  Unipolar switching phenomena have attracted a great deal of recent attention,
but the wide distributions of switching voltages still pose major obstacles for
scientific advancement and practical applications. Using NiO capacitors, we
investigated the distributions of the RESET voltage and current. We found that
they scaled with the resistance value Ro in the low resistance state, and that
the scaling exponents varied at Ro = 30 Ohm. We explain these intriguing
scaling behaviors and their crossovers by analogy with percolation theory. We
show that the connectivity of conducting filaments plays a crucial role in the
RESET process.
