Field Emission of Thermally Grown Carbon Nanostructures on Silicon Carbide

摘要

CNTs are known to be excellent field emitter due to their unique physical and electrical properties. Because of their semi-metallic nature, CNT do not suffer the thermal runaway found in metallic emitters, and their near one-dimension shape make them an ideal emission sources. CNTs growth by thermal decomposition of silicon carbide does not utilize a catalyst, therefore relatively defect free. One drawback to this method, however is that the CNT grow in a very dense carpet. This very dense CNT carpet comes under the affect of field emission screening effects which dampen the field emission. In this thesis, silicon carbide samples are patterned to create elevated emission sites in an attempt to minimize the field emission screening effect. Patterning is accomplished by using standard photolithography methods to implement a masking nickel layer on the silicon carbide. Pillars are created by etching the unmasked area of the silicon carbide in a reactive ion etcher. CNT growth is accomplished in a thermal furnace of varying times based on the selected face of the silicon carbide. Field emission testing to obtain turn-on voltage, field enhancement factor, and current densities is accomplished using a standard vacuum tube diode test configuration, while selected samples are subjected to stability testing over varying times. Although the samples tested did not conclusively demonstrate improved field emission characteristics when compared to values found in the literature for other bundled or pillared CNT, the data collected from similar samples in this work shows that a patterned CNT film can outperform a non-patterned film. From the measured CNT data, the lowest turn-on electric field is found to be 2.5 V/m (taken at 1 A/cm2), and the highest field enhancement factor is of 8007. The variability in performance between samples can be attributed to differences in the emission surfaces as the result of: sample processing; the presence of impurities or amorphous ca.