Study shows new method to produce ultrahard single layer diamond in industrial applications
- Mateo Cardinal
- 2 minutes ago
- 3 min read
Graphene’s enduring appeal lies in its remarkable combination of lightness, flexibility, and strength. Now, researchers have shown that under pressure, it can briefly take on the traits of one of its more glamorous carbon cousins. By introducing nitrogen atoms and applying pressure, a team of scientists has coaxed bilayer graphene grown through chemical vapor deposition (CVD) into a diamond-like phase — without the need for extreme heat. The finding, reported in Advanced Materials Technologies, shows a scalable way to create ultrathin coatings that combine the toughness of diamond with the processability of graphene.
The work, led by Elisa Riedo, Herman F. Mark Professor in Chemical and Biomolecular Engineering, focuses on the delicate balance between two forms of carbon bonding. In ordinary graphene, carbon atoms connect through sp² bonds in a flat honeycomb arrangement, giving rise to its electrical conductivity and mechanical toughness. Diamond, on the other hand, is built from sp³ bonds in a three-dimensional network that confers exceptional hardness. Converting one to the other typically demands extreme pressure and temperature. The team discovered that nitrogen doping lowers this barrier, allowing the transition to occur at room temperature when the layers are pressed together.
To test the effect, the researchers used CVD bilayer graphene films on silicon dioxide substrates and incorporated nitrogen atoms during the growth process. They then applied mechanical pressure using a technique known as modulated nanoindentation. The nitrogen-doped bilayer films exhibited nearly twice the stiffness of the bare substrate, suggesting the formation of stronger, diamond-like interlayer bonds. By contrast, nitrogen-doped monolayer or thicker multilayer samples showed no comparable stiffening, indicating that the effect depends on both the doping and the precise bilayer structure.
Molecular dynamics simulations provided a possible explanation. The models showed that nitrogen atoms promote the formation of sp³ bonds between the two layers when they are compressed. The nitrogen atoms appear to stabilize these interlayer bonds, effectively “locking” parts of the bilayer into a more diamond-like configuration. This cooperation between chemical doping and pressure points to a previously unrecognized pathway for transforming graphene’s atomic structure.
The implications extend beyond a mere curiosity of carbon chemistry. Because the experiments used large-area graphene grown by chemical vapor deposition, the process is inherently compatible with industrial fabrication methods and wafer scale dimensions. The transformation also occurs under mild conditions, avoiding the high temperatures that typically destroy or distort 2D materials. In principle, the approach could yield ultrathin, lightweight coatings that resist wear and deformation while maintaining the advantages of graphene substrates.
Yet the work raises as many questions as it answers. The extent of the transformation remains uncertain — whether the sp³ bonding is continuous or confined to localized regions under the indenter is not yet clear. Researchers also do not know whether the diamond-like phase persists once the pressure is released, or whether it relaxes back to graphene over time. Understanding how stable and uniform these transformations are will be critical for any practical use.
The effect on electronic behavior also remains to be seen. Diamond-like carbon is typically an electrical insulator, so localized sp³ regions could alter the electronic or optical properties of the film. For device applications, the challenge will be to tune the process so that mechanical and electrical properties can be balanced rather than compromised.
Future research will need to clarify how doping levels, pressure intensity, and substrate choice influence the transformation.
The study suggests that graphene’s versatility may stretch further than expected. By manipulating its atomic environment — through doping, strain, or pressure — researchers may be able to switch between distinct structural phases on demand. Such control could lead to a new generation of adaptive materials, capable of shifting from soft to hard, or from conductive to insulating, depending on their operating conditions.
Graphene has often been described as a material with untapped potential. This work offers another glimpse of that potential, showing that even after more than a decade of intense study, carbon’s simplest form still has surprises left to offer.
Reference Pressure and Nitrogen Induced Phase Transition in Bilayer CVD Graphene
Nitika Parashar, Ryan Khan, Daniel Enrique Vizoso, Wujoon Cha, Yanxiao Li, Martin Rejhon, Carrie Donley, Dudley Finch, Rémi Dingreville, Carmela Aruta, Elisa Riedo
