Diamond CVD by a Combined Plasma Pretreatment and Seeding Procedure** By Shlomo Zalka Rotter * and Joana Catarina Madaleno A novel nucleation process (NNP), called the Rotter nucleation process in a recent review article, is described in detail in this paper. The NNP is based on the initial formation of a carbon film that, together with the diamond seeds on the surface (by standard seeding), plays an important role in the growth of the diamond layer. In the early stage, NNP induces a lateral growth mode that prevails until the initial grains coalesce and columnar growth begins. This method opens up new ways of using thin diamond films as encapsulation layers, and enables the formation of composite materials based on diamond. Keywords: Diamond film, Nanocrystals, Nucleation, Seeding procedure 1. Introduction The unique properties of diamond (such as high hardness, chemical inertness, thermal conductivity, large band-gap (5.4 eV), and high electron and hole mobilities [1] ) make it the choice material for several applications. Since the initial report by Derjaguin et al. in 1968, [2] CVD- produced diamond has found its way into tribology applications, improving the wear resistance of cutting tools and moulds. [3–5] Its superior properties as a wide band-gap semiconductor have also pushed forward the research into the use of diamond for high-power electronics, [6–9] even though single and polycrystalline diamond films have not won a definitive position as a wide band-gap semiconductor material so far. Nanocrystalline diamond (NCD) films also have an increasing number of applications that were considered to be inconceivable just a few years ago. [10–12] Bulk diamond can be grown by high temperature, high pressure (HTHP) techniques, but the size of the available substrates is very limited, and for sizes above 1 cm 2 the manufacturing process becomes uneconomical or non- viable. On the other hand, plasma enhanced (PE)CVD [13] allows the deposition of diamond on large area foreign substrates, but a nucleation procedure becomes an essential step in order to provide the substrate with an appropriate seeding film for further diamond growth. Many different nucleation methods have been used since the emerging techniques for growing diamond films. The simplest nucleation scheme is a diamond grit-abrading process [14] that can be used only with flat surfaces, and if the substrate is coated with a soft intermediate layer it may be damaged by the harsh abrading action. The ultrasonic treatment [15] can be used with 3D-shaped substrates, and the appropriate choice of the diamond grit and seeding time allows a further control of the nucleation procedure. The use of nanodiamond powders, which can be processed to prevent agglomeration and dispersed in a colloidal solution with appropriate solvents, has enabled nucleation densities higher than 10 12 cm 2 . [16–18] The third widely known procedure is the bias-enhanced nucleation (BEN) method [19] which employs an in-situ surface bombardment by carbon species under an applied negative bias on the substrate. During the bombardment, fragments of the methane, or other carbon source, alter the surface and create surface structures that act as the seeds for the subsequent diamond growth. This method has also been used to fabricate diamond-based device structures, [20,21] and to deposit highly oriented diamond films using Ir/SrTiO 3 substrates, with promising results, [22] but this method may damage the substrate. Maillard-Schaller et al. [23] reported surface damage on a silicon substrate in the form of holes that could be as deep as 2–3 mm and as large as 200–300 nm in diameter. After the nucleation step, the growth is followed by diamond deposition in a standard CVD reactor, under proper growth conditions (GC). The small seeds enlarge in a 3D fashion until they coalesce and touch each other, forming grain boundaries. At this stage the individual crystallites start growing perpendicular to the surface and keep doing so, following the Van der Drift model, [24] until the growth is terminated. The incubation time for the onset of the formation of diamond crystallites can be 15–45 min, depending on the growth parameters. [25] The nucleation process initially proposed by S. Z. Rotter [26,27] in 1996 has been used to successfully deposit diamond on a variety of substrates; [26–31] however, the DOI: 10.1002/cvde.200806745 Full Paper [*] Dr. S. Z. Rotter, Dr. J. C. Madaleno TEMA – Centre for Mechanical Technology and Automation, University of Aveiro Campus de Santiago, Aveiro, 3810-193 (Portugal) E-mail: shlomozalka@ua.pt [**] SZR would like to thank J. E. Butler of NRL and S. L. Heidger of AFRL for their help during his sabbaticals in their respective labs. Chem. Vap. Deposition 2009, 15, 209–216 ß 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim 209