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Low-temperature deposition of ZnO thin films by DC reactive sputtering at high oxygen partial pressure
|Mohamed Kechouane 1, Abderrahmane Boughelout 1, Abdel Yazid Kheireddine 2, Kamel Taibi 3, Hamid Menari 4, Menouar Siad 5, Amar Manseri 4
1. Laboratoire "Couches Minces et Semiconducteurs" - USTHB - Faculté de Physique -, BP 32 El-Alia - Bab-Ezzouar, Alger 16111, Algeria
Transparent conducting zinc oxide (ZnO) has received a vast amount of attention in the last few years. This material is both transparent and conductive with a wide variety of applications (solar cells, microelectronics, sensors). ZnO can be deposited by a variety of techniques such as radio frequency sputtering and direct current magnetron sputtering, pulsed laser deposition and molecular beam epitaxy. The material properties (structural, optical and electrical properties) of the ZnO thin film are critically related to the specific growth technique employed and to the growth parameters used.
Zinc oxide (ZnO) films were grown on corning glass and crystalline silicon substrates at room temperature and 100°C using DC reactive sputtering with an argon/oxygen mixture at constant working total pressure of 100 Pa. The ZnO thin films were investigated by optical transmission, X-ray diffraction (XRD), scanning electron microscopy (SEM), Rutherford backscattering spectrometry (RBS) and electrical conductivity measurements. The transmission measurements have shown that all films exhibit high transmittance in the 400–2500 nm range. The optical transmission is in an increasing order of oxygen content in the as-grown films. The crystalline structure of ZnO thin films indexed by XRD reveals hexagonal ZnO phase with cell parameters a=3.2499 Å and c=5.2066 Å. The XRD spectra consisted of a ZnO phase oriented with its c-axis with a strong (002) peak, indicating that the films are highly texturized along the c-axis perpendicular to the substrate surface. No diffraction from randomly oriented grains or impurity phases can be observed from the X-ray patterns related to the as-grown and annealed samples. The thermal annealing at 300°C have the effects of narrowing the diffraction peak, indicating that grain growth has occurred, and shifting the (002) peaks to higher 2q angles.V From the scanning electron microscopy images, significant changes are observed according to the oxygen partial pressure used during the film deposition. The elementary chemical analysis (EDX) reveals the presence of 66Zn and 16O in the ZnO layer. A very large increase in electrical conductivity, up to nine orders of magnitude, was observed in as-grown ZnO films upon vacuum-annealing at 300°C for one hour, reaching as high as 0.2 W-1.cm-1.
Presentation: Poster at E-MRS Fall Meeting 2009, Symposium C, by Mohamed Kechouane
See On-line Journal of E-MRS Fall Meeting 2009
Submitted: 2009-05-05 09:57 Revised: 2009-06-07 00:48