No abstract

Nanosized and crystalline sp 3-bonded carbon materials were prepared over large surface areas up to ~33x51 m 2 from the exposure of few-layer graphene (FLG) to H radicals produced by the hotfilament process at low temperature (below 325 C) and pressure (50 Torr). Hybrid materials were also obtained from the partial conversion of FLG. sp 3-C related peaks from diamond and/or lonsdaleite and/or hybrids of both were detected in UV and visible Raman spectra. C-H bonding was directly detected by Fourier Transform Infrared (FTIR) microscopy over an area of ~150 m 2 and one single component attributed to sp 3-C-H mode was detected in the C-H stretching band showing that carbon is bonded to one single hydrogen and strongly suggesting that the sp 3-C materials obtained are ultrathin films with basal planes hydrogenated. The experimental results are compared to computational predictions and comprehensively discussed. Those materials constitute new synthetic carbon nanoforms after fullerenes, nanodiamonds, carbon nanotubes and graphene. This opens the door to new research in multiple areas for the development of new potential applications and may have wide scientific impact, including for the understanding of extraterrestrial diamond-related structures and polytype formation mechanism(s).

Hot-filament process was recently employed to convert, totally or partially, few-layer graphene (FLG) with Bernal stacking into crystalline sp 3 -C sheets at low pressure. Those materials constitute new synthetic carbon nanoforms. 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 tends to be partial only. We hereby 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 diamanoïd domain and the non-converted graphenic domain underneath, as evidenced by a specific Raman signature consistent with the literature. DFT calculations show that the up-to-now poorly understood Raman T peak originates from a sp 2 -C-sp 3 -C mixt layer located between a highly hydrogenated sp 3 -C surface layer and an underneath graphene layer.

Diamane was prepared from the exposure of bi-layer graphene to H radicals produced by the hot-filament process. A sharp sp 3 -bonded carbon stretching mode was observed by UV Raman spectroscopy while no sp 2 -bonded carbon peak was simultaneously detected. This is the first time that Raman spectra of genuine diamane are reported, which, meanwhile, are the very first evidence for the successful synthesis of genuine diamane. First principle calculations support possible full hydrogenation and confirm the hydrogenated AB configuration to be the most stable one. We believe those results constitute a milestone in the path towards the synthesis of high-quality diamane and open the door to large-scale production. Genuine diamane consists of two crystalline sp 3 −bonded carbon layers for which half of the carbon atoms are hydrogenated while the other half bond the two layers to each other [1,2]. The material stability was first predicted by Chernozatonskii et al in 2009 [1]. The increasing interest in this new 2D wide bang-gap semiconducting material comes, in particular, from its potential use in electronics [3]. Recently, the synthesis of stable 2D nanometer-thick and crystalline sp 3 -bonded carbon, was unambiguously shown for the first time [2,4]. This breakthrough was achieved from

The microstructure of distributed electron cyclotron resonance plasma-deposited hydrogenated amorphous carbon films (a-C:H) was investigated using electron diffraction, Raman spectroscopy, and Fourier transform infrared spectroscopy. Experimental evidence of the existence of transpolyacetylene (TPA) chains in a-C:H films free of nanocrystalline diamond is presented. The values of the mean bond angles and lengths and first neighbor numbers are consistent with the TPA data. The Raman spectra were fitted using the G and D bands and the bands centered at 1140, 1233, and 1475 cm(-1) assigned to TPA chains modes. The relative intensity of the latter decreases while hydrogen content decreases. A significant sp(2)-CH olefinic mode contribution to the infrared stretching band is observed for the low-density films (similar to1.2 g/cm(3)). TPA chains growth is enhanced when ion current density and energy decrease. (C) 2003 American Institute of Physics. (DOI: 10.1063/1.1538349