Berlin 2005 – scientific programme
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AKB: Biologische Physik
AKB 85: Biosensors and Biohybrid Systems
AKB 85.4: Talk
Wednesday, March 9, 2005, 13:15–13:30, TU H2013
Characterization of a chemically passivated GaAs based sensor device in electrolytes — •Sebastian M. Luber1, Daniel Gassull2, Dieter Schuh1, Motomu Tanaka2, Marc Tornow1, and Gerhard Abstreiter1 — 1Walter Schottky Institut, TU München, 85748 Garching, Germany — 2Lehrstuhl für Biophysik, E22, TU München, 85748 Garching, Germany
Functionalized field effect devices are promising candidates to act as smart substrates for sensor applications. For a use in biological systems an intermediate layer has to provide stabilization against electrochemical decomposition, and allow effective electrostatic coupling of the surface potential to the conductive channel.
We present a resistor device passivated with a 4’-substituted 4-mercaptobiphenyl self-assembled monolayer (SAM) for sensing applications. Starting material was a GaAs-AlGaAs heterostructure containing a quasi 2D electron gas 60nm beneath the surface. In the first part of our study we tested the stability of the device against aqueous solutions. Whereas a bare GaAs device degraded rapidly the coated samples showed a remarkable increase in stability. In the second part samples coated with monolayers with CH3 (MBP-CH3) and OH (MBP-OH) substituents in various buffered electrolyte solutions were characterized. For the MBP-OH coated sample, a change in pH induced a change in the resistance of the device. This behaviour can be expected due to non-specific adsorption at the hydrophilic surface of the −OH terminated SAM. However unexpectedly, the sample grafted with a MBP-CH3 SAM with a hydrophobic surface also showed a clear response on pH.