SHARPENING PROCESSES OF SCANNING-TUNNELING-MICROSCOPY SCANNING TUNNELING SPECTROSCOPY TIPS BY THERMAL FIELD TREATMENT

In order to prepare a scanning tip suitable for scanning tunneling mic roscopy (STM)/scanning tunneling spectroscopy (STS) operated in ultrah igh vacuum (UHV) with a reproducible and ideal profile of the [111]-or iented W tip, sharpening and cleaning treatments were carried out by h eating the tip while applying high voltage in UHV (thermal field (T-F) treatment). The treated tips were evaluated by field emission microsc opy (FEM). The appropriate values to build up the W tip along the [111 ] axis for a treatment parameter, \VT-F/V-base\, range from 2 to 2.6 u nder fixed conditions of tip heating temperature and time of about 130 0 K and 60 s, respectively. It has been also realized that the formati on of an ideal tip completely surrounded by three {112} facets at its apex requires a successive heat treatment: an initial T-F treatment, s imple heating at about 1000 K to develop the {112} facets, and a final T-F treatment.