Tum-on field

A new trend emerged. The production of intentionally diverse composite carbon films, rich in a variety of graphitic nanostructures, became commonplace. These films contained wide assortments of naturally occurring carbonaceous nanostructures, including but certainly not limited to carbon particles, onions, clusters, fullerenes, nanotubes, and nanofibers. These nanostructured carbon films performed significantly better than both the planar carbon and Spindt metallic emitters with tum-on fields as low as l-5V/pm. Moreover, it was determined that carbon has one of the lowest sputter coefficients [287], making its allotropes extremely stable when bombarded by positive ions associated with local liberated ionized gas species. 

In the following years, several experimental and theoretical studies on the FE properties of CNTs were performed [17-21]. These were mainly conducted using isolated [16,22], fiber-Uke [23,24], arrayed [25-30], and film-Uke CNTs [31-37]. In comparison with traditional metallic anitters, the merits of CNTs as a field anitler can be summarized as (1) low tum-on field (FJ or threshold field (Efl,), (2) enhanced FE current, (3) high field enhancanent factor, and (4) good FE stability. 

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