pH-sensitive WO/sub 3/-based microelectrochemical transistors
Electrochemical properties of an array of closely spaced (1.2 ..mu..m) Au or Pt microelectrodes (approx.2 ..mu..m wide x approx.50 ..mu..m long x 0.1 ..mu..m high) coated by a 0.15-..mu..m-thick layer of polycrystalline WO/sub 3/ are reported. The WO/sub 3/ is deposited on the electrodes by radio frequency (rf) sputtering of a WO/sub 3/ target. The cyclic voltammetry of these microelectrodes indicates that WO/sub 3/ connects individual microelectrodes. The change in resistance of WO/sub 3/ connecting two microelectrodes as a function of electrochemical potential spans 4 orders of magnitude, from approx.10/sup 6/ to approx.10/sup 2/ ohm. A pair of WO/sub 3/-connected microelectrodes functions as a microelectrochemical transistor that is sensitive to pH. The maximum slope of the drain current, I/sub D/, vs. gate voltage, V/sub G/, plot at fixed drain voltage, V/sub D/, gives a transconductance of 12 mS/mm of gate width. Operating at a frequency of 1 Hz, the power amplification by the WO/sub 3/-based transistor is 200, at pH 1. The power amplification decrease at both higher pH and higher frequency. The properties of the WO/sub 3/-based microelectrochemical transistor allow its use as a real-time pH sensor: a reproducible change in I/sub D/, at fixed V/sub G/ and V/sub D/, is obtained rapidly as the pH of a stream flowed continuously past the electrode is repetitively changed from pH 3.9 to pH 7.2.
- Research Organization:
- Massachusetts Institute of Technology, Cambridge
- OSTI ID:
- 6871692
- Journal Information:
- J. Phys. Chem.; (United States), Journal Name: J. Phys. Chem.; (United States) Vol. 91:3; ISSN JPCHA
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
400400* -- Electrochemistry
CHALCOGENIDES
CHEMISTRY
DATA
ELECTRIC CONDUCTIVITY
ELECTRICAL PROPERTIES
ELECTROCHEMISTRY
ELECTRODES
ELEMENTS
EXPERIMENTAL DATA
GOLD
INFORMATION
METALS
NUMERICAL DATA
OXIDES
OXYGEN COMPOUNDS
PH VALUE
PHYSICAL PROPERTIES
PLATINUM
PLATINUM METALS
REFRACTORY METAL COMPOUNDS
SEMICONDUCTOR DEVICES
TRANSISTORS
TRANSITION ELEMENT COMPOUNDS
TRANSITION ELEMENTS
TUNGSTEN COMPOUNDS
TUNGSTEN OXIDES
VOLTAMETRY