Electrical Behavior in Gas–Solid Interface of Gas Sensors Based on Oxide Semiconductors

A carrier transport for gas adsorption on a gas–solid surface is studied qualitatively. The image force and tunneling effects, which has been applied in metal–semiconductor contact, are included in the space charge model, and the current density is calculated by computer simulation. The number of chemisorbed atom per unit area is calculated to be about 1.42 × 10 ¹² cm ^–2 in a SnO ₂ ‐based gas sensor. The ratio of the current density in CO gas ambient to air is 2.4–10,000 ppm CO gas change. Gas ionic field emission and thermionic field emission for tunneling effect are discussed in heavily doped sensors.