Diamond Foundry announced on November 5, 2026, that it has successfully produced a single-crystal diamond 200mm in diameter. The company says this is the first time a single-crystal diamond of this size has been made. The diameter is double that of the 100mm product announced in 2023. However, the photo released shows an unpolished, as-grown piece, and shipments of 200mm substrates processed to a state suitable for semiconductor manufacturing have not begun.
What matters about this result is not simply that a large diamond was made. Diamond Foundry's announcement is not about small crystals bonded together, nor about polycrystalline diamond made of many crystal grains, but about a single crystal whose structure is continuous across the full 200mm diameter. Single-crystal diamond combines extremely high thermal conductivity with electrical insulation, and it is expected to serve as a heat-dissipation material for AI semiconductors and other chips whose heat output keeps rising.
From 100mm to 200mm: Four Times the Area in Theory
In October 2023, Diamond Foundry announced a single-crystal diamond wafer 100mm in diameter and weighing 110 carats. The new 200mm product doubles that diameter. Comparing them as circular materials, the area grows about fourfold, from roughly 78.5 cm² to roughly 314 cm².
This larger size has practical significance for semiconductor manufacturing. Because conventional single-crystal diamond was limited in size, there were constraints when cutting out heat-dissipation components for large semiconductor chips or processing multiple components at once. A larger source area could make it possible to obtain more components of the same size.
That said, a fourfold increase in area does not necessarily mean a fourfold increase in usable components. The usable area depends on the removal of the crystal's outer edge, material lost during polishing, the distribution of defects, and other factors. The announcement did not disclose details such as the effective diameter after processing, in-plane defect density, or yield.
200mm is also the same diameter as the 8-inch wafers widely used in the semiconductor industry, making it an important milestone for combining single-crystal diamond with existing semiconductor manufacturing technology. Even so, matching the material's size does not mean that processes and equipment designed for silicon can be used as they are.
Hopes for Cooling AI Chips, but Thermal Conductivity Alone Doesn't Decide the Outcome
Diamond Foundry puts particular emphasis on cooling high-performance semiconductors. In AI GPUs and similar chips, large amounts of power are concentrated in a limited chip area, creating localized hot spots. Keeping the temperature of these areas down is essential for maintaining performance and reliability.
Diamond has higher thermal conductivity than copper or silicon, making it an excellent material for spreading heat to its surroundings. Its high electrical insulation also makes it a promising heat-dissipation component to place close to a semiconductor chip. Diamond Foundry aims to incorporate single-crystal diamond into semiconductor substrates and cooling structures to improve the performance and reliability of chips with high heat density.
However, a material's thermal conductivity is not the same as the cooling performance of a finished semiconductor package. If the thermal resistance of the bonding layer between the chip and the diamond is high, the material's inherent performance cannot be fully exploited. And even if diamond spreads heat efficiently, temperature reduction is limited if the cooling mechanism that ultimately removes that heat is inadequate.
Therefore, the successful production of the 200mm diamond cannot be interpreted as a result that directly lowers AI chips' operating temperatures or reduces their power consumption. To judge the actual effect, it would be necessary to use the same chip, bonding conditions, and cooling mechanism, and compare how much the temperature distribution and thermal resistance change with and without diamond.
25 Years of Research, With 300mm as the Next Goal
This result draws on many years of research into crystal-growth technology. According to Diamond Foundry, Stefan Gsell and Martin Fischer have spent about 25 years researching technology for growing large, high-quality single-crystal diamond. They joined the company in 2022 when Diamond Foundry acquired Augsburg Diamond Technology, combining the crystal-growth technology they had built up with the company's manufacturing facilities and development organization.
Producing the 200mm diamond required technical development across many areas, including plasma control, the chemical reactions during crystal growth, reactor design, temperature management, and measurement technology. Diamond Foundry CEO Martin Roscheisen describes the achievement as the fruit of long-term research and the efforts of many engineers.
Roscheisen indicated that realizing the 200mm product has also put a 300mm single-crystal diamond within sight. However, this is his technical outlook, not an announcement that a 300mm product has been successfully made or that mass production has begun. For the 200mm product, too, the timing of mass production, pricing, and supply terms for customers have not been disclosed.
The announcement is an important manufacturing advance in scaling up single-crystal diamond. At the same time, judging its practicality as a semiconductor material will require confirming the quality of the substrate after processing, manufacturing cost, the volume that can be supplied reliably, and the cooling performance once it is built into actual chips. The key question going forward is whether the 200mm crystal size can be turned into the quality and productivity needed for commercial semiconductors.