Electron-bombarded ⟨110⟩-oriented tungsten tips for stable tunneling electron emission.

摘要: A clean tungsten (W) tip apex with a robust atomic plane is required for producing stable tunneling electron emission under strong electric fields. Because fabricated from wire by aqueous chemical etching covered impurity layers, heating treatment in ultra-high vacuum experimentally known to be necessary. However, frequently melts the and causes unstable emissions. We investigated quantitatively found useful method prepare emissions controlling electron-bombardment power. Careful characterizations of structures were performed combinations using field I-V curves, scanning microscopy, X-ray diffraction (transmitted Debye-Scherrer Laue) micro-parabola capillary, ion microscopy. Tips chemically etched (1) polycrystalline W wires (grain size ∼1000 nm) (2) long-time heated larger than 1 mm). Heating 10-40 (10 s) was good enough remove oxide layers produced emission; however, around 60 threshold power increase radius, typically +10 ± 5 nm (onset melting). Further, grain necessary obtain conical shape apex.