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HL: Halbleiterphysik

HL 48: Kohlenstoff/Diamant

HL 48.1: Vortrag

Freitag, 12. März 2004, 11:00–11:15, H17

Diamond based ion-sensitive field effect transitors — •Andreas Härtl, Tobias Heimbeck, Jose Garrido, and Martin Stutzmann — Walter Schottky Institut, Am Coulombwall 3, 85748 Garching

The surface termination of diamond by hydrogen induces a quasi two-dimensional hole accumulation directly at the surface with high carrier concentrations (around 10¹³ cm⁻²) and reasonable mobilities (50 - 100 cm²/ V · s). This unique feature can be used for a novel design of ion-sensitive field effect transistor (ISFET) devices on diamond. The electrolyte is in direct contact with the conductive channel. The species to be detected interact with the surface of the diamond and change the resistance of the hole channel. The sensitivity of these devices is expected to be high due to the proximity of the electrolyte and the conductive channel, in contrast to common silicon based devices, where an insulating layer separates the electrolyte from the conductive channel. Other advantages of diamond are its high degree of biocompatibility as well as its large electrochemical potential window.

We have investigated ISFETs on H-terminated polycrystalline diamond. With the surface completely hydrogenated, no pH-sensitivity was found, whereas partially oxidized devices show pH-sensitivity with values up to 70 mV / pH, exceeding the Nernst limit. Coulombic interaction between surface adsorbates and charge carriers has tentatively been used to explain this behaviour. With a suitable biofunctionalization of the surface, the detection of enzymes, proteins and other biomolecules will be possible.