Spray plasma device, a new method to process nanostructured layers. application to deposit ZnO thin layers.
The aim of this paper is to present a new plasma spray device to deposit nanostructured films. In this process, aqueous droplets of a starting material, in this case, a nitrate salt, of small and uniform size produced in an aerosol generator are injected into a low pressure plasma reactor. Droplets are then submitted to the reactivity of plasma and projected against a substrate where they form the final film. The reactor is designed to reduce the turbulence that results in coalescence of the particles and affects the uniformity of the deposited films. The plasma is produced by an inductive RF generator that avoids the contamination of the layers by electrodes. The control of plasma gas composition, i.e., argon and oxygen, permits adjustment of the concentration of reactive species leading to control the stoichiometry of the deposited layers. The ability of this process to produce nano scale zinc oxide films by the use of an aqueous solution containing Zn(NO3)2 is demonstrated. The films obtained under defined experimental conditions are smooth, colorless and transparent. SEM and AFM photographs show the formation of uniform layers with 20 to 60 nm in thickness. XRD patterns of deposited films showed that preferential c-axis orientation of crystallites depends highly on the concentration of Zn(NO3)2 in the starting solution. Willamson-Hall method in accordance with AFM photographs showed that the size of crystallites ranges between 24 and 34 nm.
Nikravech
Mehrdad
M
LIMHP Université Paris 13, Institut Galilée. Av. J.B. Clément, 93430 Villetaneuse, France.