Water molecules distort the electrical resistance of graphene, but a team of European researchers has discovered that when this two-dimensional material is integrated with the metal of a circuit, contact resistance is not affected by humidity. This finding will help develop new sensors, the interface between the circuits and the real world, with a significant reduction in costs.
The numerous applications of graphene, a thin sheet 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 its two-dimensional structure, graphene-based sensors are extremely sensitive and promise good performance at low manufacturing costs 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 in any sensor and significantly affect their performance.
But a problem arises: Graphene is sensitive to moisture, water molecules in the surrounding air that adsorb on its surface. HtwoThe O molecules change the electrical resistance of this carbon material, which introduces a false signal into the sensor.
However, Swedish scientists have discovered that when graphene is attached to the metal of electronic circuits, the contact resistance (the part of the total resistance of a material due to imperfect contact at the interface) is not affected by humidity .
"This will make life easier for sensor designers, since they will not have to worry about the humidity that influences the contacts, only the influence on the graphene itself," explains Arne Quellmalz, a PhD student at the Royal Institute of Technology of KTH (Sweden) and The principal investigator of the investigation.
The study, published in the journal. Applied materials and interfaces of ACS, has been carried out experimentally using graphene together with gold metallization and silica substrates in test structures of transmission line models, as well as computer simulations.
"By combining graphene with conventional electronics, you can take advantage of both the unique properties of graphene and the low cost of conventional integrated circuits." says Quellmalz, "One way to combine these two technologies is to place the graphene on top of the finished electronics, instead of depositing the metal on the graphene sheet."
As part of the European COtwo-DETECT the project, the authors are applying this new approach to create the first prototypes of graphene-based sensors. More specifically, the purpose is to measure carbon dioxide (COtwo), the main greenhouse gas, by means of the optical detection of the average infrared light and at lower costs than with other technologies.
In addition to the KTH Royal Institute of Technology, companies SenseAir AB of Sweden and Amo GmbH of Germany also participate in the COtwo-Detects the project, as is the Catalan Nanotechnology Institute (CIE) of Barcelona.