Er, Tm Doped ZnO / Al ₂ O ₃ Photoluminescence

(1) Research on the broadband emission from Er Tm and Si codoped ZnO filmIn order to achieve broadband emission from ZnO, the semiconductor material, we have discovered the influence by Si-NCs as a sensitizer to the broadband emission from Er and Tm. The bilayer film Er:Si:ZnO(40nm)/Tm:Si:ZnO(40nm) and Er: ZnO(40nm)/Tm:ZnO(40nm) are made. Broadband emission are obtained after the two films are annealed at900℃. However, the emission from former is enhanced by an order of magnitude. We discovered the bilayer film turns into the monolayer film (Er:Tm:Si:ZnO) with the Er3+and Tm3+diffusing completely and silicon nanacrystals (Si-NCs) have been formed from the concentration depth profiles of different elements measured by XPS and the TEM. The PL spectra of the annealed film Er:Tm:Si:ZnO(80nm) have been measured and the energy transfer processes among Er, Tm and Si-NCs have been discussed.(2) The mechanism of enhancement of emission from Er by Si-NCsAlternately Er and Si codoped Al2O3multilayer film:{[Er:Al2O3(6nm)/Al2O3(2nm)/Si:Al2O3(4nm)]×10} and Er doped Al2O3monolayer film:[Er:Al2O3(60nm)]have been synthesized by co-sputtering. The photoluminescence (PL) from the multilayer film is enhanced by20times than that from monolayer one when they are excited by the488nm and795nm laser which both can be absorbed by Er. When they are excited by the476nm laser, there is nearly no emission from both films. It indicates that the emission enhancement can not be due to the energy transfer from Si-NCs to Er ions but the reduction of nonradiative decay of Er ions. So it may be concluded that Si-NCs can not only transfer energy to Er but also reduce the nonradiative decay of Er, as a result, the emission of Er is enhanced.(3) The effect of annealing on the emission from the Al2O3multilayerThree methods of annealing Al2O3multilayer have been used:1. Rapid thermal annealing for40seconds;2. Normal annealing for30minutes:3. First rapid thermal annealing for40seconds and then normal annealing for30minutes. We have found the more intensified emission can be obtained from the film after two-step annealing. It may be due to the better reduction of nonradiative decay of Er ions by the Si-NCs after the two-step annealing.