Temperature influence and hot electrons in field electron emission from composite layers deposited by air plasma spraying of powders and suspensions

A temperature dependence of field electron emission from composite layers has been investigated. Air plasma spraying associated with laser engraving and suspension plasma spraying has been used for preparation of composite field electron emitters. The deposited materials were fine sized Ti O 2 and Ti O 2 ∕ Al 2 O 3 powders. The sprayed titanium oxide layers contained rutile, anatase, and Magneli phases as well as alumina and alumina-titania spinel. Field emission from these layers was strongly influenced by the emitter temperature. A decrease of emission with temperature rise was observed. This effect has been explained as a result of rutile grain permittivity and conductivity increase with temperature. Model calculations supported this explanation. The plots of low-level current emission as a function of temperature have been used for identification of emission mechanism in this range. The presence of low-current tail in Fowler-Nordheim plot has been attributed to hot electrons. An absence of such tail should indicate a metal-like conduction mechanism in the emitting layer. As the penetration of external electric field into the bulk of emitter material creates conditions for generation of hot electrons, the temperature dependence of electron emission current may be used for indication of carrier transport mechanism in the composite layers.