Methods are disclosed for activating dopants in a doped semiconductor substrate. A carbon precursor is flowed into a substrate processing chamber within which the doped semiconductor substrate is disposed. A plasma is formed from the carbon precursor in the substrate processing chamber. A carbon film is deposited over the substrate with the plasma. A temperature of the substrate is maintained while depositing the carbon film less than 500° C. The deposited carbon film is exposed to electromagnetic radiation for a period less than 10 ms, and has an extinction coefficient greater than 0.3 at a wavelength comprised by the electromagnetic radiation.