Cambridgeshire-based Paragraf has had its graphene-based Hall magnetic field sensor tested for radiation toughness by the National Physical Laboratory (NPL).

PAR3_Paragraf’s-packaged-graphene-Hall-sensors

“Tests conducted by NPL have shown that following exposure to a neutron dose of 241mSv/hr, which is about 30,000 times the expected typical neutron dose rate in the International Space Station, Paragraf’s sensors are not affected by this level of radiation,” according to the company. “This is the first time that a commercially available graphene-based electronic device has proved impervious to neutron irradiation,” according to the company, which emphasises that silicon Hall sensors need radiation-blocking enclosures to operate at such levels.

“Our first set of findings is very promising, and we are expecting more positive outcomes over the next few months,” said NPL scientist Héctor Corte-Leon. “Testing graphene-based electronics is key to demonstrating whether they can be used in harsh environments where, traditionally, their deployment has been limited.”

Alpha, beta and gamma radiation test are to come, as are high-frequency electrical tests to extract small signal parameters and discover what the maximum bandwidth of the devices is, Paragraf told Electronics Weekly.

Amongst its other electrical parameters, the company continued, “normal operating conditions for the sensor are when it is driven by μA of current, leading to μWs of power dissipation. This is low dissipation compared to conventional sensors. Beyond this we have shown the sensor can be driven with as little as 1nA, leading to pW dissipation. This might seem unusual given that most sensors are driven at mA, but the high sensitivity and high electron mobility of the graphene means that we don’t need to do this.”

The tested packaged sensor weighs 0.8g but “could be much lighter”, said Paragraf, which is also investigating the manufacture of other radiation-resistant graphene-based high-rel electronic devices on its large-area graphene deposition process, including devices than make use of the material’s >94% transparency between ~200nm and ~900nm, which peaks at >97% for some wavelengths.

Innovate UK is funding the radiation project. It started in October 2019 and is due to run until the end of 2020.