Yan-Kun Dou

The enhanced polarization relaxation and excellent high-temperature dielectric properties of N-doped SiC

The dielectric properties and microwave attenuation performance of N-doped SiC have been evaluated in 8.2–12.4 GHz in the temperature range of 293–673 K. The N doping dramatically improves the microwave absorption capability of SiC. The minimum reflection loss of N-doped SiC is enhanced to nearly −30 dB with the effective absorption bandwidth [RL(dB) ≤ −10 dB] up to 3 GHz at 673 K. The excellent high-temperature dielectric properties are attributed to multi-relaxations, originated from the polarization relaxations of dipoles induced by the N doping and vacancy defects.

Numerical Study of an A-Shape Negative Refractive Index Material

Metamaterial designing is an important issue in order to reduce the complexity and for the extensive use in various potential applications. This paper presents an A-shape novel metamaterial structure which simultaneously exhibits negative permittivity and negative permeability. An electromagnetic wave simulation is performed, and the results show that the proposed metamaterial unit cell is capable of achieving a negative refractive index. Furthermore, a left hand prism was designed composed of metamaterial unit cells. Simulation of the left hand prism proves the presence of a negative refractive index. The proposed design is easy to fabricate compared to the complex structures, due to the simple geometry, and could be used in various applications.

Enhanced photoconductivity of 3C-SiC by Al/N codoping

In order to enhance the photoconductivity of 3C-SiC by high Al doping, the Al/N codoping has been investigated using the first principles calculation. Several structural models were constructed, i.e., Al1/N, Al2/N, Al3/N, and Al4/N. Structural stability and electronic property of Al/N codoped 3C-SiC with different models were studied. It is found that the adjacent pair of Al and N in 3C-SiC is energetically favorable, and the structure of Al/N codoped 3C-SiC is more stable than that of the mono Al doped 3C-SiC. The results indicate that the N incorporation facilitates the substitution of Al for Si in 3C-SiC. The mono doping of Al can cause the band gap decrease by 82 meV. However, the codoping of Al and N can further narrow the band gap by 167 meV. Photoconductivity calculation shows the photoconductivity of the Al/N codoped 3C-SiC is higher in the range from near infrared to ultraviolet wavelength in comparison with the intrinsic 3C-SiC. The calculated intrinsic absorption edge of Al/N codoped 3C-SiC sho...