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UNIVERSITY OF BUCHAREST
FACULTY OF PHYSICS Guest
2024-11-22 2:36 |
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Conference: Bucharest University Faculty of Physics 2011 Meeting
Section: Solid State Physics and Materials Science
Title:
Double layer structure of ZnO thin films deposited by RF-magnetron sputtering
Authors:
C. Besleaga(1), G.E. Stan(2), A.C. Galca(2), L. Ion(1), S. Antohe(1)
Affiliation:
1 University of Bucharest, Faculty of Physics, P.O. Box MG-11, 077125 Bucharest-Magurele, Romania
2 National Institute of Materials Physics, P.O. Box MG-7, 077125 Bucharest-Magurele, Romania
E-mail
cristina@solid.fizica.unibuc.ro
Keywords:
ZnO thin films; magnetron sputtering; interface; VRH mechanism; XRR
Abstract:
Transparent ZnO films are synthesized by RF-magnetron sputtering (1.78 MHz) onto glass substrates, using a mild-pressed ZnO powder target. The depositions were carried out at three inert argon pressures (0.25 Pa, 0.30 Pa, 0.45 Pa) and at two substrate temperatures (100°C, 400°C), respectively. The role of the sputtering conditions on ZnO thin films nanostructuring, optical properties and morphology is investigated by X-ray diffraction (XRD), X-ray reflectometry (XRR), Spectroscopic ellipsometry (SE) and Atomic Force Microscopy (AFM). The XRD analyses reveal that ZnO films are highly oriented on the [00l] direction, having nanosized crystallites. Right-angle asymmetry of the (002) diffraction peak is observed. The peak profile analysis using Pseudo-Voight functions unveil a double overlapped peak structure with different coherent zone size values. A double layer structure is evidenced by analyzing the XRR data. Samples prepared at 0.3 Pa at a temperature of 400°C have a 3 nm bottom layer consisting of highly depleted in oxygen ZnO1-x structure, continued by a 53 nm top layer of textured ZnO. Electrical measurements show that temperature dependence on the conductivity is well described by the Mott variable range hopping (VRH) law. The samples obtained at 400°C have a significantly lower resistivity.
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