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Article Citation - WoS: 6Citation - Scopus: 6Characterization of the A1/Ge/In2Se3/Ga2S3/Al hybrid tunneling barriers designed for Gigahertz/Terahertz applications(Elsevier Science Sa, 2018) Qasrawi, A. F.; Omareya, Olfat A.In the current work, we report the design and performance of a tunneling amorphous thin film hybrid device made of Ge/In2Se3/Ga2S3 sandwiched between two aluminum thin films. Each of the stacked semiconducting layers are of 200 nm thicknesses. The hybrid device which is composed of a p-n junction between two Schottky shoulders is designed to have two valence band offsets of 0.59 and 0.84 eV at the Ge/In2Se3 and at In2Se3/Ga2S3 interfaces, respectively The offsets which caused two quantum confinements forces the device to exhibit field effect assisted thermionic and thermionic transport mechanisms under the reverse and forward biasing conditions, respectively. When an alternating current signal is imposed between the terminals of the device, the device conducted by the quantum mechanical tunneling of charge carriers and by the correlated barrier hopping above and below 0.180 GHz, respectively. The hybrid structure are also observed to exhibit series and parallel resonance at the switching frequency between the two conduction mechanisms. It also exhibited negative differential capacitance effect in the frequency domain of 0.18-1.80 GHz. For the Al/Ge/In(2)Se3/Ga2S3/Al hybrid structure the microwave cutoff frequency reached 100 GHz. The latter value is promising as it indicates the ability of using the device as fast switches and microwave/Tera wave traps.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.
