Production of transition metal-doped ZnO nanoparticles by using RF plasma field

Transition metals, such as tungsten (W), molybdenum (Mo) and chromium (Cr), were doped into ZnO nanoparticles using an RF plasma system. The resulting ZnO nanoparticles with the size of 30-50 nm changed from white to yellowish or to orange depending on the doped transition metals. The doping position of these transition metals in the ZnO crystal was the same as that determined in a previous paper (J. Crystal Growth 265 (2004) 149). It was found that light with wavelength shorter than 385 nm can be removed by doping. The morphological change due to doping of elements was discussed in terms of the difference of ionicity.