A prevailing paradigm in the diamond industry is that diamonds can only be grown using liquid metal catalysts at high pressures and temperatures. However, a team of researchers led by Director Rod Ruoff at the Center for Multidimensional Carbon Materials (CMCM) within the Institute for Basic Science (IBS) has successfully grown diamonds under conditions of 1 atmosphere pressure and at 1025 °C using a liquid metal alloy composed of gallium, iron, nickel, and silicon, thus challenging the existing paradigm. The discovery of this new growth method opens up many possibilities for further basic science studies and for scaling up the growth of diamonds in new ways. The breakthrough was the result of meticulous experimentation and the development of a new home-built cold-wall vacuum system that greatly accelerated their parametric studies.
The team discovered that diamond grows in the sub-surface of a liquid metal alloy composed of gallium, nickel, iron, and silicon when exposed to a mixture of methane and hydrogen under 1 atm pressure at approximately 1025 °C. The initial formation of diamonds occurs without the need for seed particles, allowing the particles to merge and form a film that can be easily detached and transferred to other substrates for further studies and potential applications. The synthesized diamond film was found to have a high purity of the diamond phase and the presence of silicon-vacancy color centers, which may have applications in magnetic sensing and quantum computing.
Through a combination of experimental and theoretical approaches, the research team delved into the mechanisms for diamonds to nucleate and grow under the new conditions. The presence of silicon was found to play a critical role in the growth of diamonds, with silicon promoting the formation and stabilization of certain carbon clusters necessary for nucleation. The team also discovered that a temperature gradient in the liquid metal facilitated carbon diffusion towards the central region, promoting diamond growth. The flexibility in the composition of liquid metals also offers opportunities for further research and experimentation in diamond growth methods.
The researchers conducted high-resolution transmission electron microscope (TEM) imaging on the samples to study the growth mechanisms of diamonds in the liquid metal environment. The results showed that around 27 percent of atoms in the amorphous subsurface region directly in contact with the diamonds were carbon atoms, indicating a high concentration of carbon dissolved in the gallium-rich alloy. Time-of-flight secondary ion mass spectrometry depth profiling revealed that the concentration of carbon atoms in the subsurface region was close to supersaturation, leading to the nucleation of diamonds at around 10 to 15 minutes of exposure to methane and hydrogen.
The discovery of diamond growth in a low-pressure, low-temperature liquid metal environment presents exciting opportunities for further basic science studies and potential applications in fields such as magnetic sensing and quantum computing. The team is now exploring the timing of nucleation and growth of diamonds in this new method, as well as investigating the potential for using different liquid metal compositions and carbon precursors for diamond growth. The research was supported by the Institute for Basic Science and published in the journal Nature, showcasing the innovative approach to diamond manufacturing developed by the team.
