Zone model for zinc oxide deposited by combustion chemical vapor deposition

A zone model describing the microstructures of zinc oxide films deposited b y combustion chemical vapor deposition as a function of temperature and pre cursor concentration was developed experimentally. Homologous temperatures from 0.2 to 0.5, and precursor concentrations from 0.0025 to 0.04 M were in vestigated. Zinc 2-ethylhexanoate was used as precursor. Low deposition tem peratures and/or high precursor concentrations favor the growth of amorphou s ZnO (zone A). At moderate deposition temperatures and/or lower precursor concentrations, relatively smooth crystalline, small grained films form (zo ne T microstructure). The largest deposition temperatures and/or lowest pre cursor concentrations result in films with columnar grains (zone II microst ructure). ZnO could not be deposited at homologous temperatures greater tha n approximately 0.5 because of its high vapor pressure. Kinetic measurement s of the zone A to zone T transition resulted in an activation energy of 64 +/- 9 W/mol for the responsible mechanism. Similarly, measurements of grai n size as a function of deposition temperature yielded an activation energy of 60 +/- 21 kJ/mol. These activation energies are consistent with surface diffusion being responsible for both the amorphous to crystalline transiti on and grain growth in the crystalline films. (C) 2001 Elsevier Science B.V . All rights reserved.