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.

Effects of Si Slabs on the Performance of CdO Thin Films Designed for Optoelectronic Applications

“…In another work, the nanosandwiching of indium between two layers of copper oxide and gallium sulfide was able to engineer the energy band gap and to enhance the dielectric performance of the gallium sulfide thin films 8 . In the same context, insertion of YAu alloy of thickness of 140 nm between two layers of ZnSe 9 successfully increased the drift mobility in the ZnSe thin films from 1098 to 1766 2 / cm Vs. The plasmon frequency in ZnSe was also shifted from 0.94 to 2.13 GHz upon nanosandwiching.…”

“…=10.98% 9 . Large lattice mismatches between the layers results in high defect density which enables CdO/Si/CdO films to be used for producing a highly efficient light emitting diodes 9 .…”

“…Figure 4a displays the real part of the dielectric ( r ε ) spectra for the stacked layers of CdO. The dielectric constant spectra are calculated from the measured transmittance and reflectance spectra with the help of Fresnel's equations for light at normal incidence 9 . Significant enhancement in the dielectric constant value is observed upon insertion of Si layers between stacked layers of CdO.…”

“…To give significance for the observed ( ), σ ω the experimental conductivity spectra are theoretically reproduced with the help of Drude-Lorentz model for optical conduction. In that model, the conductivity is given by 8,9,37…”