Dielectric properties of nitrogen-doped polycrystalline diamond films in Ka band

摘要

Diamond films could be used as a dielectric material in the field of microwave technology. However, nitrogen impurities are frequently incorporated in diamond films unintentionally and/or intentionally. In this investigation, dielectric properties of polycrystalline diamond films prepared at nitrogen concentrations of 0-40 ppm range were measured by using a split-cylinder resonator in Ka band. Quality and impurities of these nitrogen doped diamond films were characterized using Raman, photoluminescence and infrared absorption spectroscopy. Results showed that with the increase in nitrogen concentration in the deposition atmosphere, dielectric loss tangent of the diamond films revealed a complicated change behavior, and a maximum in dielectric loss tangent was observed for a diamond film prepared at an intermediate nitrogen concentration. By characterizing dielectric properties of diamond films at different temperatures and separating dielectric losses of different origins, it is reasoned that the above mentioned abnormal behavior in dielectric loss of nitrogen-doped diamond films may be explained by compensation effect of acceptor levels by nitrogen donor levels in diamond films.