In order to prepare a scanning tip suitable for scanning tunneling microscopy (STM)/scanning tunneling spectroscopy (STS) operated in ultrahigh vacuum (UHV) with a reproducible and ideal profile of the [111]-oriented W tip, sharpening and cleaning treatments were carried out by heating the tip while applying high voltage in UHV (thermal field (T-F) treatment). The treated tips were evaluated by field emission microscopy (FEM). The appropriate values to build up the W tip along the [111] axis for a treatment parameter, |V
T-F/V
base|, range from 2 to 2.6 under fixed conditions of tip heating temperature and time of about 1300 K and 60 s, respectively. It has been also realized that the formation of an ideal tip completely surrounded by three {112} facets at its apex requires a successive heat treatment: an initial T-F treatment, simple heating at about 1000 K to develop the {112} facets, and a final T-F treatment.
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