Al-enhanced low temperature deposition of diamond thin films on hetero-substrates

Synthesis of diamond thin films on aluminum and aluminum-modified Si and steel substrates has been performed at 450 °C with 1%CH4–99%H2 gas mixture in a microwave plasma enhanced chemical vapor deposition (CVD) reactor. A diamond scratching pre-treatment of bulk Al substrate or Al-interlayered Si/steel substrates greatly enhances diamond nucleation, and the diamond films directly synthesized on Al substrate are well faceted, continuous and densely packed. The diamond films synthesized on conventional Fe–Cr and Fe–Cr–Ni type steels are generally of poor quality due to preferential formation of graphitic carbons catalyzed by the base metal iron. An Al thin film interlayer applied on those steel surfaces has markedly enhanced the nucleation and adhesion properties of diamond films, and a direct alloying addition of Al to these steel substrates also promotes the formation of continuous, dense and adherent diamond films.