Technology and characterization of ISFET structures with graphene membrane

Authors: Kinga Kondracka*, Piotr Firek, Piotr Caban, Aleksandra Przewłoka, Jan Szmidt

Graphene due to its properties, such as high sensitivity and biocompatibility finds application in instruments that are used to cooperation with organic substances. At the same time, from the point of view of sensory devices, it is a material with high absorption potential that is able to improve sensitivity and selectivity of these devices. Another benefit of graphene application may be to use its properties in connection with ISFET – Ion Sensitive Field Effect Transistor, which operation principle is based mostly on detection of changes in hydrogen ions concentration.
ISFET transistors ale produced in MOS technology, the difference between them and classic MOSFET (Metal-Oxide-Semiconductor Field Effect Transistor) structures is gate area, where gate metallization was replaced with reference electrode submerged in solution applied in this area. Properties of the solution determine transistor’s action. It is possible to make modifications in gate area of the structure which effects in changes of transistor’s properties. Example of such a modification may be application of graphene layer, which properties may significantly improve detecting capabilities of ISFET devices. For the needs of the research described in this work, graphene was deposited in gate area of transistors through transfer from cooper and germanium surfaces.
To check correctness of ISFETs with graphene layer work, current – voltage characteristics of them were determined. Standard I-V characteristics with SiO2 as gate dielectric were compared with these where gate area was enriched with a graphene layer. Structures with graphene mostly worked properly. Thanks to the results presented in this work, it is possible to carry out further experiments using this structures and organic substances.