▎ 摘　　要

An approach to decrease the P-doping density of graphene and increase the mobility of graphene field-effect transistors (GFETs) is reported. With a layer of natural aluminium oxide (natural-AlOx) thin film covered on the surface of graphene, the Dirac point voltage of the GFETs decreases 25 V while it experiences the mobility increase of 42 cm(2)/(V s) after exposure in the atmosphere for 1 month. To understand this phenomenon, other two situations are researched, the Dirac point voltage of the identical GFETs with no thin film on graphene increases more than 15 V and its mobility decreases 90 cm(2)/(V s) after 1 month. The last situation is that the Dirac point voltage and the mobility have no significant changes with an AlOx deposited by electron beam evaporation (Al2O3-EBE) on graphene. These phenomena indicate that the natural-AlOx thin film is capable of reducing p-type impurities on the graphene and bringing the better reliability to the GFETs.