Application of Focused Ion Beam Techniques to the Fabrication of Lateral-Type Thin-Film Edge Field Emitters

Abstract

Focused ion beam (FIB) techniques were applied to the fabrication of lateral-type thin-film edge field emitters (FE's). In the present paper, two different processes to fabricate lateral-type thin-film edge FE's have been demonstrated. One technique utilizes the FIB as an etching tool. The FIB with a diameter of 1 µm was used to cut a thin nickel film with a thickness of 150 nm deposited on a silicon substrate which had been thermally oxidized, in order to produce an emitter-collector gap. As a result, a diode structure with the gap of about 2 µm could be obtained. In the other technique, a tungsten oxide thin film was exposed with the FIB to form the electrodes, followed by development in sodium hydroxide solution and reduction in hydrogen ambient. The FIB with a diameter of 5 µm was used to expose the tungsten oxide, a negative resist against ion beam irradiation, with a thickness of 40 nm. A diode structure with the gap of also about 2 µm could be obtained. Current-voltage characteristics of these devices were measured and field emission currents were observed. Ejection of the electrons from the latter FE into vacuum was confirmed with luminescence of zinc sulfide phosphor.