Spectra of surface-enhanced Raman scattering of nanocluster NaXe

Abstract

The integrated ultraviolet (UV)-micro-laser-matrix can be expected, if the novel nanomaterial with a matrix distribution can emit UV radiation and easily inverses the population between its ground and excited states. Solid NaXe nanoclusters should belong to such a nanomaterial. Metallic Na colloids of nanometer size have been formed as the results of the aggregations of F centers in heavily irradiated NaCl [1]. It has been indicated by the measurements of transmission electron microscopy (TEM) that alkali atoms, including Na and K, in alkali metal colloids retain their original face centered cubic (fcc) positions within the alkali halide matrix and that their lattice parameters are not far different from their host matrix [2]. It has been also evidenced by TEM and selected-area electron diffraction experiments that noblegas ions implanted into metals and magnesium oxide can be trapped and solid noble-gas inclusion can be formed [3]. Their positions have been found to be fccs in fcc matrix [3]. It has been also demonstrated by our former experiments [4, 5] that the novel solid NaXe can be prepared under the appropriate conditions of xenon ion implantation into NaCl samples and a strong 355 nmUV-radiation emission can be observed. In this paper, the surface-enhanced Raman scattering (SERS) spectra of nanocluster NaXe in NaCl are measured at room temperature and their characteristics are discussed. In the experiment, pure NaCl powder, in which the grain diameters are smaller than 53 µm, is pressed to disks as samples. Xenon ions are implanted at 10 −6 Torr by using an accelerating voltage of 200 kV. The xenon ion flux is 5×10 17 ions/cm 2 . Under this implantation condition, solid NaXe nanoclusters with blue color are formed through the interaction between solid Xe and metallic Na colloids in xenon-ion–implanted NaCl samples. The sizes of solid NaXe nanoclusters are measured to be within 80 nm by scanning electron microscopy (Hitachi S-3500N). The Raman-scattering is often enhanced by the colloids formed on the surface of the sample. This process is called SERS [6]. These SERS spectra can provide information about the nature and geometry of the colloids in samples. Therefore, low-frequency Raman-scattering spectra are used to study the colloidal structure in our ∗ Author to whom all correspondence should be addressed.