Diamond Foundry says it has produced the world’s first 200-millimeter (7.9-inch) single-crystal diamond, a development that could bring one of nature’s most thermally conductive materials closer to semiconductor manufacturing. The San Francisco-based company announced the milestone on November 6, describing it as the culmination of a 25-year effort to grow large, continuous diamond crystals.The achievement is significant because diamond offers a combination of properties that could address some of the challenges facing advanced electronics, particularly the growing difficulty of removing heat from high-performance processors. However, the company has so far shown the new crystal in its as-grown, unpolished state. The 200 mm crystal is a single continuous structure, rather than a collection of smaller diamonds joined together or a polycrystalline disk containing multiple crystal grains. That distinction matters because grain boundaries and defects can affect how efficiently heat and electrical charge move through a material.Why growing a large single crystal is difficultDiamond is made up of carbon atoms arranged in a tightly ordered crystal lattice. Producing a large single crystal requires maintaining that atomic arrangement across the entire material as it grows. Even small inconsistencies can introduce defects that undermine the properties manufacturers want to preserve.Conventional high-pressure, high-temperature methods can produce synthetic diamonds, but scaling them to semiconductor-sized single crystals presents substantial engineering challenges. Chemical vapor deposition (CVD), which grows diamond from a carbon-containing gas in a controlled environment, offers another route. Microwave plasma CVD is particularly important in research into large, high-quality diamond crystals.Diamond Foundry’s earlier milestone provides some context. The company then announced a 100 mm (3.9 inches) single-crystal diamond wafer produced using diamond heteroepitaxy, a technique that grows a crystal on a different underlying material while encouraging it to adopt an ordered diamond lattice. The company has not disclosed whether the newly announced 200 mm crystal uses precisely the same process.According to CEO Martin Roscheisen, the latest achievement required advances in plasma physics, reactor engineering, growth chemistry, crystal engineering and manufacturing controls. He also credited Stefan Gsell and Martin Fischer, whose work on scaling single-crystal diamond began 25 years ago.Why the semiconductor industry is interested in diamondOne of diamond’s most attractive properties is its exceptional thermal conductivity. High-purity single-crystal diamond can conduct heat at roughly 2,000 watts per meter-kelvin (W/m·K) at room temperature, several times the thermal conductivity of copper.That capability could make diamonds useful for managing heat in increasingly powerful electronic devices. Modern AI processors and high-performance computing systems concentrate substantial electrical power into relatively small areas. Localized heat buildup can limit operating performance, increase cooling requirements, and accelerate component degradation.Diamond could serve as a heat spreader or substrate in advanced chip packages, helping move heat away from hotspots. Its wide bandgap of approximately 5.47 electron volts also makes it a candidate for high-power and high-frequency electronics that must operate under demanding electrical conditions.However, diamond is not yet a straightforward replacement for silicon. Manufacturing electronic devices from it remains difficult, particularly because reliably controlling its electrical properties through doping is challenging. Integrating diamond with existing semiconductor materials and manufacturing processes also requires further development.A milestone, not yet a production-ready waferThe distinction between growing a large crystal and manufacturing a usable semiconductor wafer is important. The first D200mm sample shown by Diamond Foundry is unpolished and directly from the growth process. It will need further processing and characterization before its suitability for chip manufacturing can be established.Manufacturers must achieve consistent thickness, surface flatness, low defect density and reliable electrical and thermal properties across the usable wafer area. They must also demonstrate repeatability across multiple production runs and establish that the material can be integrated into device fabrication.Diamond Foundry says the 200 mm achievement makes a future 300 mm (11.8 inches) crystal predictable, although it has not provided a timeline or detailed manufacturing data for that next step.The company is also expanding its manufacturing ambitions through a planned $2.77 billion project in Spain supported by the European Chips Act. Its broader goal is to turn single-crystal diamond into an industrial semiconductor material rather than a specialty product available in limited dimensions.