Graphene Transistors Are Insensitive to pH Changes in Solution

• Published in: Nano letters Vol. 11; no. 9; pp. 3597 - 3600
• Main Authors: Fu, Wangyang, Nef, Cornelia, Knopfmacher, Oren, Tarasov, Alexey, Weiss, Markus, Calame, Michel, Schönenberger, Christian
• Format: Journal Article
• Language: English
• Published: Washington, DC American Chemical Society 14-09-2011
• Subjects: Aluminum; Aluminum Oxide - chemistry; Applied sciences; Aqueous electrolytes; Biosensing Techniques - methods; Buffers; Cleaning; Copper - chemistry; Cross-disciplinary physics: materials science; rheology; Electrochemistry - methods; Electrodes; Electronics; Exact sciences and technology; Fluorobenzenes - chemistry; Fullerenes and related materials; diamonds, graphite; Graphene; Graphite - chemistry; Hydrogen-Ion Concentration; Ions; Materials science; Nanoparticles - chemistry; Nanotechnology - methods; Optics and Photonics - methods; Physics; Semiconductor devices; Semiconductor electronics. Microelectronics. Optoelectronics. Solid state devices; Specific materials; Temperature; Thin films; Transistors; ion-sensitive FET (ISFET); Graphene; field-effect transistor (FET); pH value; Oxide layer; Experimental design; Field effect transistors; Gallium tellurides; Electrolytes; Chemical potential; Silicon; Gates
• ISSN: 1530-6984; 1530-6992
• DOI: 10.1021/nl201332c

We observe very small gate-voltage shifts in the transfer characteristic of as-prepared graphene field-effect transistors (GFETs) when the pH of the buffer is changed. This observation is in strong contrast to Si-based ion-sensitive FETs. The low gate-shift of a GFET can be further reduced if the graphene surface is covered with a hydrophobic fluorobenzene layer. If a thin Al-oxide layer is applied instead, the opposite happens. This suggests that clean graphene does not sense the chemical potential of protons. A GFET can therefore be used as a reference electrode in an aqueous electrolyte. Our finding sheds light on the large variety of pH-induced gate shifts that have been published for GFETs in the recent literature.