by Anton Shilov
01/30/2014 | 11:47 PM
Graphene, one of the world’s thinnest electronic nanomaterials, has long held the promise as a wonder material in everything from flexible touchscreens to super-fast circuits. IBM researchers have demonstrated one of the first working prototype chips made of graphene. They created a logic circuit that was reliable enough to send and receive a text message.
The demonstration has the potential to improve today’s wireless devices’ communication speed, and lead the way toward carbon-based electronics device and circuit applications beyond what is possible with today’s silicon chips. Integrating graphene radio frequency (RF) devices into today’s low-cost silicon technology could also be a way to enable pervasive wireless communications allowing such things as smart sensors and RFID tags to send data signals at significant distances.
IBM Research-designed multi-stage graphene RF receiver integrated circuit consists of three graphene transistors, four inductors, two capacitors, and two resistors. All circuit components are fully integrated into a 0.6mm2 area and fabricated in a 200mm silicon production line, showing the unprecedented graphene circuit complexity and highest silicon CMOS process compatibility.
Circuits built on graphene could allow mobile devices – tablets to wearables – to transmit data much faster, in a more cost-effective manner, than today’s silicon-based chips. For example, the circuits we built for wireless receivers consume less than 20mW power to operate, while also demonstrating the highest conversion gain of any graphene RF circuits at multiple GHz frequency – successfully receiving and restoring a digital text message (“I-B-M”) carried on a 4.3GHz signal without any distortion.
Fabrication of a true integrated circuit is challenging because it is easy to damage a sheet of graphene during the fabrication flow of conventional integrated circuits. So, while IBM had shown it was possible to build an analog graphene integrated circuit with a broadband frequency mixer in a 2011 proof of concept, the graphene transistor performance was inevitably degraded due to the harsh fabrication processes.
Tilted view scanning electron microscopic (SEM) image revealing the integration of key components in IC with enlarged view showing the advanced gate structure of the graphene field-effect transistors (GFET). Inset image shows crosssectional SEM of embedded T-shaped gate. Scale bar, 500nm.
The IBM team decided to flip their approach by completely reversing the conventional silicon integrated circuit fabrication flow, leaving graphene transistors as the last step of integrated circuit fabrication. This resulted in preserving graphene device performance. It resulted in the first time that graphene devices and circuits could perform modern wireless communication functions comparable to silicon technology.