Unprecedented differences in the diamond nucleation density between carbon- and silicon-faces of 4H-silicon carbides

4H-silicon carbides deposited by diamond films have wide applications in many fields such as semiconductor heterojunction, heat sink and mechanical sealing. Nucleation plays a critical role in the deposition of the diamond film on 4H-silicon carbides. Nevertheless, as a typical polar material, the fundamental mechanism of diamond nucleation on different faces of 4H-silicon carbides has not been fully understood yet. In this contribution, nucleation of diamond was performed on the carbon- and silicon-faces of 4H-silicon carbides in a direct current chemical vapor deposition device. The nucleation density on the carbon-face is higher by 2-3 orders of magnitude compared to the silicon-face. Transmission electron microscopy verifies that there are high density diamond nuclei on the interface between the carbon-face and the diamond film, which is different from columnar diamond growth structure on the silicon-face. Transition state theory calculation reveals that the unprecedented distinction of the nucleation density between the carbon-face and the silicon-face is attributed to different desorption rates of the absorbed hydrocarbon radicals. In addition, kinetic model simulations demonstrate that it is more difficult to form CH2(s)-CH2(s) dimers on silicon-faces than carbon-faces, resulting in much lower nucleation densities on silicon-faces. (C) 2019 Chinese Chemical Society and Institute of Materia Medica, Chinese Academy of Medical Sciences. Published by Elsevier B.V. All rights reserved. ; Funding Agencies|National Key Research and Development Project [2017YFE0128600]; Ningbo 3315 Innovation Team [2019A-18-C]; Science and Technology Innovation 2025 Major Project of Ningbo [2018023]; National Defense Key Laboratory Fund [6142807180511]; Innovation Funding of State Oceanic Administration [NBHY-2017-Z3]; Ningbo Industrial Technology Innovation Project [2016B10038]; 13th Five-Year Equipment Pre-research Sharing Project [E1710161]; Key Talents Senior Engineer Project of Ningbo Institute of Materials Technology and ...