Function and applications of gas sensors

Abstract

Gas sensors directed to high-volume applications are discussed. Mainly semiconductor sensors cover this sector, but the merits of competing devices are shown in comparison. Chemical and physical function is elucidated by spectroscopic results and molecular calculations. Important applications, e.g. monitoring of combustibles, especially methane, and the early detection of fires, are presented as illustrations. Progress in microelectronics has enhanced the development of electronic noses. An early example of such noses, the identification of solvents and also the present state of food aroma detection are described.

Percolation model for a selective response of the resistance of composite semiconductingnpsystems with respect to reducing gases

“…In Schottky approximation, one assumes that the density N − D of mobile electrons in the depletion layer is zero and finds λ n (0) = (2ǫ 0 ǫ r eV s /N D e 2 ) 1/2 by solving the 1D-Poisson equation, where the work function eV s between the surface and the core is of the order of 1 eV or somehow below [15]. Here, we will rely to the values of λ n (0) ≈ 10 nm and N D = 3.5 · 10 −3 nm −3 that have already been used in [3,5,9,19,20]. From λ n (0) and N D , one gets the surface density of the (initially) adsorbed oxygen by the condition of "charge neutrality" as N 0 ox,n ≈ λ n (0)N D = 3.5 · 10 −2 nm −2 .…”

Nano-Porous Silicon-Based Mini Hydrogen Fuel Cells

“…Concerning the operating principle of the Au/PS/Si sensor to detect the CO molecules, one can suppose that at the first stage, the water molecules from the humid air in the presence of the Au catalyst interact with the CO, resulting in the formation of hydrogen, according to the electrode reaction (Kohl, 2001) CO + H 2 O → CO 2 + H 2 (23)…”

Complementary Metal Oxide Semiconductors Microelectromechanical Systems Integration

“…Conventional metal oxide gas sensors, which are mostly aluminia substrate-based, are commonly used for sensing inflammable hydrocarbon gases 28 (like CH 4 ) and other toxic gas 29 (like CO). However, these suffer from the two principal limitations, viz., (a) their relatively high operating temperature 30 (³ 300 °C) and (b) large power dissipation 31 (0.5-1 W). Both these features are unacceptable for continuous gas monitoring in many environmental scenario, such as underground coal mines.…”