Water molecules distort the electrical resistance of graphene, but a team of European researchers found that when this two-dimensional material is integrated into the metal of a circuit, contact resistance is not impaired by moisture. This discovery will help develop new sensors – the interface between circuits and the real world – with significant cost savings.
The many applications of graphene, an atomically thin layer of carbon atoms with extraordinary conductivity and mechanical properties, include the fabrication of sensors. These transform environmental parameters into electrical signals that can be processed and measured with a computer.
Due to their two-dimensional structure, graphene-based sensors are extremely sensitive and promise good performance at low manufacturing cost in the coming years.
To achieve this, graphene needs to make efficient electrical contacts when integrated with a conventional electronic circuit. Such appropriate contacts are crucial to any sensor and significantly affect its performance.
But a problem arises: graphene is sensitive to moisture, the water molecules in the surrounding air that are adsorbed on its surface. H2The molecules change the electrical resistance of this carbon material, which introduces a false signal into the sensor.
However, Swedish scientists have found that when graphene binds to the metal of electronic circuits, contact resistance (the part of the total resistance of a material due to imperfect interface contact) is not affected by moisture.
"This will make life easier for sensor designers, as they will not have to worry about the humidity that influences contacts, just the influence on graphene itself," explains Arne Quellmalz, PhD student at KTH Royal Institute of Technology (Sweden). ). the main researcher of the research.
The study, published in the journal Applied Materials and ACS Interfaces, was performed experimentally using graphene in conjunction with gold metallization and silica substrates in transmission line model test structures as well as computer simulations.
"By combining graphene with conventional electronics, you can take advantage of the unique properties of graphene and the low cost of conventional integrated circuits." Quellmalz says, "One way to combine these two technologies is to place the graphene on top of the finished electronics. , rather than depositing the metal at the top of the graphene sheet. "
As part of CO2Project -DETECT, the authors are applying this new approach to create the first prototypes of graphene-based sensors. More specifically, the objective is to measure carbon dioxide (CO2), the main greenhouse gas, through optical detection of medium infrared light and at lower costs than with other technologies.
In addition to the KTH Royal Institute of Technology, Sweden's SenseAir AB and Amo GmbH from Germany also participate in CO2Project -DETECT, as is the Catalan Institute of Nanotechnology (ICN) of Barcelona.