Preparation of scanning tunneling microscopy tips using pulsed alternating current etching

Abstract

ThLf sec1ionLf imendedfor 1he fJuhlication of ( I ) An electrochemical method using pulsed alternating current etching (PACE) to produce atomically sharp scanning tunneling microscopy (STM) tips is presented. An Arduino Uno microcontroller was used to control the number and duration of the alternating current (AC) pulses, allowing for ready optimization of the procedures for both Pt:lr and W tips using a single apparatus. W tips prepared using constant and pulsed AC power were compared. Tips fashioned using PACE were sharper than those etched with continuous AC power alone. Pt:lr tips were prepared with an initial coarse etching stage using continuous AC power followed by fine etching using PACE. The number and potential of the finishing AC pulses was varied and scanning electron microscope imaging was used to compare the results. Finally, tip quality using the optimized procedures was verified by UHY-STM imaging. With PACE, at least 70% of the W tips and 80% of the Pt:lr tips were of sufficiently high quality to obtain atomically resolved images of HOPG or Ni(l 11 ).

Formation of surface oxides and Ag2O thin films with atomic oxygen on Ag(111)

“…The experimental apparatus and approach has been described in previous publications [32,33], and further detail is provided in the supporting information. AO was generated by dissociating O 2 over a hot Ir filament [34] over the front face of the Ag(111) crystal.…”

Electrochemical etching of lightweight nanotips for high quality‐factor quartz tuning fork force sensor: atomic force microscopy applications

“…For sensor fabrication a nanotip is attached to the apex of a tine of the QTF and nanotips are usually fabricated by electrochemical etching of metallic wires, e.g. Pr‐Ir [14], iron‐based alloys [15], platinum [16], gold [17], rhodium, palladium [18], silver [19], copper, nickel [20] and tungsten [21, 22]. Several properties such as high mechanical strength, durability, high conductivity (for scanning tunnelling, field‐ion microscopy and Kelvin probe microscopy) and reliability are important for the nanotips.…”

“…First, one end of the wire is coated and etched with a trapezoidal signal. The coating hinders the effect of the fast etching at the lower end [21], thus the wire between air–electrolyte interface and coated region is etched into a long slender micro‐needle. In the second step, the wire is elevated to a suitable height using a precision microstage of the custom designed etching setup and DC etching is performed to form a very sharp tip apex.…”

“…However, shaft size of the DC etched nanotips is large and massive. On the other hand, several dynamic etching techniques are explored [21][22][23][24][25]. Ju et al [24] proposed a method to dynamically control the neck-in position of a tungsten wire to fabricate nanotips with desirable lengths.…”

Robust procedure for creating and characterizing the atomic structure of scanning tunneling microscope tips

“…However, a well defined tip structure at the atomic scale is still hard to achieve. Mechanical grinding [1], electro-polishing [11] or electrochemical etching [12–13] are standard ex situ methods for preparing microscopically sharp tips. The tip apex can be cleaned in situ using, e.g., Ar ion sputtering or electron bombardment [14], but this may disrupt the crystalline structure, which cannot be repaired by annealing since this will yield a blunt tip.…”