Oxygen-defect vacancies that routinely exist in wet production of VO_2 material or on the surface of VO_2 single crystal after surface treatment have significant influence on the metal-insulator phase transition features mainly due to their enhanced effect of doping on V 3d electronic structure. The removal of the surface oxygen defects is highly desired for investigating the VO_2 intrinsic electronic properties. In this work, we propose a charge transfer doping method by using strong electric affinity mole...