  It is well known that residual electrostatic forces create significant
difficulties to precise measurements of the Casimir force and to wide use of
Casimir-operated microdevices. We experimentally demonstrate that with the help
of Ar-ion cleaning of the surfaces it is possible to make electrostatic effects
negligibly small as compared to the Casimir interaction. Our experimental setup
consists of the dynamic atomic force microscope supplemented with an Ar-ion gun
and argon reservoir. The residual potential difference between the Au-coated
surfaces of a sphere and a plate was measured both before and after the in situ
Ar-ion cleaning. It is shown that this cleaning decreases the magnitude of the
residual potential by up to an order of magnitude and makes it almost
independent on separation. The gradient of the Casimir force was measured using
ordinary samples subjected to the Ar-ion cleaning. The obtained results are
shown to be in good agreement with both previous precision measurements using
the specially selected samples and with theoretical predictions of the Lifshitz
theory. The conclusion is made that the suggested method of in situ Ar-ion
cleaning is effective in reducing the electrostatic effects and therefore is a
great resource for experiments on measuring the Casimir interaction and for
Casimir-operated microdevices.
