Miniature Nernstian oxygen sensor for deposition and growth environments

Abstract

A miniature Nernstian-type oxygen sensor employing an ionically conducting stabilized zirconia solid electrolyte and an embedded internal reference electrode is developed and is tested in the temperature range 275-425°C. It is intended for in situ monitoring of oxygen content in deposition and growth environments. Advantages of this sensor are in situ generation of the Ni/NiO two phase internal reference thin film electrode using a solid-state oxygen Coulometric titration technique, its small size ͑5 mmϫ10 mm͒, flat geometry ͑Ͻ1 mm thick͒, relatively low operating temperature, and the fact that the entire sensor can be immersed in the gaseous environment with the unknown oxygen content. The latter feature is distinctly different from commercially available Nernstian oxygen sensors, which employ two-compartment geometries. Depending upon temperature, the time constants for the sensor response to changes in oxygen pressure ranged from seconds to minutes, which is exceptionally fast for these moderately low temperatures. The small thermal mass and size of this single-compartment electrochemical sensor make it suitable for in situ and noninvasive real time monitoring of oxygen content during thin-film deposition or bulk growth of complex oxides.

Improved Internal Reference Oxygen Sensors with Composite Ceramic Electrodes

“…In this study the binary mixture of Ni/NiO is formed in situ after the electrode sintering and sealing procedures by electrochemical reduction of NiO, a procedure introduced by van Setten et al 12 before. By this means the preparation of IRE can start from NiO instead of the mixture of Ni and NiO normally applied, 5,6,11 and the inadvertent oxidation of Ni during cell fabrication is avoided.…”

“…11,12 It is believed that the quite accurate voltage measurements of our cells based on ceramic electrodes can make them good and stably functioning oxygen sensors.…”

“…• C. van Setten et al 12 made planar IROSes using Ni/NiO as the binary mixture. The electrode fabrication and sealing were realized by pulsed laser deposition (PLD).…”

“…[4][5][6] There have been efforts to develop potentiometric oxygen sensors with an internal reference. [4][5][6][7][8][9][10][11][12][13][14] With an internal reference, the cell structure becomes much more compact, which is important to improve mechanical robustness, application adaptability and performance stability of the cell. Haaland, 4 Hetrick et al, 9 Maskell et al 15 and Kaneko et al 16 fabricated pump-gauge devices that consisted of a pump for transmitting oxygen into a small sealed or semi-sealed volume, and a potentiometric gauge for determining the ratio of the pO 2 in the sample gas and in the enclosed volume.…”

Potentiometric Oxygen Sensor with Solid State Reference Electrode

“…D. A key feature of this sensor is the internal oxygen reference electrode made of a suitable metal-metal oxide mixture having sufficient electric conductivity [15]. After sealing the nickel is in a fully oxidized form.…”