Etch-delineation of defects in diamond by exposure to an oxidizing flame
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An experimental study of the etching properties of defects in diamond using propane flame exposure in air is presented. Both natural diamond crystals and polycrystalline diamond films were exposed to a flame for an optimum time of 3 - 4 s. This process topographically delineates defects in diamond via an accelerated etch rate at defect sites. Using transmission electron microscopy (TEM) to determine the exact nature and density of defects present in the diamond, we have found a direct correlation between topographical delineation observed by scanning electron microscopy (SEM) and the defect structure observed by TEM.
Diamond has several properties that make it desirable for electronic applications.1 Foremost are diamond's high thermal conductivity (-2000 W n T 1 K" 1 ) and wide band gap (5.48 eV). However, before the impressive attributes of diamond can be fully exploited for electronic device purposes, several manufacturing technologies must be developed. First among these is the growth of electronic-quality diamond thin films of high microstructural perfection. Considerable worldwide effort has gone into developing chemical vapor deposition (CVD) techniques for growing high-quality diamond, 23 and considerable progress has been made. And, by analogy with the historical development of other semiconductor materials, techniques are evolving to determine accurately the crystalline quality of grown diamond. For example, Raman spectroscopy has been used extensively to ascertain the presence of unwanted sp2 bonding in diamond films.4 In other semiconductor material technologies, wet chemical etch delineation is used to ascertain defects at the per cm2 level. But this technique is lacking in diamond technology, as diamond is virtually impervious to standard wet chemical etchants. This communication describes a defect delineation method for diamond, which involves anisotropic defect etching using a propane torch. Previous etching studies on diamond have been undertaken to investigate feasibility of patterning,5 to determine etch removal rates,6"11 to identify the role of non-diamond phase removal during the growth process,5 and to assess crystalline quality through preferential etching of defects,8'12 to name a few. Several methods that have proven successful in etching both diamond and non-diamond phases have employed both (a) an oxygen-containing gas and (b) an activation mechanism. Etching under these conditions is generally believed to occur via the oxidation and volatilization of the carbon J. Mater. Res., Vol. 8, No. 6, Jun 1993 http://journals.cambridge.org
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phase(s). It has been suggested that etching of diamond proceeds through graphitization followed by oxidation of the graphitic phase.8 Several observations regarding etch rates have been made: (1) non-diamond phases etch faster than diamond,5-7'9'11 (2) natural diamond etches faster than plasma-enhanced chemical vapor deposition (PECVD)-grown diamond,6'9'11 and (3) diamond etches faster at grain boundaries and other defects than nondef
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