Low temperature, pressureless sp2 to sp3 transformation of ultrathin, crystalline carbon films

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).

Diamane: design, synthesis, properties, and challenges

“…Nevertheless, Raman spectroscopy is an indirect method to detect sp 3 carbon bonds, and the single-point measurements cannot determine hydrogen position bounded either to the surface of the layer or only to the edge. To prove that graphene forms the interlayer sp 3 bonds, more direct evidence is needed in future [48]. Hydrogenation of graphene could be also achieved by the hot filament process at nearly ambient conditions.…”

“…Hydrogenation of graphene could be also achieved by the hot filament process at nearly ambient conditions. The hot filament process can effectively generate hydrogen atoms [43,48,49] and avoid ion acceleration damage to the graphene sample. Experimentally, FLG can be grown on Pt(111) by chemical vapor deposition, and then, HD can be prepared by chemical adsorption of carbon atoms on the graphene surface with deuterium atoms produced by the hot wire process [43].…”

“…The hot filament process can also realize the double-sided hydrogenation of graphene. However, due to the difference in the number of layers and stacking patterns during the preparation of graphene, the hydrogenated products were found to be a variety of mixtures of diamane checked by Raman spectroscopy and Fourier transform infrared (FTIR) microscopy [48].…”

“…The main contribution of thermal conductivity comes from out-of-plane acoustic phonon modes in HD to optical modes in FD. Diamane also exhibits great stiffness and it would make diamane very attractive for ultrathin protective coatings, for example, used for aerospace equipment as ultrahigh-strength components in composite materials [48]. In addition, recent studies on the vibrational properties of diamane nanoribbon (DNR) showed that DNR resonator possesses a high natural frequency and a large quality factor (Q-factor) [23].…”

Modifying Electronic and Elastic Properties of 2-Dimensional [110] Diamond by Nitrogen Substitution

“…Several works have theoretically studied on the stability of diamane that is passivated by other atoms and molecules and also its band gap and thermal conductivity, depending on passivating molecules [15,16]. The diamane can be synthesized by exposing a bilayer graphene in order to chemically react with H or F atoms [17][18][19][20].…”