Modification on the Microstructure of Ultrananocrystalline Diamond Films for Enhancing Their Electron Field Emission Properties via a Two-Step Microwave Plasma Enhanced Chemical Vapor Deposition Proce

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• 作者：Hsiu-Fung Cheng ; Chuang-Chi Horng ; Horng-Yi Chiang ; Huang-Chin Chen ; I-Nan Lin
• 刊名：Journal of Physical Chemistry C
• 出版年：2011
• 出版时间：July 21, 2011
• 年：2011
• 卷：115
• 期：28
• 页码：13894-13900
• 全文大小：1283K
• 年卷期：v.115,no.28(July 21, 2011)
• ISSN：1932-7455

文摘

The electron field emission (EFE) properties of microcrystalline diamond (MCD) films were markedly improved by using ultrananocrystalline diamond (UNCD) films as the nucleation layer. Thus formed MCD/UNCD composite films possess a low turn-on field ((E₀)_MCD/UNCD = 10.3 V/渭m), which is even smaller than that for the underlying UNCD films ((E₀)_UNCD = 14.7 V/渭m). However, the extent of the enhancement on EFE behavior of the MCD/UNCD films is strongly influenced by the characteristics of the UNCD nucleation layer. The improvement on EFE behavior of MCD/UNCD films is large when the UNCD nucleation layer was grown in H₂-free Ar plasma (CH₄/Ar/H₂ (0%) = 2/98/0) and is small when the UNCD layer was grown in H₂-containing Ar plasma (CH₄/Ar/H₂ (3%) = 2/95/3). Transmission electron microscopy (TEM) examinations reveal that, while both films contain large-grain and ultrasmall grain duplex microstructure, only the former contain nanographites, locating along the interface of large-grain and ultrasmall grain regions. Presumably, the nanographites form an interconnected path that improved the transport of electrons and markedly enhanced the EFE properties of the MCD/UNCD composite films.