Enhanced spin-orbit coupling in dilute fluorinated graphene

The preservation and manipulation of a spin state mainly depends on the strength of the spin-orbit interaction. For pristine graphene, the intrinsic spin-orbit coupling (SOC) is only in the order of few mu eV, which makes it almost impossible to be used as an active element in future electric field controlled spintronics devices. This stimulates the development of a systematic method for extrinsically enhancing the SOC of graphene. In this letter, we study the strength of SOC in weakly fluorinated graphene devices. We observe high non-local signals even without applying any external magnetic field. The magnitude of the signal increases with increasing fluorine adatom coverage. From the length dependence of the non-local transport measurements, we obtain SOC values of similar to 5.1 meV and similar to 9.1 meV for the devices with similar to 0.005% and similar to 0.06% fluorination, respectively. Such a large enhancement, together with the high charge mobility of fluorinated samples (mu similar to 4300 cm(2) V-1 s(-1)-2700 cm(2) V-1 s(-1)), enables the detection of the spin Hall effect even at room temperature.