Oriented Growth of Thin Films of Samarium Oxide by MOCVD
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Oriented Growth of Thin Films of Samarium Oxide by MOCVD K. Shalini and S.A. Shivashankar Materials Research Centre, Indian Institute of Science, Bangalore – 560 012, India. ABSTRACT Thin films of samarium oxide, Sm2O3, have been grown on Si(100) and fused quartz by lowpressure MOCVD using an adducted β-diketonate precursor developed in house. It is found that the nature of the film grown is strongly dependent on substrate temperature. As examined by Xray diffraction, the films of Sm2O3 grown at lower temperatures (~550°C) on fused quartz are cubic and display a random grain orientation, while they become highly oriented in the (111) direction as the growth temperature is increased (to 625°C). On Si(100), highly oriented films of cubic Sm2O3 are obtained at a substrate temperature of 625°C. When the growth temperature is raised, the phase changes to monoclinic. The morphology of the films grown on both quartz and Si(100) substrates has been studied by scanning electron microscopy and atomic force microscopy. The growth of strongly oriented Sm2O3 on the disordered surface of fused quartz may be interpreted as being driven by the minimization of surface energy. INTRODUCTION Metal-oxide-semiconductor (MOS) structures are widely used in modern solid-state electronics. It is expected that, as dimensions of silicon integrated circuits shrink further, silicon dioxide would have to be replaced as the gate dielectric by a material with a higher dielectric constant. This gives rise to the necessity of finding and investigating the properties of new insulating materials. Rare earth oxides are examples of such materials, characterized by high values of dielectric constant (8-20), high resistivity, and high chemical and thermal stability. However, silicon MOS structures with rare earth oxides have not been investigated extensively. Very thin layers of rare earth oxides, such as Sm2O3 and epitaxial Gd2O3, grown by evaporation techniques have been proposed recently as the gate dielectric material for VLSI circuits of the future in both Si and GaAs technologies [1,2]. Chemical vapor deposition (CVD) technique has several advantages over other physical processes, such as the capability for large area deposition, excellent compositional control and film uniformity, high film densities and deposition rates and, more importantly, excellent conformal coverage at device dimensions
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