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 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.Thick (around 3 ?m) and thin (48-310 nm) NCD films have been produced from Ar-rich CH4/Ar/H2 (1/89/10 %) and H2-rich CH4/H2 (1/99 %) microwave plasmas, respectively. During the deposition the working pressure and microwave power were 140 mbar and 950 Watt for CH4/Ar/H2 plasmas, and 50 mbar and 1000 Watt for CH4/H2 plasmas. In the experiments the total flow rate (?tot, 100sccm) was held constant. The deposition rate and the nucleation enhancement have been monitored in-situ and in real-time by pyrometric and laser reflectance interferometry for micrometer and nanometer thick films.The thick NCD films were obtained with and without an initial buffer layer (BL). The BL is easily obtained under typical microcrystalline diamond growth conditions (CH4/H2 mixtures). The effect of the deposition temperature (TD, 630-900°C) was investigated on the deposition rate, the morphology, the surface roughness and the bonding characteristics of the films grown with and without BL. The advantages of the BL are visible to the naked eye for the extraordinary uniformity, continuity and smoothness (roughness around 50 nm) of the NCD films. On the contrary, the films grown without BL appear inhomogeneous, non-continuous and rough (100-190 nm) with surface and interfacial pinholes and big spherical agglomerates.The thin NCD films were grown on Si substrates treated by two different methods, i.e. ultrasonic agitation in a suspension of diamond powders of 40-60 ?m or combitanorial approach in a suspension of mixed diamond powders of 250nm and 40-60 ?m. The process time of deposition was varied from 7 to 66 min by keeping constant the deposition temperature around 815 °C. The nanometer thick films with roughness of about 20 nm were easily obtained when the Si surface is treated by the combinatorial approach.The present experimental results show that the buffer layer procedure allows a good preservation of the surface of treated Si substrate and the combinatorial approach promotes effectively the seeding of the Si surface.

Autore Pugliese

• Cicala Grazia

Tutti gli autori

• G. Cicala; V. Magaletti

Titolo volume/Rivista

Non Disponibile

Anno di pubblicazione

2013

ISSN

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ISBN

978-88-8305-101-2

Numero di citazioni Wos

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Settori ERC

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