Kinetic study of MOCVD fabrication of copper(I) and copper(II) oxide films

Growth kinetics of Cu2O and CuO films has been studied using the Cu-II acetylacetonate precursor in a low-pressure (11.3 Torr) MOCVD reactor. Pure Cu2O forms in the 2.7-6 Torr P-O2 and 0-3 mTorr P(Cu(acac)2) ranges at deposition temperature of 300 degrees C. Beyond 3.74 Torr P-O2, Cu2O films show a [111] texturing. Conclusive evidence for the occurrence of a Langmuir-Hinshelwoold mechanism, involving non-competitively adsorbed reagents, has been obtained. Above 8 Torr P-O2 CuO films have been grown under a reaction rate limited regime at temperatures as low as 285 degrees C. The apparent activation energies are 18 +/- 2 kJ/mol and 22 +/- 3 kJ/mol at 0.7 and 2 mTorr P(Cu(acac)2), respectively, The present data are consistent with a kinetic model for CuO formation based on the surface reaction between reversibly adsorbed molecular Cu(acac)(2) and weakly adsorbed O-2. The dependence of kinetic parameters upon the temperature brings about a 40 +/- 6 kJ/mol value of the heat of adsorption of the molecular precursor. Homogeneous and smooth surfaces are associated with CuO (111) oriented films. Homogeneous surfaces with a greater grain size (0.2-0.4 mu m), are observed for CuO. Randomly oriented Cu2O samples are much less homogeneous with grain size ranging from 50 nm to 0.5 mu m.