Preparation And Study Of Magnetron-sputtered Nickel Oxide And Doped Nickel Oxide Thin Films

Nickel oxide(NiO)semiconductor material has excellent electrical properties and high chemical stability,and thus has potential application in many fields.As a transporting material,NiO films with high mobility and electrical conductivity is still to be studied in preparation and properties especially electrical properties.Magnetron sputtering method has been preferred to prepare NiO films due to its advantages.Thus in this paper,a series of NiO and Zn-or In-doped NiO films were prepared by DC magnetron sputtering.And the effects of oxygen-to-argon ratio,sputtering power,substrate temperature and working pressure were intensively studied on the film's microstructure and optical and electrical properties.As a result,the optimal parameter for excellent transporting materials was obtained as well.In addition,the mechanism for the transition from p type to n type was also proposed.The main results are listed as follows:(1)The NiO film at oxygen-to-oxygen of 1:1 is more valuable in application.The injecting excess of oxygen can introduce more point defects,thus resulting in poor crystallization of the film.(2)As substrate temperature increases,the crystallization of the NiO films is basically improved.At substrate temperature of 600?,the optical absorption edge of the NiO film reaches the maxima value of 3.69 e V,and the hole mobility reaches3.461 cm~2/Vs.NiO film may has an intermediate state between room temperature and substrate temperature of 200?.Confirmed by the Hall data,the NiO film with the intermediate state has the potential to be a p-type hole-transporting material.(3)The working pressure has minor effect on the microstructure of the NiO films,whereas has certain effect on the optical and electrical properties of the films.For the preparation of NiO films,the working pressure has a limit of 1.0 Pa.Below this value,a blue glow phenomenon will occur,which may be due to the ionization of oxygen.The NiO film prepared under the blue glow has a large number of defects.(4)The combination of the doping of zinc or indium and thermal effect results in the transition of conductivity of NiO:Zn and NiO:In films from p-type to n-type.The critical transition temperatures are 400 and 300?,respectively.NiO:In has lower critical transition temperature than NiO:Zn,which is due to the ability to provide extra electrons to the lattice.(5)The n-type NiO:In film at sputtering power of 120 W is best crystallized with an average grain size up to 42.1 nm.The film's mobility almost linearly increases with increase of sputtering power and reaches the maximum value of 0.7134 cm~2/Vs at sputtering power of 140 W,which is greater than that of 0.6078 cm~2/Vs of NiO:Zn films.The film's electrical resistivity generally decreases with increases of sputtering power,indicating that the NiO:In films prepared at high sputtering power have better electrical properties and high potential to be used as the electron-transporting layer.