Charge-carrier injection and extraction at metal-dielectric contact under an applied electric field

There is charge injection/extraction at a metal-dielectric contact. In general, the problem is treated by analogy with that for metal-semiconductor contact. However, the electrical conduction through dielectrics is bulk and electrode limited. Consequently, it is difficult to discriminate between the two effects and to have specific information only about one of the mechanisms. We propose a method that allows to determinate the sign and the value of the electric charge injected/extracted at the metal-dielectric contact. The method is based on the modification of the external electric field of a dielectric when electric charge is injected/extracted onto its surface. The lowest surface charge density measured in the presented experiments was around 1.8 10(-6) cm(-2) which corresponds to a medium distance of about 300 nm between two trapped charges. The Injection/extraction process takes place no matter if there is a conduction current through the sample.