Study of optical properties and TEM of Nanoparticles in Ni + -implanted Sapphire
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Study of optical properties and TEM of Nanoparticles in Ni+-implanted Sapphire X. Xiang1, X.T. Zu1,∗, S. Zhu2, L.M. Wang2 1 Department of Applied Physics, University of Electronic and Technology of China, Chengdu, P. R. China, 610054, 2 Department of Nuclear Engineering and Radiological Sciences, University of Michigan, Ann Arbor, MI48109, USA ABSTRACT 64-keV Ni ion implantation was performed at room temperature up to a dose of 1×1017 cm-2 in α-Al2O3 single crystals. The charge states, structure and optical properties of metallic embedded Ni nanoparticles were studied by using X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM) and optical spectroscopy, respectively. XPS analysis showed that implanted Ni ions are mainly in charge state of metallic Ni0. Nanoparticles distributed from the surface to 30 nm below the surface were observed in a bright-field cross-sectional image. The size of nanoparticles ranges from 1 to 5 nm in diameter. A selected area electron diffraction (SAED) pattern shows Ni nanoparticles with lattice parameter a = 0.352 nm. A high-resolution electron microscopy (HREM) image indicated the Ni-implanted area had been entirely amorphized. A new broad absorption band centered at 400 nm appeared in the optical absorption spectrum of the as-implanted crystal, due to surface plasma resonance (SPR) of Ni nanoparticles.
INTRODUCTION Ion implantation has become a versatile and powerful technique for forming nanoparticles. It shows promise as a means of modifying the near-surface mechanical, electrical, optical and magnetic properties in insulator matrices, due to quantum confinement effects [1,2]. Ion implantation has been used to produce metallic nanoclusters embedded in the near-surface region of a ceramic matrix for three decades [3]. Many studies have concentrated on optical properties of silica glass, and metallic nanocrystals formed by ion implantation, including Au, Ag, Ga, Cr, Fe and other transition metals [4-10]. Some metallic nanocrystals, such as Au, Al, Fe, Y, Ag, Cu, formed by ion implantation have been studied in Al2O3 host crystals [11-16]. To our knowledge, there are no reports on metallic Ni nanoparticles formation induced by ion implantation in Al2O3 single crystals. In this paper, the charge states, structure and optical properties of metallic Ni nanoparticles in Ni-implanted Al2O3 crystals were studied by using X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), and optical spectroscopy.
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Corresponding author. E-mail: [email protected], Tel & Fax: 86 28 83201939.
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EXPERIMENTAL DETAILS The materials used in this study were colorless, transparent synthetic single crystals of αAl2O3. The wafers were cut perpendicularly to the axis, 10×15×1 mm3 in size. The samples were optically polished to a mirror-like finish before ion implantation. The Ni ion implantation in Al2O3 was performed at an energy of 64 keV with dose of 1×1017 cm-2 in a vacuum chamber of 1.8×10-3 Pa. The samples were kept at room temperature with the cir
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