A research team led by Rod Ruoff at the Institute of Basic Science (IBS) at the Ulsan National Institute of Science and Technology (UNIST) in South Korea has unveiled a groundbreaking method for producing lab-grown diamonds without the need for extreme pressure.
This innovative approach holds promise for synthesizing larger-sized diamond crystals and extended films, with wide-ranging applications in optics and advanced electronics, according to the researchers.
While lab-grown or artificial diamonds are not a novel concept, General Electric pioneered this technique nearly five decades ago using molten iron sulfide. The High-Pressure, High-Temperature (HPHT) method mimics the natural conditions found in the Earth’s mantle, where diamonds form naturally. Under temperatures reaching 2552 degrees Fahrenheit (1400 degrees Celsius) and pressures of at least five gigapascals, liquid metal transforms into diamonds.
Another approach, chemical vapor deposition (CVD), requires less pressure but demands specialized semiconductor fabrication equipment to carry out the process. Both methods utilize a diamond seed to initiate diamond formation. However, the UNIST team’s approach eliminates this requirement and operates at normal atmospheric pressure.
The Genesis of a New Method
Years ago, Ruoff speculated that diamond synthesis might not necessitate high pressures. A study in 2017 revealed that liquid gallium could dissolve carbon atoms and bind them into a solid sheet-like graphene when exposed to methane gas.
Building on this insight, Ruoff and his team began exploring whether this process could also yield diamonds. Initial experiments involved adding droplets of molten gallium and other metals, exposing the mixture to carbon-related gases. Serendipitously, when a blob of molten gallium spilled over a layer of pure silicon and dissolved it, the researchers discovered a collection of tiny diamond crystals within the solidified metal.
Refinements in the method led to a precise recipe involving a blend of liquid gallium, silicon, iron, and nickel heated in a small crucible to 1877 degrees Fahrenheit (1025 degrees Celsius) and exposed to methane and hydrogen gases. This process, which does not require a diamond seed, results in the formation of diamond-like structures.
Accelerating the Process
In earlier experiments, the researchers utilized a large chamber known as RSR-A, with an interior volume of 26 gallons (100 liters). However, to ensure effective exposure to methane and hydrogen gases, the chamber had to undergo a series of steps involving the evacuation of air, filling with inert gas, and subsequent vacuuming before the gas mixture could be introduced at the required atmospheric pressure. This process took approximately three hours before the experiment could commence.
To streamline the procedure, Ruoff devised a solution: reducing the chamber’s volume. Thus, the team built a new chamber, RSR-S, with an interior volume of just over two gallons (nine liters). With this modification, the entire process can now be completed in a mere 15 minutes.
While the research is still in its early stages, it sets the stage for the production of thin diamond films that could find applications in quantum computers, magnetic sensors, high-power electric devices, radiation detectors, and lasers in the future, as stated in the press release.
