Large area graphene ion sensitive field effect transistors with tantalum pentoxide sensing layers for pH measurement at the Nernstian limit

Journal Article · Mon Aug 25 04:00:00 EDT 2014 · Applied Physics Letters

DOI:https://doi.org/10.1063/1.4894078· OSTI ID:22310964

Fakih, Ibrahim; Sabri, Shadi; Szkopek, Thomas ^[1]; Mahvash, Farzaneh ^[1]; Nannini, Matthieu ^[2]; Siaj, Mohamed ^[3]

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1. Department of Electrical and Computer Engineering, McGill University, Montreal, Quebec H3A 2A7 (Canada)
2. McGill Nanotools Microfab, McGill University, Montreal, Quebec H3A 2A7 (Canada)
3. Département de Chimie et Biochimie, Universite du Québec à Montréal, Montreal, Quebec H3C 3P8 (Canada)

We have fabricated and characterized large area graphene ion sensitive field effect transistors (ISFETs) with tantalum pentoxide sensing layers and demonstrated pH sensitivities approaching the Nernstian limit. Low temperature atomic layer deposition was used to deposit tantalum pentoxide atop large area graphene ISFETs. The charge neutrality point of graphene, inferred from quantum capacitance or channel conductance, was used to monitor surface potential in the presence of an electrolyte with varying pH. Bare graphene ISFETs exhibit negligible response, while graphene ISFETs with tantalum pentoxide sensing layers show increased sensitivity reaching up to 55 mV/pH over pH 3 through pH 8. Applying the Bergveld model, which accounts for site binding and a Guoy-Chapman-Stern picture of the surface-electrolyte interface, the increased pH sensitivity can be attributed to an increased buffer capacity reaching up to 10{sup 14} sites/cm{sup 2}. ISFET response was found to be stable to better than 0.05 pH units over the course of two weeks.

• OSTI ID: 22310964
• Journal Information: Applied Physics Letters, Journal Name: Applied Physics Letters Journal Issue: 8 Vol. 105; ISSN APPLAB; ISSN 0003-6951
• Country of Publication: United States
• Language: English

Related Subjects

75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
CAPACITANCE
CAPACITY
ELECTROLYTES
FIELD EFFECT TRANSISTORS
GRAPHENE
INTERFACES
LAYERS
SENSITIVITY
SURFACE POTENTIAL
SURFACES
TANTALUM OXIDES