Investigation of the time evolution of STM-tip temperature during electron bombardment

Abstract

In the field of scanning probe microscopy, great attention must be paid to the state of sample and probe with respect to unintentionally adsorbed molecules. There are many techniques for cleaning tips described in literature, among them the use of accelerated electrons as an energy source. So far, all of the setups described yielded either no or only indirect information about the probe's temperature reached during the cleaning procedure. The Near-Field Scanning Thermal Microscopy probe not only serves as scanning tunneling microscope tip, but also includes a thermosensor in the vicinity of the probe's apex. Since the tip's body mainly consists of glass, which has a softening point of 1100 K, it must not be heated excessively in order to prevent its destruction. The authors use electron bombardment for cleaning these unique sensors, while the thermosensor is used as feedback for an automated device which is controlling the procedure. Our findings reveal that probe temperatures of up to 1220 K can be reached for short periods of time without causing any damage. In this article, the authors describe the device as well as experimental data concerning the relation between the energies used for cleaning and the resulting temperature of the probe. The presented data might serve as an indicator for other setups where a direct measurement of the temperature of the apex is impossible.