Ni ion-implanted α-Al2 O3

1. Optical properties of metallic nanoparticles in Ni-ion-implanted α-Al2O3 single crystals X. Xiang and X. T. Zu S. Zhu and L. M. Wang Younes Sina

2. Ion implantation A powerful technique for forming nanoparticles Potential promise as a means of modifying the near surface mechanical, electrical, optical, and magnetic properties in insulator materials due to quantum confinement effects

3. α-Al2O3has been often used in microelectronic devices or as window materials Single crystal Sapphire has a highthermal conductivity, volume resistivity, hardness and wear resistance, as well as a high upper use temperature. The energy band gap is large (≈9 eV). Sapphire is a transparent material having useful transmission of wavelengths in the range 0.2 to 5.5 microns. It is much stronger than glass and can be used as viewing windows in high pressure and vacuum applications.

4. 5x1016Ni+/cm2 64 keV 1 0 mm Vacuum 1.8x10-3 Pa 15 mm <0.5 μA/Cm2 To avoid heating the sample 1 mm

5. Charge state XPS (X-ray photoelectron spectroscopy) Structure of metallic Ni nanoparticles in Ni- implanted Al2O3 crystals TEM ( Transmission electron microscopy) Optical properties Optical spectroscopy

6. XRP (X-ray photoelectron spectroscopy) at room temperature with KRATOS X SAM 800 with monochromatic Al Kα(hν =1486 eV) Ar+ ion beam etching of sample at energy of 3 keV and current density of 10 μA/Cm2 Etching rate = 1 nm/min 2 nm etched Ni-implanted samples with Ar+ in order to remove surface contamination

7. Etching depth 2 nm Etching depth 12 nm X-ray photoelectron spectra of Ni 2p3/2 energy level of Ni+-implanted Al2O3 crystals showing implanted Ni ions mainly in charge state of metallic Ni0. The charge states of Ni have no distinct change with the increasing etching depth. Real line-experimental curve, point line Gaussian simulated curve.

8. Ni2+(NiAl2O4) Ni3+ (Ni2O3) Ni2+(NiAl2O4) Ni3+ (Ni2O3) Ni0 Ni0 852.3 852.3 856.6 856.6 Etching depth 2 nm Etching depth 12 nm Ni concentration= 9.55% Ni concentration= 9.84% The charge states of Ni have no distinct change with the increasing etching depth.

9. JEOL 2010 F (STEM & TEM) at 200 keV bright-field HAADF ( high angle annular dark-field) Probe size 0.2 nm Collection angle of 50 mrad HREM ( high-resolution electron microscopy)

10. bright-field HAADF STEM Φ = 1 – 5 nm Al2O3 A bright-field (a) and a HAADF STEM (b) cross-sectional image in the near surface of as-implanted Al2O3 matrix. Nearly spherical embedded nano-particles, 1–5 nm in diameter, are distributed from the surface to 30 nm below the surface.

11. HREM Ni-ion implanted area is amorphized entirely A HREM image showing structure of Ni nanoparticles in the near surface of Al2O3 matrix

12. Optical Spectroscopy With SHIMATZU UV-2100 spectrophotometer Wavelength from 200-800 nm Luminescencetest With HITACHI 850 photoluminescence spectrophotometer Xe lamp excitation source

13. No detection of emission band in the as-implanted sample under a Xe lamp excitation wavelength of 250-430 nm F+color center form by O2- vacancy captured single e Surface Plasmon resonance F color center: F++e-> F Broadband peaked at 400 nm due to SPR of Ni0 Crystal turning gray as-implanted electron-irradiated as-grown 225 nm 250 nm 400 nm Optical absorption spectra of as-grown, as-implanted and electron irradiated Al2O3crystals. A broadband peaked at 400 nm appeared in the Ni-implanted sample. (1)as-grown (2) electron-irradiated, and (3) as-implanted

14. Single crystal of α-Al2O3 (rhombohedral) has a wide band gap (Eg≈9 eV). Therefore, its intrinsic absorption is in the ultraviolet wave band. Pure single crystals of α-Al2O3 look colorless and transparent in the visible region. Then from 380-740 nm (visible wave band) its absorption spectrum is a smooth line. intrinsic absorption

16. Room temperature implantation at dosage above the threshold dose for spontaneous nanocrystals formation

18. Ion species

19. Target temperature

20. Orientation of the ion beam relative to crystallographic axesExamples: Disorder increases faster with increasing dose for the c-axis orientation than the a-axis orientation. (0001) Surface implanted sapphire with Fe ion become amorphous at a dose between 1x1017 and 2x1017

21. Metallic nanocrystals has a small size and high specific surface area. Optical properties of metallic nanoparticles embedded in a dielectric host are dominated by Surface Plasmon Resonance (SPR). For the smaller particle size, the plasmon band are relatively weak, broadened, and is shifted to higher energy due to quantum confinement. Based on Xu and Käll model using Mie theory, SPR peak shift towards low energy (higher wavelength) with increasing refractive index of surrounding medium.

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