Diamond exhibits unique physical properties, such as extreme mechanical hardness, highest known thermal conductivity, broad optical transparency, chemical inertness and biocompatibility. The interest towards diamond has led to spectacular advancements in the development of techniques, e.g., microwave plasma enhanced chemical vapor deposition (MWPECVD), for growing thin films on various substrates. Specifically in the last years, nanocrystalline diamond (NCD) films have attracted great interest as smooth materials and are exploited in several applications, such as coatings, seals, biomedical devices, biosensors, field-emission cathodes and displays, MEMS/NEMS devices and switches for wireless communications. Since the pioneering work of Gruen [D.M.Gruen, Annu.Rev.Mater.Sci. 29 (1999) 211], argon-rich CH4-Ar-H2 gas mixtures represent an innovative and simple way to produce NCD films by MWPECVD. However, to get stable plasmas at low H2 mixture percentage, the standard Astex-type reactors must be modified, as suggested by the same Gruen and other research groups [K.Teii and T.Ikeda, Appl.Phys.Lett. 90 (2007) 111504]. In the present work, we have developed a new procedure to deposit NCD films on pre-treated silicon substrates without modifying the Astex-type reactor and using CH4-Ar-H2 (1-89-10%) gas mixture. In our reactor the 10% of H2 in the mixture assures plasma stability conditions. The key step of the process is the growth of an initial buffer layer, on which the NCD deposition takes place. The buffer layer is easily obtained under typical microcrystalline diamond growth conditions (CH4-H2 mixtures). The effect of the substrate temperature was investigated on the film deposition rate and on the morphology, surface roughness and bonding characteristics of films grown with and without buffer layer. The advantages of the buffer layer are soon visible to the naked eye for the extraordinary uniformity, continuity and smoothness of the NCD films. On the contrary, the films grown without buffer layer are inhomogeneous, non-continuous and rough with surface and interfacial pinholes and big spherical agglomerates.
Nanocrystalline diamond films produced by microwave plasma enhanced chemical vapor deposition
G Cicala;
2012
Abstract
Diamond exhibits unique physical properties, such as extreme mechanical hardness, highest known thermal conductivity, broad optical transparency, chemical inertness and biocompatibility. The interest towards diamond has led to spectacular advancements in the development of techniques, e.g., microwave plasma enhanced chemical vapor deposition (MWPECVD), for growing thin films on various substrates. Specifically in the last years, nanocrystalline diamond (NCD) films have attracted great interest as smooth materials and are exploited in several applications, such as coatings, seals, biomedical devices, biosensors, field-emission cathodes and displays, MEMS/NEMS devices and switches for wireless communications. Since the pioneering work of Gruen [D.M.Gruen, Annu.Rev.Mater.Sci. 29 (1999) 211], argon-rich CH4-Ar-H2 gas mixtures represent an innovative and simple way to produce NCD films by MWPECVD. However, to get stable plasmas at low H2 mixture percentage, the standard Astex-type reactors must be modified, as suggested by the same Gruen and other research groups [K.Teii and T.Ikeda, Appl.Phys.Lett. 90 (2007) 111504]. In the present work, we have developed a new procedure to deposit NCD films on pre-treated silicon substrates without modifying the Astex-type reactor and using CH4-Ar-H2 (1-89-10%) gas mixture. In our reactor the 10% of H2 in the mixture assures plasma stability conditions. The key step of the process is the growth of an initial buffer layer, on which the NCD deposition takes place. The buffer layer is easily obtained under typical microcrystalline diamond growth conditions (CH4-H2 mixtures). The effect of the substrate temperature was investigated on the film deposition rate and on the morphology, surface roughness and bonding characteristics of films grown with and without buffer layer. The advantages of the buffer layer are soon visible to the naked eye for the extraordinary uniformity, continuity and smoothness of the NCD films. On the contrary, the films grown without buffer layer are inhomogeneous, non-continuous and rough with surface and interfacial pinholes and big spherical agglomerates.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
