processed and measured using a computer.
Due to their two-dimensional structure, graphene sensors are extremely sensitive and promise good performance at low cost in the coming years.
To achieve this, graphene must create effective electrical contacts when integrated with a conventional electronic circuit. Such proper contacts are decisive in each sensor and significantly affect its performance.
However, there is a problem: graphene is sensitive to moisture, to molecules of water in the ambient air that are adsorbed on its surface. H2The molecule changes the electrical resistance of this carbon material, which introduces a false signal into the sensor.
However, Swedish scientists have found that when the graph binds to the metal of electronic circuits, the contact resistance (part of the total material resistance due to incomplete interface contact) is not affected by moisture.
"It will make life easier for sensor designers because they will not have to worry about the impact of moisture on the contacts, just about the graphene itself," explains Arne Quellmalz, a PhD student at the KTH Royal Institute of Technology (Sweden) and chief research officer.
A study published in the journal Applied materials and ACS interface, was performed experimentally using graphene together with gold metallisation and quartz substrates in model transmission transmission test structures as well as computer simulations.
"By combining graphene with conventional electronics, you can take advantage of the unique graphene features and low cost conventional conventional circuits," says Quellmalz. "One of the ways to combine these two technologies is to place graphene on the final electronics, rather than putting metal on the top of the graphene."
As part of the European CO2-DETECT, the authors apply this new approach to creating the first prototypes of graphene-based sensors. More specifically, the objective is to measure carbon dioxide (CO2), the main greenhouse gas, by means of optical detection of medium infrared light and at lower cost than other technologies.
In addition to the KTH Royal Institute of Technology, SenseAir AB from Sweden and Amo GmbH from Germany also participate in the CO2-DETECT, as well as the Barcelona Catalonian Institute of Nanotechnology (ICN).