Dielectric Properties and Applications of CVD Diamonds in the Millimeter and Terahertz Ranges

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

“…As a reference, the tanδ measurements performed on the polycrystalline, surface polished, sample in the hemi-spherical resonator showed a loss tangent in the order of 10 −5 (Fig. 3b), which is comparable to the current state of the art [24][25][26]. Theoretically the polycrystalline samples suffer from the bulk losses given by sp 2 bonds between the single crystals [27,28].…”

Measurement of the complex permittivity of polycrystalline diamond by the resonator method in the millimeter range

“…The differences in tan δ observed during the rotation of the sample (see Table 2) can result from the inhomogeneity of the material: both more and less transparent subsurface areas can come into the field antinode. The values obtained at the frequency f = 27 GHz are about two orders of magnitude larger than the loss tangent for the quality polycrystalline diamond plates in the frequency range of 170 to 200 GHz [1], which is not surprising because losses should increase with decreasing frequency as tan δ ∼ 1/f if they depend on inclusions of conducting phases (amorphous carbon) [11]. However, when comparing with the results for the disc-shaped polycrystals [1], one should bear in mind that in the case of rods the contribution to the losses comes not only from the subsurface defects in the laser cut plane but also from the highly defective small-grain layer on the substrate side, which is usually polished out in the process of making diamond windows.…”

“…Polycrystalline diamond synthesized from the gas phase (CVD diamond) is highly appropriate for these applications due to a combination of several favorable factors: high transparency in the above frequency range, record high heat conduction (up to 2000 W mK −1 ), high mechanical strength, and low permittivity [1,2]. The loss tangent tan δ for diamond at frequencies of 100 to 200 GHz can be as low as 10 −4 to 10 −5 and even lower [2].…”

Doomed Couple of Diamond with Terahertz Frequency: Hyperfine Quality Discrimination and Complex Dielectric Responses of Diamond in the Terahertz Waveband

“…Furthermore, the main loss of PCD at MM waves is believed to be due to extrinsic conductivity, which has an inverse frequency dependence, tan δ ∝ 1/ f . However, Garin and Mocheneva found that it is impossible to extract the pure 1/ f dependence. The concentration of shallow levels, especially the extremely shallow levels (meV) induced by native defects and/or sp 2 -like atoms located at GBs with dangling bonds, is significantly higher in poor quality diamond, which results in a monotonous decrease of the permittivity with frequency increasing. , They also proposed that a scattering mechanism exists over 0.2 THz, which results in the tan δ growth.…”