  We elucidate on the low mobility and charge traps of the chemically reduced
graphene oxide (RGO) sheets by measuring and analyzing temperature dependent
current-voltage characteristics. The RGO sheets were assembled between source
and drain electrodes via dielectrophoresis. At low bias voltage the conduction
is Ohmic while at high bias voltage and low temperatures the conduction becomes
space charge limited with an exponential distribution of traps. We estimate an
average trap density of 1.75x10^16 cm^-3. Quantitative information about charge
traps will help develop optimization strategies of passivating defects in order
to fabricate high quality solution processed graphene devices.
