Influence of photoelectric parameters for AZO transparent conductive films on electromagnetic scattering characteristics

Al-doped zinc oxide (AZO) transparent conductive films with different sheet resistances were deposited on the surface of float glass by a room temperature coating technique. The procedure for radar cross section (RCS) measurements for AZO transparent conductive films was established, and the definition of the relative reflectivity based on the RCS mean value was proposed. The electromagnetic scattering characteristics for the AZO transparent conductive films were analyzed by way of the sheet resistance and visible light transmittance. The AZO films with different sheet resistances were tested in the microwave darkroom and RCS curves for the films were obtained with incident frequencies of 10 GHz and 15 GHz and in the HH and VV polarizations modes. The characteristics of the RCS curve distribution in angular domains of 20° and 60° in the nose direction and the characteristics of RCS mean values were analyzed to study the stealth performance for aircraft cockpit glasses. The influence of the sheet resistance on RCS relative reflectivity and visible light transmittance was studied based on RCS test results from the AZO transparent conductive films. When the sheet resistance was small, the distribution of the RCS curves was similar to that of their corresponding metal. When the sheet resistance increased, the RCS mean values in the angular domains of 20° and 60° in the nose direction decreased and the stealth performance was reduced. In addition, the RCS relative reflectivity decreased and the visible light transmittance increased. The rate of the decrease in the relative reflectivity was related to the sheet resistance. It was determined that an appropriate sheet resistance can meet the needs of stealth and lighting simultaneously. The results achieved from darkroom test also proved that upon meeting the requirement of visible light transmittance for aircraft cockpit glasses, the AZO transparent conductive film could provide shaped stealth performance when the value of sheet resistance was between 18 Ω to 45 Ω. When the sheet resistance was 18 Ω, the best performance of AZO appears with a relative reflectivity, Re_m² of 84% and Re_dB of 0.73 dB.