Structure Effect Of Field Emission In Nanometer System

In this work, we have made a detailed investigation on field electron emission characteristic of wide band gap semiconductor thin film in nanometer system and the structure effect which has great potential application value in future devices in the corresponding system. On the one hand, we discover the new effects in the known quantum structure; on the other hand, we expect to supply physical model and make theoretical validity for device design based on these quantum structures.1. Effect of the nanometer crystal grain size on field emission performance of wide band gap semiconductor thin film has been studied. The results indicate there has a critical size, only when the crystal grain size is smaller than it, there has the obvious crystal grain size effect to the structure. Namely, with the reduction of crystal grain size, the band gap will increase gradually, and electrons will emit more easily due to the generation of negative electron affinity, which makes the field emission current density enhanced and the threshold field reduced.2. Field emission characteristics of single-layer wide band gap semiconductor thin film structure have been studied. Considering the electronic tunneling effect to potential barrier and the scattering effect during the transport process, we have established a more comprehensive theoretical model of thin film field emission. The results indicate existing obvious thickness effect to the single-layer structure based on a four-step electron emission mechanism. To some kind of semiconductor film material, the field emission performance could be improved remarkably when changing the film thickness in a certain suitable range.3. Field emission characteristics of double-layer wide band gap semiconductor thin film structure have been studied. The results indicate there have two kinds of effects to the double-layer structure: the deposited order effect and the thickness ratio effect. Namely, if the total film thickness is maintained in an invariable situation, changing the order which two kinds of thin films were deposited successively or adjusting their different thickness ratio, then the field emission performance of the double-layer structure will show the remarkable change. All these characteristics indicate that optimizing thin film structure is helpful to improve the field emission performance with great progress and also is advantageous to the device design in the future.