Metal film resistance temperature coefficient of resistance varies with film thickness, thin films are negative, thick films are positive, and thicker films are similar but not identical to bulk materials. In general, the resistance temperature coefficient of resistance changes from negative to positive as the film thickness increases to tens of nanometers.
In addition, the evaporation rate also affects the resistive temperature coefficient of metal films. Low evaporation rate prepared by the film layer is loose, the electrons across its potential barrier and the ability to produce conductivity is weak, coupled with oxidation and adsorption, so the resistance value is high, the resistance temperature coefficient is small, or even negative, with the increase in the evaporation rate, the resistance temperature coefficient of the resistance of a small change from large, from negative to positive. This is due to the low evaporation rate of the film prepared due to the oxidation of the semiconductor properties, resistance temperature coefficient of negative values. The films prepared at high evaporation rate tend to have metallic properties and have a positive resistance temperature coefficient.
Since the structure of the film changes irreversibly with temperature, the resistance and resistance temperature coefficient of the film also change with the temperature of the coating layer during evaporation, and the thinner the film, the more drastic the change. This can be thought of as a result of the chemical changes caused by re-evaporation and redistribution of particles of the approximate island or tubular structure film on the substrate, as well as lattice scattering, impurity scattering, scattering of lattice defects, and oxidation.
–This article is released by vacuum coating machine manufacturer Guangdong Zhenhua
Post time: Jan-18-2024