Influence of crystal structure of high purity iron substrate on diamond growth by chemical vapor deposition

Abstract

Diamond growth by chemical vapor deposition technique using the iron substrates that have a high purity but different crystallite size were studied. The carbon diffusion into their substrates under the diamond growth has been measured.The crystallite sizes of the iron materials were characterized by X-ray diffraction analysis. In addition, cross-sectional areas of the iron substrate before the diamond growth were observed by scanning electron microscope. The crystal structures and crystalite sizes of iron substrates influenced the crystalline quality of the growth diamonds. Moreover, the carbon diffusion density into the iron substrates in initial stage of diamond growth was estimated by an electron probe microanalyzer (EPMA). In the EPMA analysis, the area of 600μm in the depth and the width of 400μm were observed. In the case of the substrate with large crystallite size, the depth of high carbon concentration area (more than 1 %) was 70μm. On the other hands, the depth was 130μm in the case of the substrate with small crystallite size. It was found that the carbon diffusion density strongly depended upon the crystallite size of the base iron substrates before the growth.