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Frequency behaviour of light‐addressable potentiometric sensors
Author(s) -
Werner Carl Frederik,
Wagner Torsten,
Yoshinobu Tatsuo,
Keusgen Michael,
Schöning Michael J.
Publication year - 2013
Publication title -
physica status solidi (a)
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.532
H-Index - 104
eISSN - 1862-6319
pISSN - 1862-6300
DOI - 10.1002/pssa.201200929
Subject(s) - photocurrent , potentiometric sensor , electrical impedance , potentiometric titration , semiconductor , materials science , optoelectronics , focused impedance measurement , dielectric spectroscopy , electrode , chemistry , electrical engineering , electrochemistry , engineering
Light‐addressable potentiometric sensors (LAPS) are semiconductor‐based potentiometric sensors, with the advantage to detect the concentration of a chemical species in a liquid solution above the sensor surface in a spatially resolved manner. The addressing is achieved by a modulated and focused light source illuminating the semiconductor and generating a concentration‐depending photocurrent. This work introduces a LAPS set‐up that is able to monitor the electrical impedance in addition to the photocurrent. The impedance spectra of a LAPS structure, with and without illumination, as well as the frequency behaviour of the LAPS measurement are investigated. The measurements are supported by electrical equivalent circuits to explain the impedance and the LAPS‐frequency behaviour. The work investigates the influence of different parameters on the frequency behaviour of the LAPS. Furthermore, the phase shift of the photocurrent, the influence of the surface potential as well as the changes of the sensor impedance will be discussed.