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Title: | Design and Characterization of Se/WO3 Thin Film Transistors رسالة ماجستير |
Authors: | Daragme, Rana Bassam$AAUP$Palestinian |
Keywords: | x-ray,optical analysis,spectrospy analysis |
Issue Date: | 2020 |
Publisher: | AAUP |
Abstract: | In this thesis, we have considered the physical design and physical characterization of Se/WO3 heterojunctions. The Se/WO3 heterojunction devices are prepared by the thermal evaporation technique under vacuum pressure of 10-5 mbar onto glass and Yb thin film substrates. The X-ray diffraction analysis on the Se, WO3 and Se/WO3 thin films have shown that, the selenium films which are coated onto glass substrate exhibit a time dependent phase transition from amorphous to polycrystalline monoclinic cells within a period of two weeks. On the other hand, when these freshly prepared Se films were immediately coated with WO3, the amorphous nature of structure disappears and polycrystalline phase dominates. Immediate phase transitions from amorphous to polycrystalline was also achieved via replacement of glass by cubic Yb substrates. Optically, the Se/WO3 interfaces exhibit conduction and valence band offsets of values of 1.58 and 0.73 eV, respectively. The interfacial of WO3 with Se is also observed to increase the light absorbability of selenium by more than 5-times. On the other hand, the real part of the dielectric constant of Se/WO3 exhibited various resonance peaks in the studied range of spectrum. The pronounced dielectric response is observed in the IR range of spectrum. vii Theoretically with construction of the energy band diagram for a device structure formed of Yb/Se/WO3/Yb. It was observed that the device under study exhibit complex band diagram presented by two back to back Schottky shoulders at the Yb/Se and Yb/WO3 interfaces. The large lattice mismatch and differences in the conduction and valence band offsets also formed a depletion region at the Se/WO3 interface which behaves like a pn junction. Experimental verification of these designs were actualize by the capacitance voltage characteristics which revealed features of field effect transistors. As practical application for the proposed Yb/Se/WO3/Yb devices, the impedance spectroscopy were measured in the frequency domain of 0.01-1.8 GHz. The Ac signal analysis has shown that these kinds of devices can be employed as band stop filters with notch frequency of 0.74 GHz. The device reject all signals above the notch frequency and pass signals of lower frequency. |
Description: | Master’s degree in Physics |
URI: | http://repository.aaup.edu/jspui/handle/123456789/2632 |
Appears in Collections: | Master Theses and Ph.D. Dissertations |
Files in This Item:
File | Description | Size | Format | |
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رنا ضراغمة.pdf | 2.48 MB | Adobe PDF | View/Open |
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