Researchers have made graphene field effect transistors (GFETs) with the lowest normalized 1/f noise parameter to date, demonstrating their use as sulfate ion sensors with a record resolution.

GFETs are particularly well suited as sensors due to the high achievable gain and extreme sensitivity to the external environment due to the atomic thickness of graphene. Even early work on graphene sensors demonstrated detection of single gas molecules colliding with the graphene surface. Although a wide variety of GFET sensors have been demonstrated, including sensing of molecules in the gas phase, alkali atoms in high vacuum, ions in an aqueous environment and biomolecules in physiological solutions, disproportionately little attention has been given to sensors with an optimized signal-to-noise ratio (SNR), which is required for quantitative analysis.

The research team from Canada and Spain noted the scaling of 1/f noise in graphene with the GFET active area and measured the noise across a range of GFET sizes. For the largest size sensor, with area 5.12 mm x 5.12 mm, a record-breaking 1/f noise of 5x10^-13 was observed. To demonstrate the use of such low noise GFETs, the researchers detected sulfate ions with a limit of detection below 1x10^-5 M. The resolution is more than 16 times improved over state of the art silicon FET sensors targeting monovalent species, and more than 80 times over that of other sulfate FET sensors. The research was published in the journal Nanotechnology.

While the size scaling applies to all FETs, the researchers note that their findings are particularly pertinent for GFETs, because of the simple fabrication procedure for synthesis of large area GFETs compared to those made of conventional semiconductors. The discovery is good news for users of graphene-based sensors, which are readily made in large batches and are already being employed in a wide range of areas including medical treatment, environmental surveys, food control, forensics and research.

Graphenea offers standard GFET products with a Hall-bar or 2-probe geometry for use in sensing, with custom designs also available.