Tungsten Oxide Charge Layer

Tungsten oxide charge layer structure of the surface atomic arrangement will be periodically destroyed. The tungsten oxide charge layer surface contains more dangling bonds, and each dangling bond in the tungsten oxide charge layer corresponds to a surface level.

Many surface energy levels will form the surface energy band. Due to the presence of dangling bonds, the band near the surface of the tungsten oxide charge layer will be bent. If the surface energy level is the acceptor level, electrons can be captured from the material body. As a result, the surface of the material appears negative potential, which will cause some repulsion, which will hinder the continuous drift of electrons inside the tungsten oxide. The final will be to achieve electrical balance.

When tungsten oxide is in equilibrium, the surface is negatively charged and the inside is positively charged. The band will bend upward to form a space charge zone. At the same time, tungsten oxide layer surface of the accumulation of electrons will occur. If the surface energy level is the donor level, the surface energy band will bend downward. At the same time, the electrons on the surface of the charge layer will be depleted, resulting in an inversion layer.

Therefore, when the tungsten oxide is in contact with the gas to be measured, the gas molecules to be tested will interact with the atoms on the surface of the tungsten oxide charge layer. Thus, realizing the exchange of electrons, resulting in the change of the number of carriers in the space charge region. And then change the resistance or conductivity of tungsten oxide, the goal of detecting gas concentration, composition. If the measured gas is an electrophilic oxidizing gas, the electrons in the tungsten oxide conduction band are easily trapped by the measured gas. Thereby reducing the electron concentration on the surface of the tungsten oxide charge layer, resulting in an increase in the electrical resistance of the tungsten oxide. If the measured gas is a reducing gas, it will eventually lead to a decrease in the electrical resistance of the tungsten oxide.

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