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Article Citation - WoS: 4Citation - Scopus: 4In situ observations of the permanent structural modifications, phase transformations and band gap narrowing upon heating of Cu2Se/Yb/Cu2Se films(Elsevier Science Sa, 2019) Qasrawi, A. F.; Omareya, Olfat A.In this study, we have investigated the temperature dependent structural, optical and dielectric properties of Cu2Se thin films that are nanosandwiched with 50 nm thick ytterbium slab (CYC). The X-ray diffraction monitoring of the films during the heating process in the temperature range of 293-473 K has shown that the CYC films which contain both of the cubic and orthorhombic phases in its structure exhibits lattice expansion that increases the grain size and decreases the defect density, stacking faults and microstrain by 12.5% and by 28.9%, 12.8% and 11.3%, respectively. The CYC films show enhanced permanent crystallinity presented by high degree of orientation with reduction of the weight of the orthorhombic phase after cooling. On the other hand, a red shift in the energy band gap value is observed during the heating process. The analysis of the temperature dependent optical properties has shown a good correlation between the lattice expansion and energy band gap narrowing. In additions, the CYC samples are observed to exhibit negative capacitance effect that nominates the material for use in electronic circuits. The negativity of the capacitance decreased with increasing temperature due to the reduction in the defect density. (C) 2019 Elsevier B.V. All rights reserved.Article Citation - WoS: 3Citation - Scopus: 3Enhancement of the Performance of the Cu2se Band Filters Via Yb Nanosandwiching(Wiley, 2019) Khusayfan, Najla M.; Qasrawı, Atef Fayez Hasan; Qasrawi, A. F.; Khanfar, Hazem K.; Qasrawı, Atef Fayez Hasan; Department of Electrical & Electronics Engineering; Department of Electrical & Electronics EngineeringIn this article, we report the experimental and theoretical modeling on the band pass filters that are made of two thin film layers of Cu2Se coated onto aluminum substrates and nanosandwiched with 50 nm ytterbium layers. The nanosandwiching of Yb between two layers of Cu2Se is found to decrease the lattice constant, the defect density, and the strain and increase the grain size in the Cu2Se. Electrically, it is observed that, Al/Cu2Se/Al structure exhibits wave trap characteristics with notch frequency of 1.31 GHz. The Yb-layers improved the performance of the band pass filters by increasing the amplitude of the reflection coefficients, increasing the return loss values and decreasing the voltage standing wave ratios. The calculated conduction and wave trapping parameters nominate the Yb-nanosandwiched Cu2Se films for use in communication technology as they exhibit negative capacitance effect and narrow band pass range.
