abstract
The influence of the substrate temperature on the formation of ultrananocrystalline diamond (UNCD) thin films, prepared by an argon-based hot filament chemical vapor deposition (HFCVD), is discussed in this work. The gas mixture used for diamond growth was 1 vol.% methane, 9 vol.% hydrogen and 90 vol.% argon at a total flow rate of 200 sccm and at a total pressure of 30 Torr. The substrate temperature range was from 550 to 850 degrees C at deposition time of 8 h. Mass growth rate was determined at different deposition temperatures. The activation energy for UNCD growth, determined from the Arrhenius plot, was lower (5.7 kcal/mol) than the values found for standard diamond deposition (around 11 kcal/mol). In this work, we suggest that the activation energy was lower because the growth of these films occurs at conditions that there is a high growth competition between diamond phase and sp(2) phases. To support this hypothesis, systematic characterization studies based on Raman scattering spectroscopy, high-resolution X-ray diffractometry and high-resolution scanning electron microscopy were performed. (C) 2009 Elsevier B.V. All rights reserved
keywords
CHEMICAL-VAPOR-DEPOSITION; HOT-FILAMENT REACTOR; NANOCRYSTALLINE DIAMOND; MICROWAVE PLASMA; GROWTH-RATE; ACTIVATION-ENERGY; CVD; RAMAN; CONDUCTIVITY; DEPENDENCE
subject category
Materials Science
authors
Barbosa, DC; Almeida, FA; Silva, RF; Ferreira, NG; Trava-Airoldi, VJ; Corat, EJ
our authors
Flávia Aparecida de Almeida
Post-doc Fellowship
Rui Ramos Ferreira e Silva
Associate Professoracknowledgements
We are grateful to CAPES (Coorclenacao de Aperfei oamento de Pessoal cle Nivel Superior) and FAPESP (Fundaqo de Amparo a Pesquisa do Estado de Seo Paulo) (proc. #07/00013-4) for the financial support of this work, A. J. S. Fernandes for the UV Raman measurements, R. Rapuano for the use of the microbalance, B. D. Moreno and E. C. Almeida for XRD. F. A. Almeida acknowledges FCT for the postdoctoral grant (SFRH/BPD/34869/2007).