We systematically investigated plasma-based chlorination of graphene and compared its properties before and after such treatment. X-ray photoelectron spectroscopy revealed that a high Cl coverage of 45.3% (close to C2Cl), together with a high mobility of 1535 cm(2)/(V s), was achieved. The C:Cl ratio n (CnCl) can be effectively tuned by controlling the dc bias and treatment time in the plasma chamber. Chlorinated graphene field-effect transistors were fabricated, and subsequent Hall-effect measurements showed that the hole carrier concentration in the chlorinated graphene can be increased roughly by a factor of 3. Raman spectra indicated that the bonding type between Cl and graphene depends sensitively on the dc bias applied in the plasma chamber during chlorination and can therefore be engineered into different reaction regimes, such as ionic bonding, covalent bonding, and defect creation. Micro-Raman mapping showed that the plasma-based chlorination process is a uniform process on the micrometer scale.