A surface-plasmon-resonance (SPR)-induced absorption band has been found for low-energy Ti+ implanted (subplanted) into single-crystalline SiO2 at specific substrate temperatures. The observed SPR absorption band is in the 650–850 nm wavelength range, i.e., in the visible (red) and near-infrared regions, indicating the formation of Ti nanoparticles in the subsurface layer of the SiO2 matrix. This was confirmed by calculations based on the Mie scattering theory. The SPR absorption band becomes distinguishable only at temperatures ⩾600 °C and reached its maximum at 800 °C (1/2Tm of elemental Ti). The intensity is significantly reduced at a temperature of 1000 °C (2/3Tm). The evolution of the SPR absorption with substrate temperature is discussed.
We report the linear optical properties of a titanium nanoparticle composite formed by implantation of low energy Ti+ into single crystalline SiO2. A surface plasmon resonance (SPR) induced absorption band is found in the 650–850 nm wavelength range, i.e., in the visible (red) and near infrared regions, indicating the formation of Ti nanoparticles in the subsurface layer of the SiO2 matrix. The average size of the particles is ∼2.6 nm and the volume fraction is as low as 0.016. At the implantation energy of 9 keV and total dose of 3×1016 ions/cm2, the SPR absorption band becomes distinguishable only at temperatures greater than 600 °C and reaches its maximum at ∼800 °C (1/2Tm). Enhanced nucleation with nearly constant particle size with increasing temperature contributes to the increased SPR absorption intensity at temperatures ⩽800 °C. The SPR absorption intensity decreases significantly near 1000 °C (2/3Tm). A blueshift of the SPR absorption maximum with substrate temperature is also observed. The shape of the SPR absorption band and the difference between low and high energy implantations is discussed.
The linear optical absorption properties of a titanium nanoparticle composite formed by implantation of low energy Ti ϩ into single crystal SiO 2 are reported. Evolution of a surface plasmon resonance ͑SPR͒ induced by the formation of a metal nanoparticle composite is studied as a function of ion dose. At an implantation temperature of 25°C, the threshold dose for the appearance of the SPR is ϳ3.5ϫ10 16 ions/cm 2 , indicating that spontaneous nucleation and clustering of titanium nanoparticles in SiO 2 occurs at ϳ3.2ϫ10 22 ions/cm 3 peak concentration of implants. The average particle size and volume fraction are dependent on the ion dose. The correlation of the optical response, i.e., the intensity and frequency of the observed SPR, with the nucleation/clustering of the metal nanoparticles is discussed on the basis of Mie scattering theory and Maxwell Garnett theory.
Surface-plasmon-resonance-induced absorption of a metal-oxide nanoparticle compositeThe annealing effects on the surface plasmon resonance induced absorption band of a Ti-SiO 2 nanoparticle composite have been reported. Low energy ion implantation followed by thermal annealing is found to improve the surface plasmon resonance ͑SPR͒ absorption of Ti nanoparticles, a result that is different from substrate heating during implantation. The SPR absorption becomes distinguishable when the temperature is greater than 200°C and reaches its maximum at ϳ600°C. The intensity decreases significantly at higher temperatures due to high temperature enhanced diffusion which lowers the local Ti concentration and the possible formation of titanium oxides and silicides. A blueshift of the SPR absorption induced by annealing is also observed.
Under ultrahigh vacuum conditions, extremely small Ge nanodots embedded in SiO2, i.e., Ge–SiO2 quantum dot composites, have been formed by ion implantation of Ge+74 isotope into (0001) Z-cut quartz at a low kinetic energy of 9keV using varying implantation temperatures. Transmission electron microscopy (TEM) images and micro-Raman scattering show that amorphous Ge nanodots are formed at all temperatures. The formation of amorphous Ge nanodots is different from reported crystalline Ge nanodot formation by high energy ion implantation followed by a necessary high temperature annealing process. At room temperature, a confined spatial distribution of the amorphous Ge nanodots can be obtained. Ge inward diffusion was found to be significantly enhanced by a synergetic effect of high implantation temperature and preferential sputtering of surface oxygen, which induced a much wider and deeper Ge nanodot distribution at elevated implantation temperature. The bimodal size distribution that is often observed in high energy implantation was not observed in the present study. Cross-sectional TEM observation and the depth profile of Ge atoms in SiO2 obtained from x-ray photoelectron spectra revealed a critical Ge concentration for observable amorphous nanodot formation. The mechanism of formation of amorphous Ge nanodots and the change in spatial distribution with implantation temperature are discussed.
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