  Electric conduction in thin graphite film was tuned by two gate electrodes to
clarify how the gate electric field induces electric carriers in thin graphite.
The graphite was sandwiched between two gate electrodes arranged in a top and
bottom gate configuration. A scan of the top gate voltage generates a
resistance peak in ambiploar response. The ambipolar peak is shifted by the
bottom gate voltage, where the shift rate depends on the graphite thickness.
The thickness-dependent peak shift was clarified in terms of the inter-layer
screening length to the electric field in the double-gated graphite film. The
screening length of 1.2 nm was experimentally obtained.
