Évolutions morphologiques des pointes métalliques par traitement thermique (vérification de la théorie de nichols et mullins)

• DOI: 10.1016/0039-6028(71)90256-1
• Publication Date: 2002-10-18T11:23:01Z
• Authors: Vu Thien Binh; A. Piquet; H. Roux; R. Uzan; M. Drechsler
• Keywords: Ligand cone angle; Torr

Abstract The morphological evolution of conical tungsten tips of cone angles between 1 and 15° at temperatures between 1800° and 3000°K is studied inside a scanning electron microscope. The experimental results confirm the theory of Nichols and Mullins: existence of a critical cone angle α = 3°, formation of solid drops for α 3°. For a temperature in the order of 2900 °K (clean surface) the curvature radius at the tip apex increases with time according to the t 1 4 law. For temperatures below 2700°K discrepancies are found, which are due to an evaporation of tungsten compounds produced at the surface by a chemical reaction with the residual gas (10 −5 torr). The measurements at 2900°K have enabled the determination of the surface diffusion coefficient of tungsten: D = 2.4 ×10 6 cm 2 /sec.