Controllable Synthesis Of Nitrogen-doped Graphene And Characterizations Of Its Transport Properties

Nowadays,as a gate node in silicon complementary metal-oxide-semiconductor(CMOS)device gets smaller,the rising leakage current and power dissipation constitute the major challenge for further reducing the size together.Next-generation electronics call for the alternatives of newly-developed channel materials or novel device concept.Fortunately,after the successful cleavage of graphene in 2004,two-dimensional materials as strong competitors began to enter the historical stage for new devices.Graphene is a two-dimensional crystal formed by sp~2 hybridized carbon atoms.It has excellent electrical,optical,mechanical and chemical properties,among which the most remarkable one is its electrical property.High carrier mobility(200000 cm~2/(Vs)),anomalous quantum hall effect,bipolar field effect and superconductivity endow graphene with the great potentials in the field of electronic devices.For pristine graphene without doping,the Fermi level is precisely at the Dirac point.To date,considerable efforts have been focused on preparing n-type or p-type doped graphene to fully realize graphene-based electronics.This dissertation is devoted to the controllable synthesis of nitrogen-doped graphene(NG)and the electrical properties of field effect transistor(FET)devices.The content of this dissertation is shown as follows:(1)Pyridine molecules have been chosen as carbon and nitrogen source for the chemical vapor deposition(CVD)synthesis of the nitrogen-doped graphene.The experimental results show that location of the copper foil,the environment of the pyridine tank,the CVD system and copper foils with different crystal surfaces holds a significant impact on the growth.With the pyridine as the liquid precursor,the flight distance,volatilization rate and deposition location have been considered carefully.Raman characterization and X-ray photoelectron spectroscopy(XPS)characterization confirmed the existence of pyridinic nitrogen and pyrrolic nitrogen in NG,which mainly exists in the edge of NG.Scanning transmission electron microscopy(STEM)characterization shows that there are no defects in NG,and the nitrogen atoms in NG are suspected to distribute randomly in the graphene lattice.(2)The electrical test of NG-FET devices shows that the adsorption of water and oxygen impurities when exposed in the air need be removed carefully before detecting the pristine electrical properties.After a series of treatments,the ambipolar behavior has been observed clearly.The experiment of changed temperature of device shows the current decreased and the Dirac point moved to the left when the temperature goes down;The experiment of laser irradiation on the device shows that the sample will show bipolarity effect after laser irradiation,it indicates the environment has influence on the electrical properties of NG.