Separating different contributions to the shear force in near‐field microscopy

Abstract

SummaryThe shear force between a gold and a graphite sample and an approaching near-field optical probe using tuning fork detection is studied in detail. The adiabatic and dissipative contributions are clearly distinguished by monitoring the amplitude as well as the phase of the tip vibration when approaching the surfaces. Their relative strengths vary differently but characteristically with the distance. The interaction starts in case of graphite at a much larger distance. The adiabatic contribution is larger in the case of gold, whereas graphite shows mostly dissipative interaction. Measurements at various temperatures are performed using a gold sample, showing a dependence of the shear force on the temperature.

Controlling the quality factor of a tuning-fork resonance between 9 and 300 K for scanning-probe microscopy

“…The mechanical resonance is intrinsically stable and the crystal's piezo-electric effect allows for direct electronic interfacing. Quartz tuning forks have proven to be extremely useful as sensors for temperature 1,2 , mass 3 , pressure [4][5][6][7] , and friction [8][9][10][11][12][13][14][15][16][17] . Due to their high mechanical quality factor Q between 10 3 to 10 5 they are very sensitive to environmental changes.…”

Spectroscopy of the shear force interaction in scanning near-field optical microscopy

“…this approach, but little is known about the origin of the involved forces. Some investigations in this field are made under ambient conditions [7][8][9][10] or low temperatures [11][12][13], and only a few under high [14] or ultra-high vacuum (UHV) [15] conditions. In recent years, the fundamental properties of the forces involved in tip-sample interaction were discussed by Refs.…”

“…The electric response corresponds directly to the mechanical oscillation of the tuning fork [11]: m represents the effective mass of the oscillating system, x denotes the lateral displacement of the tip, and o is the driving frequency. The damping constant is DðzÞ ¼ d s ðzÞ þ d t ; and the force constant is KðzÞ ¼ k s ðzÞ þ k t as shown in Fig.…”