Optical and TEM characterization of phase transformation in Zn ion implanted and thermal oxidized quartz

Abstract

Metal and metal oxide nanoparticles (NPs) embedded in various matrices have been the object of increasing interest due to their peculiar physical properties significantly different from the corresponding ones of bulk material. Metallic Zn NPs can be used in UV photo-detectors. Zinc oxide NPs play an important role too, since ZnO has direct band gap of 3.37eV, large exiton binding energy of 60meV, sorption effect, room temperature ferromagnetism and others. So they can be used in varies perspective electron devices. In this paper the optical parameters and transmission electron microscopy (TEM) characterization of Zn implanted quartz during NP formation at annealing are reported.

Optical-grade high-pure (OH^-: 50ppb) amorphous quartz slides were implanted by ⁶⁴Zn⁺ ions with fluence of 5×10¹⁶/cm² and energy of 50keV. To avoid the magnificent substrate heating during implantation the ion current density was less than 0.5μA/cm². Than the samples were subjected to isochronally during 1h oxidation in temperature ranges from 400 up to 800^oC. The Zn contained phase creation and its thermal evolution were investigated by recording the optical transmittance spectra at room temperature in a spectral range of 200-800nm and by photoluminescence at temperatures of 10-300K in a spectral range of 350-800nm using an illumination of He-Cd laser with wavelength of 325nm. Visualization and identification of NPs was made by study of the cross section samples TEM fitted with electron diffraction, an EDAX detector attachment for X-ray energy dispersive spectroscopy (EDS), and with a high angle annular dark field detector (HAADF) for scanning operation. The EDS maps of the element distribution and the NP sizes were determined in the scanning TEM regime.

As a result of these studies it was found that after the quartz implantation by ⁶⁴Zn⁺ ions with fluence of 5×10¹⁶/cm² and energy of 50keV the amorphous metallic Zn NPs with an average radius of 3 nm were created. During process of sequentially isochronally furnace annealing in oxygen atmosphere in 1h in temperature ranges from 400 up to 800^oC in samples there was phase transformation from metallic Zn phase to its oxide form. After annealing at 800^oC the Zn NPs transform to the ZnO or/and Zn₂SiO₄ phase with average radius of 4,5nm.