Analytical TEM study of CVD diamond growth on TiO₂ sol-gel layers

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• 作者：Ying-Gang Lu^a ; ^{yinggang.lu@ua.ac.be} ; Johan Verbeeck^a ; Stuart Turner^a ; An Hardy^b ; ^c ; Stoffel D. Janssens^b ; ^c ; Christopher De Dobbelaere^b ; Patrick Wagner^b ; ^c ; Marlies K. Van Bael^b ; ^c ; Ken Haenen^b ; ^c ; Gustaaf Van Tendeloo^a
• 关键词：Diamond film ; Plasma CVD ; Diffusion ; High resolution electron microscopy
• 刊名：Diamond and Related Materials
• 出版年：2012
• 期刊代码：30_09259635
• 类别：ms
• 出版时间：March, 2012
• 卷：23
• 期：Complete
• 页码：93-99
• 文件大小：2863 K

摘要

The early growth stages of chemical vapor deposition (CVD) diamond on a sol-gel TiO₂ film with buried ultra dispersed diamond seeds (UDD) have been studied. In order to investigate the diamond growth mechanism and understand the role of the TiO₂ layer in the growth process, high resolution transmission electron microscopy (HRTEM), energy-filtered TEM and electron energy loss spectroscopy (EELS) techniques were applied to cross sectional diamond film samples.

We find evidence for the formation of TiC crystallites inside the TiO₂ layer at different diamond growth stages. However, there is no evidence that diamond nucleation starts from these crystallites. Carbon diffusion into the TiO₂ layer and the chemical bonding state of carbon (sp²/sp³) were both extensively investigated. We provide evidence that carbon diffuses through the TiO₂ layer and that the diamond seeds partially convert to amorphous carbon during growth. This carbon diffusion and diamond to amorphous carbon conversion make the seed areas below the TiO₂ layer grow and bend the TiO₂ layer upwards to form the nucleation center of the diamond film. In some of the protuberances a core of diamond seed remains, covered by amorphous carbon. It is however unlikely that the remaining seeds are still active during the growth process.