  The experimental investigation of the Casimir force between a large
metallized sphere and semiconductor plate is performed using an atomic force
microscope. Improved calibration and measurement procedures permitted reduction
in the role of different uncertainties. Rigorous statistical procedures are
applied for the analysis of random, systematic and total experimental errors at
95% confidence. The theoretical Casimir force is computed for semiconductor
plates with different conductivity properties taking into account all
theoretical uncertainties discussed in literature. The comparison between
experiment and theory is done at both 95 and 70% confidence. It is demonstrated
that the theoretical results computed for the semiconductor plate used in
experiment are consistent with data. At the same time, theory describing a
dielectric plate is excluded by experiment at 70% confidence. Thus, the Casimir
force is proved to be sensitive to the conductivity properties of
semiconductors.
