New Method for Preparing Unusually Oriented Tungsten Tips and Their Growth Mechanism

Abstract
A new method for preparing tungsten tips having an unusual orientation, for example, the [100]- or the [111]-orientation, was studied by using a field emission microscope. It was found that tungsten tips having the [100]- or the [111]-orientation could be obtained with heat treatment of the tip at low temperature (1500°–2300°K) after introducing air or oxygen into the experimental tube. To make clear the mechanism of the change in the tip orientation from the normal orientation to the unusual one, light- and electron-microscopic observations of the cathodes were carried out. As a result, it became clear that the growth mechanism of the unusual tip could be explained by assuming that the tungsten tip rotated around a fixed -axis under the tungsten carbide film so as to transfer to the stable state from a semi-stable state.

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