Cathodoluminescence property of ZnO nano-phosphors fabricated by pulsed Nd:YAG laser ablation in plasma circumstance

Cathodoluminescence (CL) with energy-controlled electron beams was used to study the inner structure of ZnO nano-phosphors fabricated by YAG laser ablation under oxygen gas and oxygen plasma circumstances. Varying accelerating voltages of electron beams from 1.0 to 3.0 kV, it was clearly seen that the CL spectrum in the case of ZnO nano-phosphors fabricated under the oxygen gas background changed from a broad one centered at approximately 500 nm to a narrow one peaked at 380∼400 nm. This result indicates that there is an oxygen vacancy-rich shell in the surface area and a fine crystalline ZnO structure in the inner core region. Under the oxygen plasma circumstance at 500 Pa, however, we found that there is a crystalline structure in the surface layer of ZnO nano-phosphors due to the sufficient supply of oxygen ions and atoms and suppression of the formation of oxygen vacancy.     

Resistive switching behavior of (Zn1−xMgx)O films prepared by sol-gel processes

Highly c-axis oriented sol-gel (Zn_1 − xMg_x)O films were deposited on Pt/Ti/SiO2/Si substrates. Resistive switching behaviors with stable switching and high resistance ratio were demonstrated for the Pt/(Zn_0.9Mg_0.1)O/Pt stacks. The effect of the film thickness and the annealing temperature on resistive switching was discussed. Higher substitution of Mg for Zn results in higher resistance of (Zn_1 − xMg_x)O films, which is beneficial for resistive switching to occur at thinner film thickness. The mechanisms dominating the low and the high resistance states are Ohmic conduction and Poole-Frenkel emission, respectively. The resistance ratio varies from 140 to 1000, which is much higher than the value 25 reported recently for sol-gel (Zn_0.8Mg_0.2)O films. Films annealed at higher annealing temperatures possess higher resistance ratio.     

Hysteresis loops of polarization and magnetization in (BiNd0.05)(Fe0.97Mn0.03)O3/Pt/CoFe2O4 layered epitaxial thin film grown by pulsed laser deposition

(BiNd_0.05)(Fe_0.97Mn_0.03)O₃ (BNFM)/Pt/CoFe₂O₄ (CFO) layered thin film was fabricated on (100) SrTiO₃ substrate by pulsed laser deposition. BNFM, Pt, and CFO layers were epitaxially grown on the substrate. Almost no increase of leakage current due to the formation of heteroepitaxial structure was found, and well-saturated hysteresis loops in the polarization vs electric field and magnetization vs magnetic field curves coexist at room temperature. The remnant polarization and remnant magnetization values were 55 μC/cm², and 70-145 mA/m, respectively.     

The incorporation of preformed metal nanoparticles in zinc oxide thin films using aerosol assisted chemical vapour deposition

The feasibility of Aerosol Assisted Chemical Vapour Deposition (AA-CVD) has been investigated for the growth of zinc oxide (ZnO) films containing preformed metal nanoparticles. The deposition parameters were first established for ZnO thin films, by varying the heating configuration, substrate temperature and deposition time. Films were characterised using Scanning Electron Microscopy and X-Ray Diffraction. As-deposited films, grown at 250 °C, were mostly amorphous and transformed to highly crystalline Wurtzite ZnO at higher substrate temperatures (400-450 °C). A change in the preferential orientation of the films was observed upon changing (i), the substrate temperature or (ii), the heating configuration. Following this, the applicability of the AA-CVD process for the incorporation of preformed nanoparticles (platinum and gold) in ZnO thin films was investigated. It was found that surface agglomeration occurred, such that the ZnO films were capped with an inhomogeneous coverage of the metal. These layers were characterised using Transmission Electron Microscopy and Electron Diffraction. A possible mechanism for the formation of these metal surface clusters is presented.