R. Brunner et al., Influence of environmental conditions on shear-force distance control in near-field optical microscopy, J APPL PHYS, 86(12), 1999, pp. 7100-7106
In our experiments we show, that a contaminating water film is very importa
nt for the shear-force distance control in near-field optical microscopy. T
his is demonstrated at the transition between a hydrophilic glass surface a
nd a hydrophobic Langmuir-Blodgett film of arachidic acid at different rela
tive humidities. This contaminating water film is one, if not the important
reason for the damping of an oscillating fiber during surface approach. It
is further shown, that the bulk viscosity of water alone cannot be respons
ible for the observed damping effect. A thickness dependent viscosity of th
is water film is proposed. These observations can also explain, why the she
ar-force distance control works on nearly all surfaces at ambient condition
s, but fails to work at very low temperatures. (C) 1999 American Institute
of Physics. [S0021-8979(99)00924-X].