Dielectric properties of single crystalline diamond wafers with large area at microwave wavelengths

• Dielectric properties of large size diamond wafers were studied for the first time.
• Dielectric tanδ of them were found to be as low as ≲ 2 × 10− 5.
• This indicates the potential in windows for microwave injections with high energy.

In this paper, we present first measurements, carried out at microwave wavelengths, aiming to characterize the dielectric properties of large size single crystalline diamond (SCD) wafers. While the sizes of the SCD wafers are still not sufficient for practical use, we obtained good optical property results. The sample with both sides polished shows a dielectric loss tangent tanδ as low as or possibly lower than a polycrystalline diamond sample with high quality. Results show the importance of surface treatment, especially on the boundaries of the composed SCD chips even without any graphitic component in the diamond wafers.