Field electron emission experiments with plasma sprayed layers

The paper summarizes the investigation of field electron emission properties of plasma sprayed layers. The tested layers were Cr2O3 + SiO2, Al2O3 + TiO2, TiO2, Cr3C2 + NiCr and Cr3C2 + NiCrAlY. The deposition methods were APS and SPS. The Cr2O3 + SiO2, Al2O3 + TiO2 and TiO2 layers were laser engraved after deposition. Structure investigations of the deposited layers revealed them as composite. The obtained results show, that field electron emission from plasma sprayed layers is comparable with emission from DLC and other carbon-based layers. The best turn-on field was 12 V/μm and has been obtained for laser engraved Al2O3 + 13 wt.% TiO2 layers. Investigation of temperature dependence of emission showed a remarkable influence of hot (Schottky) emission. The emission of Al2O3 + TiO2 layers decreased in elevated temperatures. This has been attributed to the temperature dependence of TiO2 permittivity, which increases with temperature. Computer calculations supported this explanation. The emission parameters suggested very high local electric fields. This probably was the result of field enhancement due to presence of dielectric–conductor–vacuum junction points in addition to that caused by the surface topography.