N doping using N_(2)O and NO sources: From the viewpoint of ZnO

摘要

A study of N doping using N_(2)O and NO sources on ZnO, which may prove important for the N doping of oxide materials, was performed by investigating the doping processes of N atoms by each source together with the various properties for the grown N doped ZnO films. N_(2)O was employed as the radio-frequency (rf) plasma source to produce radical N_(2)~(*) species that could effectively incorporate N atoms above 10~(20) cm~(-3) into ZnO, which was similar to N doping using N_(2) as the source. In contrast, it was found that the ZnO films doped with a N concentration above 10~(20) cm~(-3) were easily obtained using a gas flow of NO. The N concentration could be controlled systematically by the simultaneous gas flow of NO and O_(2) sources. The basis of N doping using a NO source could be related to the free radical characteristic of NO molecular. This idea was proposed from the results that the N concentrations doped to ZnO using a gas flow of N_(2)O and N_(2), which have the characteristics of neutral and nonreactive molecules in air, were in the ranges from 10~(18) to 10~(19) cm~(-3). Further, our investigations clarified that the structural, optical, and electrical properties for the N doped ZnO films were not quite dependent on the N_(2), N_(2)O and NO sources used as N dopants. This work proposes that NO is a promising source as a N dopant that can be employed without using a rf plasma source in the application of physical vapor deposition techniques that are indispensable for producing radical N_(2)~(*) species through a rf plasma source to achieve the efficient incorporation of N atoms when N_(2) and N_(2)O sources are used as N dopants.