Deposition of zinc oxide thin films by combustion CVD

Abstract

Combustion chemical vapor deposition (combustion CVD) has been developed to produce zinc oxide thin films. Combustion CVD is different from conventional CVD in that it is performed in a flame. The flame provides the energy, primarily in the form of heat, necessary to deposit ceramic thin films. Zinc 2-ethylhexanoate was dissolved in an organic solvent to produce the flammable solutions used to deposit zinc oxide films onto amorphous silica substrates. Zinc ion concentrations in the solutions were 0.01 M. Substrate temperatures were monitored and controlled during the depositions. Several substrate temperatures, ranging from 190–850°C, were used. Crystalline films up to 1.4 μm-thick were produced at deposition rates up to 5 μm/h. The films were of the hexagonal wurtzite structure and displayed a strong preferred orientation of (002) normal to the substrate surfaces. A variety of microstructures were produced depending on substrate temperature during deposition. Scanning electron microscopy, transmission electron microscopy, X-ray diffraction and Rutherford backscattering spectrometry were used to characterize the films.