6 results
Search Results
Now showing 1 - 6 of 6
Article Citation - WoS: 6Citation - Scopus: 6Gold and Ytterbium Interfacing Effects on the Properties of the Cdse/Yb Nanosandwiched Structures(Elsevier Science Bv, 2018) Alharbi, S. R.; Qasrawi, A. F.Owing to the performance of the CdSe as an optoelectronic material used for the production of quantum dots, photosensors and wave traps we here, in this article, report the enhancements in structural and electrical properties that arises from the nanosandwiching of a 40 nm thick Yb film between two films of CdSe (CYbC-40). The CdSe films which were deposited onto glass, Yb and Au substrates are characterized by X-ray diffraction, temperature dependent electrical conductivity and impedance spectroscopy measurements in the frequency range of 10-1800 MHz. The analysis of the XRD patterns have shown that the glass/CdSe/Yb/CdSe films exhibit larger grain size and lower strain, defect density and lower stacking faults compared to the not sandwiched CdSe. In addition, it was observed that the Yb shifts the donor states of the n-type CdSe from 0.44 to 0.29 eV leading to a modification in the built in voltage of the material. On the other hand, the design of the energy band diagram has shown the ability of the formation of the Au/CYbC-40/Yb as Schottky (SB) and the Au/CYbC-40/Au as back to back Schottky barriers (BBSB). While the SB device show low band pass filter characteristics, the BBSB device performed as band stop filters. The BBSB device exhibited negative capacitance effects with filtering features that reveal a return loss of 42 dB at similar to 1440 MHz.Article Citation - WoS: 2Citation - Scopus: 2Dielectric and Optoelectronic Properties of Inse/Cds Heterojunctions(Springer, 2018) Abusaa, M.; Qasrawi, A. F.; Shehada, Sufyan R.The effect of an InSe substrate on the structural, optical and dielectric properties of CdS/CdSe heterojunctions prepared by physical vapor deposition technique under vacuum pressure of 10(-8) bar are reported. The structural analysis carried out by x-ray diffraction revealed a strained type of growth of the CdS/CdSe heterojunction onto the InSe along the axis of the hexagonal lattice. The lattice mismatches and strained nature of the heterojunctions associated with the InSe participation causes a quantum confinement that results in a red shift in the energy band gap, enhanced near infrared (IR) light absorbability, and valence band offsets of 0.62eV and 0.53eV for the InSe/CdS and CdS/CdSe interfaces, respectively. In addition, a pronounced enhancement in the real part of the dielectric constant by 2.5 times is observed at 1.25eV. Furthermore, the Durde-Lorentz modeling of the optical conductivity of the CdS/CdSe and InSe/CdS/CdSe reveals significant increases in the drift mobility values from 43.8cm(2)/Vs at the CdS/CdSe interface to 100.0cm(2/)Vs upon replacement of glass by an amorphous InSe substrate. The other optical conduction parameters including the free carrier scattering time at the femtosecond level, the plasmon frequency and the free carrier density are also improved accordingly. The photocurrent illumination intensity dependence for the studied system showed that the presence of InSe increases the photocurrent values and changes the recombination mechanism from sublinear at the surface to trap-assisted recombination. The smart feature of the InSe/CdS/CdSe system is that the structurally controlled quantum confinement results in having mobile photocarriers arising from the enhanced absorbability and large dielectric response in the IR region.Article Citation - WoS: 8Citation - Scopus: 10Temperature Effects on Optical Characteristics of Cdse Thin Films(Elsevier Sci Ltd, 2021) Gullu, H. H.; Isik, M.; Surucu, O.; Gasanly, N. M.; Parlak, M.CdSe is one of the significant members of II-VI type semiconducting family and it has a wide range of technological applications in which optoelectronic devices take a special position. The present paper reports the structural and optical characteristics of thermally evaporated CdSe thin films. XRD pattern exhibited preferential orientation along (111) plane while atomic composition analyses resulted in the ratio of Cd/Se as closer to 1.0. Temperature-dependent band gap characteristics of CdSe thin films were investigated for the first time by carrying out transmission experiments in the 10-300 K range. The analyses showed that direct band gap energy of the compound decreases from 1.750 (at 10 K) to 1.705 eV (at 300 K). Varshni model was successfully applied to the temperature-band gap energy dependency and various optical constants were determined. Raman spectrum of CdSe thin films was also presented to understand the vibrational characteristics of the compound. The present paper would provide worthwhile data to researchers especially studying on optoelectronic device applications of CdSe thin films.Article Citation - WoS: 8Citation - Scopus: 8Optical Interactions in the Inse/Cdse Interface(Wiley-v C H verlag Gmbh, 2016) Qasrawi, A. F.; Rabbaa, S.In this work, the structural and optical properties of the InSe/CdSe heterojunction are investigated by means of X-ray diffraction and ultraviolet-visible light spectrophotometry techniques. The hexagonal CdSe films that were deposited onto amorphous InSe and onto glass substrates at a vacuum pressure of 10(-5)mbar, exhibited interesting optical characteristics. Namely, the absorption, transmission, and reflection spectra that were recorded in the incident light wavelength range of 300-1100nm, for the InSe, CdSe, and InSe/CdSe interface revealed direct allowed transition energy bandgaps of 1.44, 1.85, and 1.52eV, respectively. The valence-band offset for the interface is found to be 0.36eV. On the other hand, the dielectric constant spectral analysis displayed a large increase in the real part of the dielectric constant associated with decreasing frequency below 500THz. In addition, the optical conductivity spectra that were analyzed and modeled in accordance with the Drude theory displayed a free-carrier average scattering time of 0.4fs and a drift mobility of 6.65cm(2)V(-1)s(-1) for the InSe/CdSe interface. The features of this interface nominate it as a promising member for the production of optoelectronic Schottky channels and as thin-film transistors.Article Citation - WoS: 2Citation - Scopus: 2Enhancement of Photoconductive Performance of Cdse Via Yb Nanosandwiching(Elsevier Gmbh, Urban & Fischer verlag, 2018) Qasrawi, A. F.In this work, we have explored the effects of the ytterbium nanosandwiching on the structural and optoelectronic properties of CdSe thin films. A ytterbium layer of thickness of 200 nm was sandwiched between two layers of CdSe (1.0 mu m). The structural investigations have shown that the hexagonal structure of CdSe is deformed by 1.9% and 0.8% along the a and c - axes, respectively, by the inclusion of the Yb in the structure of CdSe. In addition, a systematic redshifts in the interference patterns of the optical transmittance and reflectance were observed. Accordingly, the optical absorption coefficient spectra of CdSe which displayed two energy gap values of 1.62 and 1.36 eV, are also redshifted. On the other hand, when exposed to blue light irradiation, the steady state and time dependent photocurrent analysis revealed a remarkable enhancement presented by a three orders of magnitude increase in the responsivity of CdSe upon Yb sandwiching. The photocurrent was observed to be limited by the saturation of the surface states and traps that causes longer relaxation constant compared to that of pure CdSe. (C) 2017 Elsevier GmbH. All rights reserved.Article Citation - WoS: 3Performance of the Yb/n< Tunneling Barriers(Amer Scientific Publishers, 2018) Qasrawi, A. F.In this article, the design and performance of the CdSe which are deposited onto thin films of Yb metal is reported and discussed. The thin films of CdSe which are deposited by the physical vapor deposition technique are observed to exhibit slightly deformed hexagonal polycrystalline nature with excess amount of Cd as confirmed by the X-ray, energy dispersive X-ray spectroscopy and scanning electron microscopy techniques. The n-type CdSe is also found to form a Schottky barrier of tunneling type when sandwiched between Yb and carbon. The quantum mechanical tunneling mechanism in this device which was tested and modeled in the frequency domain of 10-150 MHz is found to exhibit average intersite separations of similar to 5 nm. The tunneling device exhibited a widening in the depletion region associated with significantly large capacitance tunability in the studied frequency domain. On the other hand, as an optoelectronic device, the Yb/n-CdSe/C Schottky diode exhibited a responsivity of similar to 0.10 NW, photosensitivity of 6.5 x 10(4) and external quantum efficiency of 54% when biased with 1.0 V and exposed to laser light of wavelength of 406 nm.
