Novel Concepts for Low-pressure, Low-temperature Nanodiamond Growth Using MW-linear Antenna Plasma Sources
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1203-J05-05
Novel concepts for Low-pressure, Low-temperature Nanodiamond Growth using MW Linear Antenna Plasma Sources Jan Vlček1&2, František Fendrych1, Andrew Taylor1, Irena Kratochvílová1, Ladislav Fekete1, Miloš Nesládek3 and Michael Liehr4 1
Institute of Physics, Academy of Sciences of the Czech Republic, v.v.i, Prague 8, Czech Republic Institute of Chemical Technology, Department of Physics and Measurements, Prague 6, Czech Republic. 3 IMOMEC division, IMEC, Institute for Materials Research, University Hasselt, Wetenschapspark 1, B3590 Diepenbeek, Belgium 4 Leybold Optics Dresden GmbH, Dresden, Germany 2
ABSTRACT Industrial applications of PE MWCVD diamond grown on large area substrates, 3D shapes, at low substrate temperatures and on standard engineering substrate materials require novel plasma concepts. Based on the pioneering work of the group at AIST in Japan, highdensity coaxial delivery type of plasmas have been explored [1]. However, an important challenge is to obtain commercially interesting growth rates at very low substrate temperatures. In the presented work we introduce the concept of novel linear antenna sources, designed at Leybold Optics Dresden, using high-frequency pulsed MW discharge. We present data on high plasma densities in this type of discharge (> 10 E11 cm-3), accompanied by data from OES for CH4 – CO2 - H2 gas chemistry and the basic properties of the nano-crystalline diamond (NCD) films grown. INTRODUCTION Typical conditions for PE MWCVD (plasma enhanced microwave chemical vapour deposition) growth of diamond films are a mixture of a hydrocarbon and hydrogen with a very low proportion of hydrocarbon and a substrate temperature of about 600-1000ºC [2, 3 & 4]. From the point of view of the material structure and properties, it is important to develop technologies that lead from ultra nanocrystalline diamond – UNCD - (i.e continuously renucleating) to nanocrystalline diamond - NCD - (columnar) type of diamond growth [5]. High substrate temperatures restrict the range of suitable substrates and therefore possible applications of these films. Another restriction of PE MWCVD growth is the growth area; typically it is restricted to a maximum diameter of 15cm. Again this not only restricts the range of applications but also their scale. Limitations of HF CVD (hot filament chemical vapour deposition) processes to produce UNCD and NCD films are described in [6]. They relate to the well known difference between thermal HF CVD and PE MWCVD methods. In the first case the reactive species are produced by thermal decomposition of gases at high gas temperatures, PE MWCVD can work far from thermal equilibrium due to reactions induced by energetic particles (ions, electrons and radicals with energies significantly higher than the gas temperature) and therefore creating fluxes of growth species without heating of the gas. This has a fundamental impact on the possibility of low temperature growth. Further more, in resonance cavity PE MWCVD systems used for
diamond deposition [7 & 8], due to their
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