Secondary electron emission behavior of nanostructured fluorocarbon film

Abstract

Based on the theoretical analysis of secondary electron emission (SEE) behavior of semiconductor and insulator, this paper numerically calculates electron affinity (EA) and energy difference between the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) of fluorocarbon (FC) films with the variation of fluorine to carbon (F/C) ratio. As fluorine element exhibits strong electronegativity, the LUMO energy decreases and the EA increases with the incremental content of fluorine. Increasing F/C ratio contributes to stronger electron capture capacity. SEE behavior is mainly affected by the chemical compositions and island-like nanostructure of FC films. Based on the dynamic scaling theory, the growth process is divided into two stages, in which roughening and smoothing effects play the dominant role, respectively. Growth index of the two stages are 0.57±0.01 and 0.10±0.01. Prolonging sputtering time contributes to higher film thickness, bigger surface roughness and larger F/C ratio. Experimental results confirm that secondary electron emission yield (SEY) decreases from 3.02 to 1.60, as film thickness increases from 19 to 113 nm. After 7 days and 60 days aging, the highest incremental δmax is 3.68% and the largest reduced E1 is 11.11%. The SEE behavior of FC film is relatively stable in the atmosphere.