Field Emission Properties of Metallic Nanowires Grown in Polymer Ion-track Membranes

摘要

We have measured the field emission (FE) properties of randomly distributed free-standing Cu and Ni nanowires on thin metallic substrates of some mm{sup}2 size. The wires were grown in the etched ion-tracked pores of polycarbonate membranes [1] with various diameters of 120-330 nm, lengths of 8-18μm and number densities of 10{sup}6-10{sup}8 emitters/cm{sup}2. In Fig. 1 a typical sample surface with well-aligned Ni nanowires is shown. The emission site density and current distribution of the nanowire cathodes were measured with the field emission scanning microscope (FESM) at about 10{sup}(-7) Pa [2]. All samples showed similar onset fields for 1 nA of some V/μm but rather different emission uniformity. At 5 V/μm the free standing Cu and Ni nanowires provided less than 4×10{sup}4 emitters/cm{sup}2, while the bundled Cu [1] and Au-coated Ni nanowires (Fig. 2) yielded more than 10{sup}5 emitters/cm{sup}2. For the latter sample about 1.6×10{sup}6 emitters/cm{sup}2 were found at 18 V/μm, i.e. about than 10% of the nanowires emitted.