Zinc Oxide/Copper Oxide Mixed Films Deposited by CVD
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Zinc Oxide/Copper Oxide Mixed Films Deposited by CVD Yuneng Chang, Chihhsiang Yeh Lunghwa Institute of Technology, Deptartment of Chemical Engineering, Gueishan, Taoyuan, Taiwan R.O.C. ABSTRACT Metal organic chemical vapor deposition (MOCVD) was used to prepare ZnO/Cu2O mixed films. The process condition studied were: deposition temperature from 360oC to 440oC, partial pressures of oxygen, 190-380 torr, precursor copper acetylacetonate (Cu(acac)2), 0.21 torr, and zinc acetylacetonate(Zn(acac)2), 0.45 torr. AES and XPS analysis showed average elemental content being Cu, 52-66%, Zn, 11-20%, O, 30-40%. Copper presented primarily as Cu(I) ions, and Zn as Zn(II) ions. SEM, SAM and XRD indicated that deposited films were polycrystalline with composite structure. Some films had a continuous ZnO thin layer with flat surface, equiax fine grained. On the top of ZnO layer were covered by discrete, irregular shape, coarse Cu2O grains. Primary Cu2O phases were (110), (111), and (200) orientation. ZnO phases were (002), and (103). SEM showed the impact of deposition temperature on Cu2O grain size. Such data were used to estimate the activation energy for grain growth. In fact, to our experiences from these studies, binary metal oxide CVD showed a wide spectrum of film microstructure and morphology. These phenomena reflect the result caused by both thermodynamics as film composition, and kinetics as mass transfer/ surface reaction rate. INTRODUCTION Simultaneously depositing Zinc oxide/copper oxide mixed films is an attractive research topic. Zinc oxide and copper oxide are the basic ingredients for methanol synthesis catalysts. Recent research showed the phase boundary between ZnO domain and Cu2O domain were of great importance to catalyst surface activities[1]. For piezoelectric micro acuator use, Cu doped ZnO films with higher resistivity, which allow lower operation frequency(
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