Effect of transparent Pb substrates on the structural, optical, dielectric and electrical properties of copper selenide thin films

Abstract

Herein, copper selenide thin films are coated onto transparent lead substrates. Pb/CuSe stacked layers is fabricated by the thermal evaporation technique under a vacuum pressure of 10-5 mbar. They are structurally, morphologically, optically and electrically characterized. Lead substrates enhanced the crystallinity of CuSe through increasing the crystallite sizes, reducing the microstrain and lowering defect densities. In addition, a blue shift in the energy band gap associated with remarkable increase in the value of the high frequency dielectric constant resulted from replacement of glass by Pb substrates. Moreover, significant increase in the optical conductivity in the ultraviolet range of light is observed. Fitting the optical conductivity in accordance with Drude- Lorentz models allowed determining the effect of transparent Pb substrates on the plasmon frequency, scattering time at femtosecond level and drift mobility of CuSe. On the other hand, electrical measurements on the Pb/CuSe/C by imposing an ac signal of low amplitude in the frequency domain of 10-1000 MHz, have shown that the Pb/CuSe can perform as negative capacitance source employable for devices scaling and low power applications.