▎ 摘　　要

Hot-filament process was recently employed to convert, totally or partially, few-layer graphene (FLG) with Bernal stacking into crystalline sp(3)-C layers at low pressure. The result reported earlier relies on Raman spectroscopy and Fourier transform infrared microscopy. As soon as the number of graphene layers in the starting FLG is higher than 2-3, the sp(2)-C to sp(3)-C conversion is partial only, due to the prevalent Bernal stacking sequence. We report new evidences confirming the sp(2)-C to sp(3)-C conversion from electron diffraction at low energy, Raman spectroscopy and Density Functional Theory (DFT) calculations. Partial sp(2)-C to sp(3)-C conversion generates couples of twisted, superimposed coherent domains (TCD), supposedly because of stress relaxation, which are evidenced by electron diffraction and Raman spectroscopy. TCDs come with the occurrence of a twisted bilayer graphene feature located at the interface between the upper diamanoid domain and the non-converted graphenic domain underneath, as evidenced by a specific Raman signature consistent with the literature. DFT calculations show that Raman T peak originates from a combination of the sp(3)-C stretching mode of a sp(3)-C layer with the optical out-of-plane mode of a graphene layer; both layers being sandwiched between a highly hydrogenated sp(3)-C surface and the underneath unconverted graphene layer(s). (C) 2019 Elsevier Ltd. All rights reserved.