Field emission study on ultrathin aluminum nitride coated molybdenum emitters (Ultrathin films)

Electron emission characteristics of Mo tips coated with a Wide Band Gap Material (WBGM), AlN, were studied in this dissertation. In situ I-V measurements and Transmission Electron Microscopy (TEM) are used to obtain reliable electron emission data and precise characterization of the coating material. AlN deposition and I-V measurements from AlN coated Mo tips were performed sequentially in the same chamber.; This study is divided into four major parts: coating thickness, surface treatments, maximum current output, and emission stability. Since the in situ I-V measurement system allows a sequential change in the coating thickness in the chamber, thickness effects on the electron emission were investigated. Anomalous coating thickness dependence was found in the Mo emitter coated with ultra thin AlN (<20 nm). For the emitter coated with a thin AlN layer (<10 nm), threshold voltages increased with the increase in the coating thickness.; The effects of the AlN emitter's surface conditions were investigated through the modification of surface conditions with different plasma treatments and an ultra-thin metal deposition on the emitter. Significant suppression of the electron emission was observed in the emitter treated with an oxygen plasma. On the other hand, nitrogen and hydrogen plasma treatments did not affect the electron emission characteristics, which is different from the results of diamonds.; The third main experiment of this study was on the maximum current output from the emitters. Bare Mo tips showed approximately 1–10 μA. However, the Mo tip coated with ultra-thin AlN (<20 nm) emitted 52 μA before it failed.; Emission stability was studied with the incorporation of the plasma treatments on the emitters. Short-term change is predominant in AlN coated Mo tips. The noises from the emitters were studied with perspective to the local work function change due to the dynamic motions of the adsorbed atoms.; AlN coating results in a change in the electron emission from the Mo tip. The electron emission from the AlN coated Mo tips showed two characteristic regions, shallow and steep. Space charge in the AlN coating layer id suggested as the cause the shallow and sharp transitions in the emitter.; An electron emission mechanism is proposed in order to explain the anomalous thickness dependence of the electron emission from the Mo tip coated with the AlN. The proposed emission model incorporates impact ionization of the AlN layer into the field emission process. Before the impact ionization (<10 mn of the AlN coating) occurs, no electron enhancement was observed. (Abstract shortened by UMI.)...