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RESEARCH PRODUCT

Some fundamentals of the vapor and solution growth of ZnSe and ZnO

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Abstract Some fundamentals of ZnSe and ZnO vapor and solution growth are investigated. Residual water present in gases or gaseous mixtures such as H 2 , Ar or H 2 +H 2 O is shown to act as a sublimation activator in the vapor-phase transport of both compounds. The processes involved in the growth by chemically activated sublimation with such gases and gas mixtures have been studied by close-spaced vapor transport (CSVT). The ZnSe growth rate is found to be constant, while in the ZnO case a high initial growth rate is followed by slower growth subsequently. Using a theoretical model, the thermodynamic constants of the transport – energies of activation, sublimation and condensation and enthalpy of formation – are determined independently from a fit to the variation of the growth rate as a function of the substrate temperature. No classical chemical transport reactions are shown to correspond to the sublimation mechanism, that is supposed to be chemically assisted by residual water. In the case of ZnO, the sublimation mechanism is found to be more complex than for ZnSe, as expressed by the variation of the growth rate with time. As an alternative to this chemically assisted sublimation, chemical vapor transport using chlorine as chemical agent is proposed for ZnO. Significant transport is found to occur at temperatures of about 1000°C. Concerning solution-growth, the pseudo-binary PbCl 2 –ZnO phase diagram established by differential thermal analysis (DTA) shows PbCl 2 to be a good solvent of ZnO, as for ZnSe. Zn–In alloys are proposed as good alternative solvents for ZnO not having the great reactivity of the PbCl 2 –ZnO mixture with silica.