Novel high frequency pulsed MW-linear antenna plasma-chemistry: Routes towards large area, low pressure nanodiamond growth ☆ Andrew Taylor a, ⁎, František Fendrych a , Ladislav Fekete a , Jan Vlček b , Vladimíra Řezáčová c , Václav Petrák c , Jaroslav Krucký c , Miloš Nesládek d , Michael Liehr e a Institute of Physics, Academy of Sciences of the Czech Republic, v.v.i, Prague 8, Czech Republic b Department of Physics and Measurements, Institute of Chemical Technology Prague, Technicka 5, CZ-16628, Prague 6, Czech Republic c Czech Technical University in Prague, Faculty of Biomedical Engineering, Sítná sq. 3105, 272 01 Kladno 2, Czech Republic d IMOMEC division, IMEC, Institute for Materials Research, University Hasselt, Wetenschapspark 1, B3590 Diepenbeek, Belgium e Leybold Optics Dresden GmbH, Dresden, Germany abstract article info Available online 12 January 2011 Keywords: Nanodiamond High frequency Microwave plasma enhanced CVD OES Raman Current experimental microwave plasma enhanced chemical vapour deposition (MW PECVD) concepts for diamond thin films do not allow scaling up towards large areas, which is essential for microelectronic industries. Also, current growth temperatures are rather high and not compatible with processing technologies. In the current work we demonstrate a breakthrough concept using a high frequency (HF) pulsed MW-linear antenna plasma configuration, allowing a scalable concept. By using HF pulses non-linear MW absorption conditions are reached, allowing a reduction of input power to 4 W/cm 2 compared with typically 100–200 W/cm 2 for resonance cavity applicators. Despite the factor of 50 power reduction, the growth rate obtained at 450 °C is comparable to or higher than that of resonance cavity systems. Our concept is a significant improvement as compared to [1,3] previous methods of nanodiamond growth. The resulting diamond films show columnar growth, i.e. resembling classical nano-crystalline diamond (NCD) films [3], with high crystallinity compatible with silicon on diamond chip technology. We present data from plasma diagnostics, showing HF pulsed data from optical emission spectroscopy (OES) for the CH 4 –CO 2 –H 2 gas chemistry and discuss the basic properties of the layers prepared. In comparison to the work [1] we have succeeded in suppression of re-nucleation during the growth and prepared high quality NCD films with 3–7% sp 2 carbon, depending on the growth conditions used, based on Raman measurements for layers as thin as 40 nm. © 2011 Elsevier B.V. All rights reserved. Introduction Due to its excellent properties diamond layers in the form of nanocrystalline and ultra nanocrystalline layers (NCD and UNCD) have been identified as having potential industrial uses from MEM devices to biomedical devices and to protective coatings [3–5]. From the point of view of improved material structure and properties, for typical applications, NCD is the preferred form [3]. The growth of NCD layers has been described before [3–5]. Typically the conditions for growth are a mix of H 2 and CH 4 using microwave plasma enhanced (MW PECVD) or hot filament (HF CVD) chemical vapour techniques with a substrate temperature of 600–1000 °C. To maximise the industrial potential of NCD layers it is necessary to grow them on large areas and at temperatures compatible with the substrate. Typical MW PECVD systems, with reasonable growth rates, are restricted to an area with a diameter of 15 cm and with growth temperatures above 600 °C. HF CVD systems, with reasonable growth rates, do allow for the deposition of NCD on large areas but also at temperatures above 600 °C. Therefore neither of the typical systems is attractive for industrial scale production of NCD. To overcome these restrictions the use of linear antennas has been described [1,2]. Our system further enhances this technique via the use of high frequency pulsed microwaves which is essential for the enhancement of plasma concentration due to non-linear absorption (i.e. where MW absorp- tion increases non-linearly with the power due to non-linear electron acceleration in strong microwave fields), leading to an increase in the concentration of atomic hydrogen and therefore maximising growth rates at low temperatures. The aim of this paper is to demonstrate that with the described pulsed MW system high quality NCD films have been produced using a novel pulsed deposition mode and therefore reducing the re-nucleation rate, due to intensive etching in the off- plasma periods, as compared to [1] which used continuous wave plasmas. This is the prime novelty of this work when compared to [1]. Diamond & Related Materials 20 (2011) 613–615 ☆ Presented at NDNC 2010, the 4th International Conference on New Diamond and Nano Carbons, Suzhou, China. ⁎ Corresponding author. Tel.: +420 266 052 634; fax: +420 286 890 527. E-mail address: taylor@fzu.cz (A. Taylor). 0925-9635/$ – see front matter © 2011 Elsevier B.V. All rights reserved. doi:10.1016/j.diamond.2011.01.003 Contents lists available at ScienceDirect Diamond & Related Materials journal homepage: www.elsevier.com/locate/diamond