Investigation of atmospheric pressure nitrogen plasma assistance on mist CVD of zinc oxide thin films

Zinc oxide (ZnO) is a widely applied material, but there are problems with equipment costs and film formation rates. In this study, we performed plasma assistance for mist CVD, which is known as an inexpensive and safe film formation method, and formed ZnO.

An atmospheric pressure nitrogen plasma jet (N₂ APPJ) was generated by supplying the high voltage (9 kV) to electrodes of plasma source at the nitrogen gas flow rate of 5 l/min. An aqueous solution (0.02 mol/l) made by dissolving zinc acetate dihydrate in pure water was made into a mist by an ultrasonicator and fed into the chamber as the ZnO source. The ZnO thin film was formed for 30 minutes on the silicon substrate placed on a stage heated to 400?. The distance between the substrate and the APPJ source was set to 10 mm.

ZnO formed by the mist CVD with the APPJ assistance has a structure composed of larger particles compared with that without the APPJ assistance. Moreover, the deposition rate increased up to 5 times. This result indicates the decomposition of raw materials was additionally promoted by the reactive species emitted from the N₂ APPJ in addition to the pyrolysis.