Field Enhancement Mechanisms and Electron Field Emission Properties of Ion Beam Synthesized and Modified SiC/Si Heterost
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FIELD ENHANCEMENT MECHANISMS AND ELECTRON FIELD EMISSION PROPERTIES OF ION BEAM SYNTHESIZED AND MODIFIED SiC/Si HETEROSTRUCTURES W.M. Tsang*, S.P. Wong*, J.K.N. Lindner** *Dept. of Electronic Engineering and Materials Science and Technology Research Centre, The Chinese University of Hong Kong, Hong Kong, China **Universität Augsburg, Institut für Physik, D-86135 Augsburg, Germany
ABSTRACT SiC/Si heterostructures were synthesized by high dose carbon implantation into silicon using a metal vapor vacuum arc ion source. Their electron field emission properties were studied and correlated with results from other characterization techniques including atomic force microscopy (AFM), conducting AFM, Fourier transform infrared absorption spectroscopy, x-ray diffraction and photoelectron spectroscopy. It is clearly demonstrated that there are two types of field enhancement mechanisms responsible for the improvement of the electron field emission properties of these ion beam synthesized SiC/Si heterostructures, namely, the surface morphology effect and the local electrical inhomogeneity effect. The dependence of the FE properties on the carbon implant dose and thermal annealing conditions could be understood in terms of these two field enhancement mechanisms. It is also demonstrated that improvement in the FE properties can be achieved by implanting tungsten ions into these SiC/Si heterostructures. INTRODUCTION In recent years, there has been much interest in the study of field emission (FE) properties of carbon containing materials such as diamond and diamond films [1, 2], amorphous carbon [3-8], nanotubes [9, 10], and silicon carbide layers [11, 12]. Some of these material systems showed a very low turn-on field for electron emission typically smaller than 10V/µm [1, 3-11]. However, the mechanisms responsible for these good FE properties are not completely understood. For example, the good FE properties with a very low turn-on field of about 1V/µm from ion beam synthesized SiC/Si heterostructures were attributed to local field enhancement due to a surface morphology effect [11]. It was proposed that the origin of field enhancement in FE from amorphous carbon films was associated with the dielectric inhomogeneity within the films [5-8]. In this work, we shall demonstrate that both the surface morphology and the electrical inhomogeneity in the layer could lead to local electric field enhancement and hence to the improvement of the FE properties in the ion beam synthesized (IBS) SiC layers. We shall also show that improvement of the FE properties of the IBS SiC layers can be achieved by tungsten implantation. EXPERIMENTAL Ion beam synthesis (IBS) of SiC/Si heterostructures was performed by high dose carbon implantation into n-type (100) silicon wafers with a resistivity of 0.01-0.02 Ω-cm to doses ranging from 0.75 to 1.2×1018 cm-2 using a metal vapor vacuum arc (MEVVA) ion source at an *
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extraction voltage of 35 kV. The formation of an amorphous SiC layer in the as-implanted samp
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