Electron-bombarded 〈110〉-oriented tungsten tips for stable tunneling electron emission

Journal Article · Tue Mar 15 04:00:00 EDT 2016 · Review of Scientific Instruments

DOI:https://doi.org/10.1063/1.4943074· OSTI ID:22597084

Yamada, T. K.; Abe, T.; Nazriq, N. M. K.; Irisawa, T. ^[1]

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1. Graduate School of Advanced Integration Science, Chiba University, 1-33 Yayoi-cho, Inage-ku, Chiba 263-8522 (Japan)

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

• OSTI ID: 22597084
• Journal Information: Review of Scientific Instruments, Journal Name: Review of Scientific Instruments Journal Issue: 3 Vol. 87; ISSN 0034-6748; ISSN RSINAK
• Country of Publication: United States
• Language: English

Related Subjects

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND TECHNOLOGY
75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
CAPILLARIES
DIAGRAMS
ELECTRIC FIELDS
ELECTRON BEAMS
ELECTRON EMISSION
ELECTRONS
ETCHING
FIELD EMISSION
GRAIN SIZE
HEATING
ION MICROSCOPY
LAYERS
OXIDES
PARABOLAS
POLYCRYSTALS
SCANNING ELECTRON MICROSCOPY
TUNGSTEN
TUNNEL EFFECT
WIRES
X-RAY DIFFRACTION