Carrier concentration dependence of terahertz transmission on conducting ZnO films

With the dc reactive magnetron sputtering method, conducting ZnO thin films with different carrier concentrations on glass substrate were fabricated. The dielectric responses of the ZnO films are characterized with terahertz time-domain spectroscopy. Frequency-dependent conductivity, power absorption, and refractive index are obtained, and the experimental results can be well reproduced with the classic Drude model. Our results reveal that by adjusting the carrier concentration of the ZnO film, the conducting ZnO film can serve as broadband antireflection coatings for substrates and optics in the terahertz frequency range.