Selective Seeding and Growth of Nanocrystalline CVD Diamond on Non-Diamond Substrates
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Selective Seeding and Growth of Nanocrystalline CVD Diamond on Non-Diamond Substrates P. Pobedinskas1, S.D. Janssens1, J. Hernando2, P. Wagner1,3, M. Nesládek1,3, K. Haenen1,3 1 Hasselt University, Institute for Materials Research (IMO), Diepenbeek, Belgium 2 Universidad de Castilla La Mancha, Departamento de Ingeniería Eléctrica, Electrónica, Automática y Comunicaciones, E.T.S.I. Industriales, Ciudad Real, Spain 3 IMEC vzw, IMOMEC, Diepenbeek, Belgium ABSTRACT A study is presented on nanocrystalline diamond (NCD) growth on different substrates, including silicon with and without different metallic interlayers, on aluminum nitride (AlN), and on a Si/AlN-based cantilever. It is shown that non-diamond substrate treatment prior to NCD growth is important for achieving high nucleation densities. AFM measurements reveal that an additional Si surface pretreatment with hydrogen plasma increases the nucleation density by a factor of four. A similar effect was indirectly demonstrated with acidic pretreatment of AlN. In both cases it is believed that the surface roughening is the key factor for explaining this phenomenon. INTRODUCTION Chemical vapor deposition (CVD) diamond is a versatile material with extreme mechanical, thermal, electronic and optical properties. Because of its very good chemical stability and bio-inertness, it is currently being studied for a range of applications that make use of its surface and bulk properties, including novel generation of neuroprosthetics [1,2] and (biosensing) diamond-based acoustic devices [3]. The synthesis of ~100 nm thin nanocrystalline diamond (NCD) films by the microwave plasma enhanced CVD (MW PE CVD) technique has proved an enormous step forward for this material to show its potential in action [4,5]. However, the diamond nucleation step is critical for CVD of diamond on non-diamond substrates, i.e., for heteroepitaxial as well as polycrystalline growth. In general, growth on such foreign substrates requires artificial formation of diamond nucleation sites on the substrate’s surface. The use of state-of-the-art seeding procedures based on water-based colloidal solutions of ultra dispersed nanodiamond powder, allow the deposition of closed films of less than 100 nm on 2D as well as 3D structures, minimizing deposition times while retaining an acceptable surface roughness [6]. In this work it will be shown that the ~10 nm in size nanodiamond (ND) particles adhere to the surface by simple van der Waals forces. This adhesion can be simply enhanced by exposing the substrate surface, e.g. of silicon, to a pure hydrogen plasma. Some possible explanations for this observation are suggested although further research needs to be done to clarify this effect. In the second part of this work deposition of NCD on a variety of substrates was investigated, using a conventional methane/hydrogen plasma for diamond growth. Here as well, the possibility of nucleation enhancement will be demonstrated.
EXPERIMENT NCD films were grown in an ASTeX 6500 series MW PE CVD reactor. Amongst the differen
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