Ion Beam Synthesis and Optical Properties of Zn and Zno Nanocrystals in Sio 2 and Caf 2 Substrates
- PDF / 250,273 Bytes
- 7 Pages / 612 x 792 pts (letter) Page_size
- 3 Downloads / 217 Views
T7.8.1
ION BEAM SYNTHESIS AND OPTICAL PROPERTIES OF Zn AND ZnO NANOCRYSTALS IN SiO2 AND CaF2 SUBSTRATES Y.C. Liu,1,2 R. Mu3,*, H.Y. Xu,2 Y.M. Lu,2 D.Z. Shen,2 X.W.Fan2, D. O. Henderson3 and C.W. White4 1 Advanced Center for Optoelectronic Functional Materials Research, Northeast Normal University, Changchun 130024, PRC. 2 Key Laboratory of Excited State Processes, CIOFMP-CAS, Changchun, China. 3 Center for Photonic Materials and Devices, Fisk University, Nashville TN, USA 4 Condensed Matter Sciences Division, Oak Ridge National Laboratory, Oak Ridge, TN USA
ABSTRACT Ion implantation was used to inject zinc ions into crystalline CaF2 and amorphous SiO2 substrates. Zn or ZnO nanoparticles were formed after annealing in a reducing (4% H2 + 96% Ar) or an oxidizing (10%O2 + 90% Ar ) atmosphere, respectively. When the sample was annealed in a reducing atmosphere, the absorption band at ~ 5.3 eV for zinc implanted into SiO2 was attributed to zinc metal colloids. The absorption peak observed in the 4.3 – 4.7 eV region was due to the formation of ZnO nanocrystals, after the sample was annealed in an oxidizing environment. Both X-ray diffraction (XRD) and X-ray photospectroscopy (XPS) were used to confirm ZnO nanocrystal formation. For zinc implanted into CaF2, the as-formed ZnO nanocrystals were aligned with their [002] axes parallel to the [111] axis of the CaF2. Photoluminescence (PL) spectra showed UV and green emission from the zinc-implanted silica samples annealed under an oxygen atmosphere; however, no green emission was observed for ZnO formed in a CaF2 substrate. An additional emission was observed at ~ 420 nm which might be due to F centers in CaF2 created by ion beam damage. INTRODUCTION The study of the physical and optical properties of nanophase materials assembled in various solid hosts could eventually lead to important advances in electronics and optics. However, the present understanding of nanophase materials, such as metal colloids and quantum dots (QDs), is far from complete due to the complexity of structural, physical and optical properties of nanoparticles, and the many interactions between the nanoparticles and the host material in which they are embedded. Depending upon the physical properties of the confining host and the confined guest materials (i.e., nanoparticles), many unique mechanical, thermal and optical properties have been observed and related to different types of confinement effects. For example, 1) the physical confinement, the interfacial interaction between guest and host, and the reduction of the physical size of the confined particles can lead to a) hardness change of materials;[1] b) depression of the melting and freezing phase transition temperatures;[2] and c) alteration of crystal nucleation and growth characteristics;[3] 2) the quantum confinement of free electrons in metals and excitons in semiconductors can result in the observation of the surface plasmon resonance (SPR) and the shifts of optical band gap, respectively;[4,5] 3) dielectric confinement gives rise to surface
Data Loading...
