Coupled effect of nitrogen addition and surface temperature on the morphology and the kinetics of thick CVD diamond single crystals J. Achard ⁎ , F. Silva, O. Brinza, A. Tallaire, A. Gicquel LIMHP/CNRS, 99 av. JB Clément, 93430 Villetaneuse, France Available online 31 October 2006 Abstract In this study, homoepitaxial thick diamond films were grown by CVD at high microwave power densities for temperatures ranging from 800 °C to 950 °C and with nitrogen additions from 75 to 200 ppm relative to the total gas flow. It was observed that there is a coupled effect of these two parameters on the growth mechanisms of the CVD diamond film. For a deposition temperature close to 875 °C and for the lowest nitrogen concentration, the growth proceeded via a step flow mode identified by classical step bunching phenomena due to the presence of nitrogen and leading to the appearance of macro-steps. When nitrogen concentration was increased keeping the same temperature, the growth mode evolved from a step flow mode to a bidimensional nucleation mode, for which macro-steps are no longer observed. For higher growth temperatures (950 °C), it was found that this growth mode transition still exists but appears for much higher nitrogen concentration. These different observations, associated with the resulting growth rates, are discussed in terms of surface modification induced by the presence of nitrogen impurity. It is shown in particular that an increase of nitrogen concentration is equivalent to an increase of the surface supersaturation, this effect being compensated by an increase of the deposition temperature. © 2006 Elsevier B.V. All rights reserved. Keywords: Single crystal growth; Nitrogen; Defect characterization; Morphology 1. Introduction The progress recently achieved in the synthesis of pure and relatively thick diamond single crystals by Microwave Plasma Assisted Chemical Vapour Deposition (MPACVD) has opened the way for potentially interesting applications particularly for high power electronic devices. However, to limit the deposition time, the process should involve high growth rates (ideally several tens of microns per hour) and this can be achieved by the use of high plasma densities or by the addition of nitrogen to the gas phase [1–3]. Recently, a study performed at the lab has shown that the addition of very small amounts of nitrogen to the gas phase (less than 10 ppm) in a high microwave power process leads to a strong increase of the growth rates (by almost a factor of 3) [4], whereas the thick colourless diamond single crystals obtained exhibit high quality, acceptable for many applications. It is then of interest to further increase the nitrogen amount added to the gas phase in order to evaluate the effect on the growth kinetics and on the quality of the synthetic single crystals. Indeed, although many authors reported on the influence of large amounts of nitrogen on the growth rate and morphology of diamond [5–10], only few works have been performed at high Diamond & Related Materials 16 (2007) 685 – 689 www.elsevier.com/locate/diamond ⁎ Corresponding author. E-mail address: achard@limhp.univ-paris13.fr (J. Achard). Table 1 Growth conditions of the samples considered in the paper Samples % CH 4 Deposition time (h) T S (°C) [N 2 ] (ppm) Thickness (μm) Growth rate (μm/h) 1 4 5 800 100 155 31 2 875 75 175 35 3 100 208 41 4 150 258 52 5 200 275 55 6 950 75 150 30 7 100 186 37 8 150 215 43 9 200 251 50 0925-9635/$ - see front matter © 2006 Elsevier B.V. All rights reserved. doi:10.1016/j.diamond.2006.09.012