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O: Fachverband Oberflächenphysik
O 90: Semiconductor Substrates
O 90.10: Vortrag
Freitag, 15. März 2013, 12:45–13:00, H45
AlGaN/GaN based pH-sensitive field-effect transistors for nonaqueous solutions — •Johannes Anzt1, Volker Cimalla1, Wilfried Pletschen1, and Oliver Ambacher1,2 — 1Fraunhofer Institute for Applied Solid State Physics, Freiburg, Germany — 2Laboratory for Compound Semiconductor Microsystems, University of Freiburg, Germany
The purpose of this work is to characterize ion-sensitive field effect transistors (ISFETs) based on AlGaN/GaN heterostructures for measurements in nonaqueous solutions. For example, organic solvents offer larger potential windows for electrochemical techniques. Moreover, the pH value in biofuel is an important parameter to characterize quality. While ISFET sensors have already shown excellent sensing properties in aqueous solutions, pH measurements in nonaqueous solutions are faced to several challenging obstacles. Nonaqueous solutions often have low conductivity and the preparation of buffer solutions can be limited by solubility of the constituents. By definition, pH-scales in different solvents or solvent mixtures are not equal, thus, their pH-values (pH = -lg a(H+)) are not comparable. For example, reactivity at pH = 0 in liquid ammonia is by far lower than at pH = 0 in acetic acid. As the pH-ISFET response directly depends on the surface potential, which in turn is directly related to the activity of protons, it offers a possibility to get a universal measuring device with an alternative universal pH-scale.