Forget Billions of Years: Scientists Create Diamonds in Only 150 Minutes

You may have heard that these days, about 99% of all synthetic diamonds are made using the HPHT method. [2]It is generally assumed that diamond formation is achievable just with liquid metal catalysts at pressures of gigapascal scale, usually 5-6 GPa, where 1 GPa is approximately 10,000 atmospheric pressure, with a temperature range of 1300-1600°C. Nonetheless, those diamonds treated with HPHT are always small, with a maximum weight of roughly one cubic centimeter because of the constituent parts. Which is to say—to attain such superb pressures one needs to work at a reasonably small length.

Finding out how diamonds could be made in liquid metal under conditions that are relatively less extreme (especially in terms of pressure) is an exciting basic science question that, assuming a successful solution, would transform the way diamonds are produced.

Is it possible to question the dominant narrative?This is contrary to the previous paradigm, and was achieved by a team of researchers led by Director Rod RUOFF at the Center for Multidimensional Carbon Materials (CMCM) within the Institute for Basic Science (IBS), with contributions from graduate students at the Ulsan National Institute of Science and Technology (UNIST) who have successfully grown diamonds under 1 atmosphere pressure and at 1025 °C by utilizing a liquid metal alloy constructed of This new ways of synthesizing diamonds offers many opportunities for further fundamental research and for up-scaling the growth of diamond in other ways.

This groundbreaking innovation was achieved through human creativity, relentless work, and the collaboration of many team members A series of experiments were performed where the team of researchers led by Ruoff had to carry out several hundred changes of parameters and employ various experimental approaches before they were able to synthesize diamonds utilizing a cold-wall vacuum system constructed in their home.

According to Ruoff, their previous work consisting of parametric studies was limited by the duration taken to prepare the chamber. It involved evacuating air from it, followed by flushing with an inert gas, and then evacuation to a vacuum before refilling it with a hydrogen/methane combination . This alone took over 3 hours before the actual experiment could start. In response to this problem, Dr. Won Kyung SEONG was requested to construct the much smaller chamber that cut down the time to set up and perform the experiment.

The new chamber, named RSR-S, which had the interior volume of only 9 liters, could be prepared in 15 minutes at best. This facilitated the parametric studies and culminated in the determination of the conditions in which the diamond forms in the liquid metal. The team identified that diamond formation took place in a particular subsurface layer of a liquid metal alloy made of gallium, nickel, iron and silicon when interacted with methane and hydrogen pressures of 1 atmosphere and a temperature of about ~1025 °C.

Yan GONG, an UNIST graduate student and first author, said “One day with the RSR-S system when I ran the experiment and then cooled down the graphite crucible to solidify the liquid metal, and removed the solidified liquid metal piece, I noticed a ‘rainbow pattern’ spread over a few millimeters on the bottom surface of this piece. We have discovered that the rainbow colors are diamonds! ’ By observing this phenomenonIn the first phase, there is no use of diamond or other seed particles which is required in HPHT and chemical vapor deposition synthesis methods.

After the formation of the diamond particles, they combine to form a film that can be peeled off and reused on other substrates for further analysis and usages. The synchrotron two-dimensional X-ray diffraction measurements further supported the synthesis of a diamond film with a very high purity of the diamond phase.

Another interesting feature is that silicon-vacancy color centers exist in the diamond structure, where an intense zero-phonon line is at 738. Thus, the FWHM of 5 nm in the photoluminescence spectrum when excited by a 532 nm laser was determined. Coauthor Dr. Meihui WANG adds, “This synthesized diamond with silicon-vacancy color centers may be used in magnetic sensing and quantum computing. ”The research team explored various mechanisms that would enable diamonds to nucleate and grow under these new conditions.

The cross-sectional TEM imaging of the samples revealed approximately 30-40 nm amorphous subsurface layer of the solidified liquid metal in direct contact with the diamonds. Coauthor Dr. Myeonggi CHOE observes, “It is also interesting to note that the carbon density is 27% of the atoms at the top surface of this amorphous region with progressive decrease with depth. ”

Ruoff further explains, “It may be surprising to find such a high concentration of carbon ‘dissolved’ in a gallium-rich alloy because earlier findings indicated that carbon is insoluble in gallium, The fact that this layer is amorphous whereas the rest of the sample where the liquid metal has solidified is crystalline might be a reason why this area is so unique, this is where our diamonds nucleate and so we concentrated ourEarly attempts to study the interaction of the Ga-Fe-Ni-Si liquid metal alloy were made by exposing the metal droplet to the methane/hydrogen gas mixture for short durations of time in attempts to capture the early growth state, long before a continuous diamond film could form. They further explored the carbon density profiles of subsurface areas by TOF-SIMS depth profiling.

No particles were observed after the run, only about 65 at% of carbon atoms were disengaged in the space where the diamond forms. Diamond particles started appearing at 15 min run and below were the subsurface C atom conc of about 27 at%. According to Ruoff, “The experienced subsurface carbon atoms density is high at around 10 minutes that makes the exposure close to or at supersaturation making it possible for the formation of diamonds either at 10 minutes or at sometime in-between the 10 and 15 minutes given that nucleation will happen at 10 or sometime between 10 and 15 Since particulate diamond formation occurs at the subsurface, particle growth must happen rapidly afterTwenty seven different points in the liquid metal was sensed for temperature using an addition to the growth chamber which had an array of nine thermocouple that was designed and built by Seong.

The study also showed that the central part of the liquid metal inside the chamber was slightly cooler compared to the other parts. This brings us to believe that the above temperature gradient is what is at work in allowing carbon diffusion towards the center in order to grow the diamond.

They also found that silicon is essential to this new growth of diamond that has been established by the team. With the increase in the concentration of silicon in the alloy from the optimal value, the size of the grown diamonds becomes small and their density becomes high. Diamonds could not be grown at all without the inclusion of silicon which may imply that silicon plays a role in nucleation stages of diamond formation. This was accompanied by the various theoretical calculations performed to reveal what factors that may be behind the growth of diamonds in new liquid metal phase. Some researchers indicated that silicon enhances the formation and stabilization of specific carbons through creating mostly sp3 bonds as seen with carbons.

It is suggested that clusters of carbon containing Si atoms may be the ‘pre-nuclei’ and one or more of them may grow to become a nucleus for the formation of a diamond. The fact for that is expected that the most probable range of an initial nucleus is about twenty to fifty C atoms. Ruoff further gives his opinion on this by saying that, “Our finding nucleation and growth of diamond in this liquid metal is fascinating and there are many more scientific opportunities for this finding.

We are now investigating when the nucleation occurs and therefore the subsequent rapid growth of the diamond. Some of the other promising experiments that we are focusing on include ‘temperature drop’ experiments where there is achievement of supersaturation of carbon and other needed elements and then

The team discovered their growth method offers significant flexibility in the composition of liquid metals. Researcher Dr. Da LUO remarks, “Our optimized growth was achieved using the gallium/nickel/iron/silicon liquid alloy. However, we also found that high-quality diamond can be grown by substituting nickel with cobalt or by replacing gallium with a gallium-indium mixture.” Ruoff concludes, “Diamond might be grown in a wide variety of relatively low melting point liquid metal alloys such as containing one or more of indium, tin, lead, bismuth, gallium, and potentially antimony and tellurium—and including in the molten alloy other elements such as manganese, iron, nickel, cobalt and so on as catalysts, and others as dopants that yield color centers.

And there is a wide range of carbon precursors available besides methane (various gases, and also solid carbons). New designs and methods for introducing carbon atoms and/or small carbon clusters into liquid metals for diamond growth will surely be important, and the creativity and technical ingenuity of the worldwide research community seem likely to me, based on our discovery, to rapidly lead to other related approaches and experimental configurations.

There are numerous intriguing avenues to explore!”

This research was supported by the Institute for Basic Science and has been published in the journal Nature.

Reference: Gong, Y., Luo, D., Choe, M. et al. Growth of diamond in liquid metal at 1 atm pressure. Nature (2024). DOI: 10.1038/s41586-024-07339-7

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