IBM researchers have built the first integrated circuit (IC) based on a graphene transistor.
Graphene promises faster components to challenge the traditional silicon, but there are hurdles which need jumping. In October last year, scientists told us that Graphene had the potential to replace silicon in transistors as its transition speeds switch to hundreds of gigahertz and could even reach terahertz.
At the time, researchers said a replacement is a long way off.
IBM’s researchers, however, claim that with this breakthrough they are another step closer to fully working with the Nobel-prized material.
The circuits were made using existing manufacturing methods, which means there isn’t a need for a whole new construction process. Down the line, among other uses, graphene chips could enable faster, more power-efficient radio communications circuitry for mobile phones, and other wireless devices.
They made a frequency mixer circuit and married a graphene transistor with two metal devices, called inductors.
According to IBM researcher Yu-Ming Lin, the frequency mixer, currently used in mobiles to convert radio signals used to transmit information into a signal in a frequency the human ear can hear, was the main piece to the puzzle. By mixing the radio signal with a reference signal, the transistor was able to handle frequencies of up to 10 GHz.
It wasn’t plain sailing. IBM admitted that it struggled to integrate the graphene with other components. They said it was a “difficult engineering challenge” which took a year to overcome.
According to the IEEE, one of the problems was that graphene didn’t play very nicely with other metals, including aluminium, gold, and palladium which were used to make the rest of the circuit.
Another problem was that graphene is easily damaged by standard semiconductor etching processes.
However, the scientests were not deterred.
Instead they decided to “grow” the graphene on a silicon-carbide wafer.
To give it that extra strength they coated it with a polymer known as PMMA and a resist that could withstand the jets of electrons used in electron beam lithography. By doing this they were able to create a shield of strength around the graphene, which also meant it could withstand temperatures of around 127 °C.
As a result, a graphene circuit wouldn’t have to be over-designed to compensate for temperature changes.
They wouldn’t have to spend hours creating a complicated circuit, thus saving time and money.