abstract
In this work, we investigate the impact of minute amounts of pure nitrogen addition into conventional methane/hydrogen mixtures on the growth characteristics of nanocrystalline diamond (NCD) films by microwave plasma assisted chemical vapour deposition (MPCVD), under high power conditions. The NCD films were produced from a gas mixture of 4% CH4/H-2 with two different concentrations of N-2 additive and microwave power ranging from 3.0 kW to 4.0 kW, while keeping all the other operating parameters constant. The morphology, grain size, microstructure and texture of the resulting NCD films were characterized by using scanning electron microscope (SEM), micro-Raman spectroscopy and X-ray diffraction (XRD) techniques. N-2 addition was found to be the main parameter responsible for the formation and for the key change in the growth characteristics of NCD films under the employed conditions. Growth rates ranging from 5.4 mu m/h up to 9.6 mu m/h were achieved for the NCD films, much higher than those usually reported in the literature. The enhancing factor of nitrogen addition on NCD growth rate was obtained by comparing with the growth rate of large-grained microcrystalline diamond films grown without nitrogen and discussed by comparing with that of single crystal diamond through theoretical work in the literature. This achievement on NCD growth rate makes the technology interesting for industrial applications where fast coating of large substrates is highly desirable. (C) 2015 Elsevier Ltd. All rights reserved.
keywords
CHEMICAL-VAPOR-DEPOSITION; CVD DIAMOND; NITROGEN; MORPHOLOGY; POLYCRYSTALLINE; TEXTURE; MICROSTRUCTURE; FABRICATION; COATINGS; REACTOR
subject category
Materials Science; Physics
authors
Tang, CJ; Fernandes, AJS; Granada, M; Leitao, JP; Pereira, S; Jiang, XF; Pinto, JL; Ye, H
our authors
Sérgio Manuel de Sousa Pereira
Principal Researcheracknowledgements
This work is supported by projects PEst-C/CTM/LA0025/2011 and PTDC/FIS/117632/2010 funded by COMPETE programme - Operational Factors for Competitiveness and FEDER and by national funds through FCT - Portuguese Science and Technology Foundation. The financial support by the National Science Foundation (NSF) of China under grant No. 51102027 is also acknowledged. In addition, we acknowledge the partial financial support by the European Union under Grant Agreement 295208 (CarbonNASA).