▎ 摘　　要

Graphene based pn-junctions attained significant interest owing to its technological applicability. A variety of methods are being employed to form a pn-junction in graphene. Majority of methods induce impurities which influence the structural and electrical properties of graphene. Here we study the ionic physisorption effect on the graphene surface due to KNO3 treatment and formation of a pn-junction in graphene/hBN heterostructure by chemical treatment. Raman spectroscopic analysis confirms the high quality of graphene. Electrical transport measurements of pristine and KNO3 doped graphene are also carried out, which reveals the formation of pn-junction in graphene/hBN heterostructure. Furthermore, the quality of pn-junction is improved by treating the junction region with deep ultraviolet light (DUV) irradiations. These results demonstrate that chemical doping together with the DUV light on graphene/hBN heterostructure provides a new direction to form pn-junction that can be utilized for technological applications.