Electronic characterization of thin diamondlike carbon films for pH sensor applications

Frank Schitthelm; Kai-Sven Roever; Ruediger Ferretti

doi:10.1117/12.333742

18 December 1998 Electronic characterization of thin diamondlike carbon films for pH sensor applications

Frank Schitthelm, Kai-Sven Roever, Ruediger Ferretti

Proceedings Volume 3539, Chemical Microsensors and Applications; (1998) https://doi.org/10.1117/12.333742
Event: Photonics East (ISAM, VVDC, IEMB), 1998, Boston, MA, United States

Abstract

Amorphous Diamond like carbon (DLC) thin films were deposited on to 4'-silicon wafers by an electron cyclotron resonance microwave excited methan (CH₄) or ethin (C₂H₂) plasma at low pressure. Electronic characterization of DLC films were performed by I/V and C/V measurements using MIS-structures. Whereas the electrochemical pH-characteristics were measured using ion- sensitive field-effect transistors. It is shown, that the type of carrier transport mechanism in DLC films depends on the process conditions and that the electrical conductivity varies over a wide range. This can be adjusted mainly by the kinetic energy of the C_xH_x⁺ ions and the C to H ratio, which depends on the type of process gas. The dominant charge transport mechanism in DLC films based on a methan plasma is the Poole-Frenkel emission whereas the charge flow for ethin based DLC films is space-charged limited. The electronic conductivity of DLC films deposited with ethin as process gas is typically about five orders of magnitude higher than methan based films. The electrochemical characterization shows a pH-sensitivity in the range of 50 - 57 mV/pH and a long-term pH signal stability in the range of 0.3 - 25 (mu) V/h. Based on the different pH-sensitivities int will be possible to produce a pH-sensor in differential mode using DLC/DLC or DLC/Ta₂O₅ combinations for the sensitive layers.

Citation Download Citation

Frank Schitthelm, Kai-Sven Roever, and Ruediger Ferretti "Electronic characterization of thin diamondlike carbon films for pH sensor applications", Proc. SPIE 3539, Chemical Microsensors and Applications, (18 December 1998); https://doi.org/10.1117/12.333742

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