Tip preparation for usage in an ultra-low temperature UHV scanning tunneling microscope

Abstract

This work deals with the preparation and characterization of tungsten tips for the use in UHV low-temperature scanning tunneling microscopy and spectroscopy (STM and STS, respectively). These specific environments require in situ facilities for tip conditioning, for further sharpening of the tips, as well as for reliable tip characterization. The implemented conditioning methods include direct resistive annealing, annealing by electron bombardment, and self-sputtering with noble gas ions. Moreover, results from in situ tip characterization by field emission and STM experiments were compared to ex situ scanning electron microscopy. Using the so-prepared tips, high resolution STM images and tunneling spectra were obtained in a temperature range from ambient down to 350 mK, partially with applied magnetic field, on a variety of materials. r

Electron beam collimation with a 40 000 tip metallic double-gate field emitter array and in-situ control of nanotip sharpness distribution

“…In the glow-discharge processing of Spindt single-gate FEAs, 28 the bombardment of neon and hydrogen ions generated by glow-discharge on the FEA decreased B FN but only a small change in A FN resulted. The well-known finishing procedure of etched-wire needle-shape field emitters [44][45][46] is similar to our method in appearance but different in effect: the irradiation of the neon gas ions created by the impact ionization of the field emitted electrons to the emitter tip results in sharpening of the tip down to a few atoms. In contrast, our observation indicates that the neon gas had blunted the sharp tips while at the same time activating non-emitting tips.…”

Scanning tunneling microscopy studies on CeCoIn5 and CeIrIn5

“…An adequate energy resolution (%80 mV) of the STM has been verified by investigating the superconducting gap of Al. We used electrochemically etched tungsten tips which were conditioned in situ by Ne ion sputtering and electron beam annealing [16].…”

Compact device for cleaning scanner-mounted scanning tunneling microscope tips using electron bombardment

“…Above 800 • C, the stable tungsten oxide WO 3 reduces to the more volatile compound WO 2 , which subsequently sublimes. 2,9 Several different parameter sets have been used on mechanically cut Pt-Ir tips to investigate this. One treatment consisted of the following steps: First, the acceleration voltage U a = 950 V was applied.…”