The Effects of Methane Concentration on Diamond Nucleation and Growth During Bias Enhanced Nucleation on 3C-SiC(100) Sur
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0956-J08-03
The Effects of Methane Concentration on Diamond Nucleation and Growth During Bias Enhanced Nucleation on 3C-SiC(100) Surfaces Jean-Charles Arnault1, Samuel Saada2, Luciana Intiso1, and Philippe Bergonzo2 1 DSM/DRECAM/SPCSI, CEA Saclay, bâtiment 462, Gif sur Yvette, 91191, France 2 LIST/SSTM/DETECS/LTD, CEA Saclay, bâtiment 451, Gif sur Yvette, 91191, France
ABSTRACT The effects of methane concentration on the nucleation and growth of diamond during bias enhanced nucleation treatment was studied on 3C-SiC (100) surfaces. At low methane concentration of 1%, no diamond nucleation was observed, whereas at 3 %, nucleation density values as high as 4x1010 / cm2 were reached. Increasing further the methane concentration to 5% induced a slight but significant enhancement of the diamond nucleation density, which in this case was measured to be 7 x1010 / cm2. Moreover, Field Emission Gun Scanning Electron Microscopy (FEG-SEM) pictures emphasized clearly that the methane content also affects the growth mechanisms. INTRODUCTION Bias enhanced nucleation (BEN) is a powerful treatment to provide high enhancements of diamond nucleation density with values up to 1011 / cm2 on silicon [1]. Moreover, this treatment allows the growth of highly oriented diamond films on silicon, cubic silicon carbide as well as iridium substrates [2-4]. Encouraging progresses have been performed towards highly oriented diamond film preparation on 3C-SiC surfaces [5]. Although the BEN effects have been extensively studied on silicon, only a few studies were reported on 3C-SiC surfaces [3, 6]. The aim of this paper is to focus on the role methane plays in the nucleation and growth of diamond particles during the BEN step. An in situ surface study was carried out. The experiments were performed in a Microwave Plasma Chemical Vapor Deposition (MPCVD) reactor connected to an UHV analysis chamber using X-ray Photoelectron (XPS) and X-ray Auger Electron (XAES) Spectroscopy. Diamond deposits were then characterized ex situ using Field Emission Gun Scanning Electron Microscopy (FEG-SEM). EXPERIMENTAL Single domain n-type 3C-SiC thin films epitaxially grown on a Si (100) substrate (3° off axis) were used. Plasma treatments were performed in a home designed MPCVD reactor, equipped with a 2.45GHz – 2kW SAIREM microwave generator. The base pressure inside the chamber was approximately 1·10-9 mbar. The sample holder was placed onto a molybdenum disk in order to minimize residual contamination from the support during the plasma discharge. High purity research grade gases were used: N55 for methane and N90 for hydrogen (with a catalytic purifier added to the gas line). Each 3C-SiC sample underwent two successive CVD steps. In the
first step, the surfaces were exposed to a H2 / CH4 mixture for 10 minutes to stabilize the plasma parameters and the substrate temperature. Three samples were prepared using the different methane concentrations of 1, 3 and 5%. All the other CVD parameters were identical (Table 1). In the second step (nucleation), a negative bi
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